Skip to main content
Acta Pharmaceutica Sinica. B logoLink to Acta Pharmaceutica Sinica. B
. 2019 Jan 7;9(2):335–350. doi: 10.1016/j.apsb.2019.01.003

Design, synthesis and biological evaluation of chalcone analogues with novel dual antioxidant mechanisms as potential anti-ischemic stroke agents

Jiabing Wang a,b,, Lili Huang a,c,, Chanchan Cheng a,, Ge Li a,, Jingwen Xie a, Mengya Shen a, Qian Chen a, Wulan Li a,d, Wenfei He a, Peihong Qiu a,, Jianzhang Wu a,
PMCID: PMC6437665  PMID: 30972281

Abstract

Scavenging reactive oxygen species (ROS) by antioxidants is the important therapy to cerebral ischemia-reperfusion injury (CIRI) in stroke. The antioxidant with novel dual-antioxidant mechanism of directly scavenging ROS and indirectly through antioxidant pathway activation may be a promising CIRI therapeutic strategy. In our study, a series of chalcone analogues were designed and synthesized, and multiple potential chalcone analogues with dual antioxidant mechanisms were screened. Among these compounds, the most active 33 not only conferred cytoprotection of H2O2-induced oxidative damage in PC12 cells through scavenging free radicals directly and activating NRF2/ARE antioxidant pathway at the same time, but also played an important role against ischemia/reperfusion-related brain injury in animals. More importantly, in comparison with mono-antioxidant mechanism compounds, 33 exhibited higher cytoprotective and neuroprotective potential in vitro and in vivo. Overall, our findings showed compound 33 could emerge as a promising anti-ischemic stroke drug candidate and provided novel dual-antioxidant mechanism strategies and concepts for oxidative stress-related diseases treatment.

KEY WORDS: Reactive oxygen species, Cerebral ischemia-reperfusion injury, Stroke, Dual-antioxidant mechanism, Chalcones, Antioxidants, Oxidative stress, NRF2/ARE

Graphical abstract

Chalcone analogue 33 conferred protection of PC12 cells against H2O2 insult with novel dual-antioxidant mechanism of directly scavenging reactive oxygen species (ROS) and indirectly through antioxidant pathway activation, and the effect of 33 was more pronounced than that of mono-antioxidant mechanism compounds after MCAO and BCAO in animals.

fx1

1. Introduction

Stroke, becoming one of the leading causes of morbidity and mortality across the world, brings increasingly great pressure to human lives. The large majority (85%) of strokes are ischemic stroke, that is, a stroke resulting from an occlusion of a major cerebral artery, and commonly it occurs in the middle cerebral artery1., 2.. Although remarkable advances have been made in understanding the pathophysiology of cerebral ischemia, effective therapies are still a troubling aspect of human. To date, intravenous thrombolysis has been regarded as an effective strategy for the treatment of acute ischemic stroke3. However, rapid reperfusion accompanied by a large number of reactive oxygen species (ROS) by thrombolytic therapies, could exacerbate brain injury, namely cerebral ischemia-reperfusion injury (CIRI). Among a series of mechanisms related to the pathogenesis of CIRI, oxidative stress has been considered as the main reason4., 5.. Oxidative stress, arising from the uncontrolled production of ROS beyond the neutralizing capacity of the various endogenous defense systems, including enzymatic and non-enzymatic matters, leads to cerebral cell apoptosis and neuronal damage6., 7., 8.. Therefore, exogenous supplementation of antioxidants with ROS scavenging activity would be a potential therapy to cerebral ischemia-reperfusion injury prevention.

Currently, there are two main classes of antioxidants based on the mechanism of inhibiting ROS: (1) compounds that can directly react with ROS are the so-called direct antioxidants, which have the ability to break down the procession of radical chain reactions, like edaravone, resveratrol, quercitin and so on9., 10., 11.. (2) Indirect antioxidants are compounds that do not directly react with ROS but are involved in activating cellular endogenous antioxidant signaling pathways and promoting the transcription of a broad range of cytoprotective genes to remove ROS, where KEAP1/NRF2/ARE is one of the important antioxidative signaling pathways. Many indirect antioxidants, such as TBHQ, curcumin and sulforaphane, that modify cysteine residues in the protein KEAP1, cause the dissociation of NRF2 from the inhibitory partner KEAP1 and facilitate NRF2 to translocate into the nucleus, where NRF2 binds to the antioxidant-responsive element (ARE) consensus sequence to activate the transcription of a panel of cytoprotective genes (phase II genes)9., 11., 12., 13.. Despite extensive research on these two types of antioxidants, most antioxidants have been unsuccessful for clinically treating stroke except edaravone and other very few antioxidants. Moreover, direct and indirect antioxidants are not particularly effective in treating cerebral ischemia-reperfusion injury, which may be related to its own "birth defects". Direct antioxidants are short-lived, which may need to be continually provided to halt the process of cerebral ischemia-reperfusion injury11. While stimulation of cellular endogenous antioxidant defense pathways by indirect antioxidants require a certain time, and during the period of time before activating the pathway, there is a risk that the brain would be irreversibly damaged by ROS insult, since indirect antioxidants itself could not remove ROS immediately. Besides, up till now, there have been no reports about "dual-antioxidant mechanism action" for antioxidant therapy via both directly and indirectly scavenging ROS. Moreover, it is not clear whether antioxidants with dual-antioxidant mechanism may have a better prospect than the ones with mono-antioxidant mechanism for cerebral ischemia-reperfusion injury therapy. Herein, we hypothesized that antioxidant agents with ROS scavenging activity directly and indirectly may be more effective therapeutic strategies for stroke treatment.

Natural products and their synthetic analogues have been shown to be invaluable resources in drug discovery14., 15., 16.. Chalcones or (E)-1,2-diphenyl-2-propene-1-ones, make up a group of natural products that attach to the flavonoid family17. They consist in various of flowers, fruits, vegetables, and have been reported to possess many biological properties including antioxidant18., 19., 20., antibacterial21, anticancer22., 23., antiangiogenic24, and anti-inflammatory activities25., 26.. Among all the biological activities, the antioxidant activity has been extensively studied. Given that a number of small molecules bearing polyhydroxyl groups exhibit a great efficacy in antioxidant activity due to their potent abilities to scavenge ROS directly27., 28., 29., 30., and it is well-known that the electrophilic α,β-unsaturated ketone moiety (Michael acceptor) on a chalcone can result in activation of the NRF2 pathway31, polyhydroxychalcones thus may be considered as monomers to study the potential of double antioxidative properties. In the study, we reported a number of novel (E)-3,4-dihydroxychalcone analogues as anti-ischemic stroke agents that attenuate oxidative stress by directly scavenging ROS and indirectly through KEAP1/NRF2/ARE pathway activation, leading to massive ROS elimination and subsequent inhibition of the ischemia-reperfusion-related brain injury in animals.

2. Results

2.1. Design and synthesis of chalcone analogues

Previous studies have demonstrated that chalcone-based compounds are involved in the indirect antioxidant effect via activation of the NRF2/ARE pathway31. Polyphenols are considered as an appropriate structural element for designing direct antioxidant compounds, especially compounds bearing 3,4-dihydroxyl substituents on benzene ring showed potent free radical scavenging effects32. Besides, the presence of the α,β-double bond on chalcone could increase the stabilization of the phenolic radical32. Therefore, chalone analogues containing 3,4-dihydroxyl substituents may show effective direct and indirect antioxidant activities. In present study, a series of (E)-3,4-dihydroxychalcones and corresponding dimethoxychalcones derivatives as control compounds were synthesized. Furthermore, in order to explore whether 3,4-dihydroxyl substituents in the “A” or “B” ring of chalcones have different effects on antioxidant activity, different moieties were introduced on one benzene ring, while another benzene ring retained the 3,4-dihydroxyl substituents.

The synthetic profiles of the compounds and their chemical structures are listed in Scheme 1 and Table 1. The target chalcone-based compounds were synthesized by the Claisen—Schmidt condensation with NaOH or HCl as catalyst in good yield by a known literature method33., 34., 35.. In summary, substituents such as halogen, amidogen, methoxyl and ethyoxyl were catalyzed by NaOH, and others such as hydroxyl were catalyzed by HCl. The purity was determined by TLC, and the products were characterized by analysis and comparison of their spectral and physical data including HR-MS, 1H NMR and 13C NMR. The color, melting point, HR-MS, 1H NMR and 13C NMR spectrum of novel and unpublished compounds were presented in the chemical section.

Scheme 1.

Scheme 1

Synthesis of chalcone derivatives 141. Reagents and conditions: EtOH, 40% NaOH or HCl, room temperature, 12–24 h.

Table 1.

The structures of chalcone derivatives 141.

Compd. R in A-ring R′ in B-ring Compd. R in A-ring R′ in B-ring
1 3,4-OH 3-OH 22 3,4-OCH3 3,5-F
2 3,4-OCH3 3-OH 23 4-OCH3 3,4-OH
3 3,4-OH 4-NH2 24 4-OCH3 3,4-OCH3
4 3,4-OCH3 4-NH2 25 3-OH, 4-OCH3 3,4-OH
5 3,4-OH 4-OCH3 26 3-OH, 4-OCH3 3,4-OCH3
6 3,4-OCH3 4-OCH3 27 2,4-OCH3 3,4-OH
7 3,4-OH 4-OCH2CH3 28 2,4-OCH3 3,4-OCH3
8 3,4-OCH3 4-OCH2CH3 29 2-OCH3 3,4-OH
9 3,4-OH 4-Cl 30 2-OCH3 3,4-OCH3
10 3,4-OCH3 4-Cl 31 2,3-OCH3 3,4-OH
11 3,4-OH 2-F 32 2,3-OCH3 3,4-OCH3
12 3,4-OCH3 2-F 33 2,5-OCH3 3,4-OH
13 3,4-OH 2-Cl 34 2,5-OCH3 3,4-OCH3
14 3,4-OCH3 2-Cl 35 4-Cl 3,4-OH
15 3,4-OH 4-F 36 4-Cl 3,4-OCH3
16 3,4-OCH3 4-F 37 3,4-Cl 3,4-OH
17 3,4-OH 3,4-F 38 3,4-Cl 3,4-OCH3
18 3,4-OCH3 3,4-F 39 3,4,5-OCH3 3,4-OH
19 3,4-OH 3,4-OCH3 40 3,4,5-OCH3 3,4-OCH3
20 3,4-OCH3 3,4-OCH3 41 3,4-OCH3 3,4-OH
21 3,4-OH 3,5-F

2.2. Protection of chalcone derivatives from H2O2-induced damage in PC12 cells

Hydrogen peroxide (H2O2) as an endogenous cellular signaling molecule could generate exogenous free radicals immediately, which are able to induce lipid peroxidation, and proteins and nucleic acid oxidation, and ultimately lead to cell death36., 37.. Therefore, we evaluated chalcone analogues as potential cytoprotective agents against H2O2-mediated cell damage in a neuron-like cell line, PC12 cells.

Pre-incubation with antioxidants for a long time (more than 6 h), the antioxidants could stimulate endogenous antioxidant defense systems against ROS38., 39.. The cells were pretreated by the tested compounds for 24 h, and then treated with H2O2 insult could be accepted as an experimental method for studying antioxidant activity39., 40., 41., 42., 43.. Therefore, to study cytoprotection activity of compounds, the screening model of pre-incubation for 24 h was used in this test first. Quercetin, edaravone (ED) and TBHQ are well-known antioxidants, which are used as the positive controls. As shown in Fig. 1A, some (E)-3,4-dihydroxychalcones exhibited good protective efficacy, while only a few (E)-3,4-dimethoxychalcones displayed weak cytoprotection. Surprisingly, among these (E)-3,4-dihydroxychalcones, chalcones with 3,4-dihydroxyl groups on ring “A”, electron donating groups or electron withdrawing groups on ring “B”, all displayed potent cytoprotection. Moreover, compared with quercetin, ED and TBHQ, compounds 23, 25, 29, 31, 33, 37, 39 and 41 exerted greater cytoprotection effects. However, only compounds 7, 13 and 19 bearing 3,4-dihydroxyl substituents on ring “B” had cytoprotection activity.

Figure 1.

Fig. 1

Compounds׳ cytoprotection on PC12 cells in H2O2 damage model and DPPH radical scavenging activities of chalcone analogues. PC12 cells were pretreated for 24 h (A) or 1 h (B) with chalcone analogues (10 μmol/L), then another 24 h exposure in H2O2 (450 μmol/L), finally determined by the MTT assay. The viability of untreated cells is defined as 100%. (C) DPPH radical scavenging rate of chalcone derivatives (20 mg/L). Data are expressed as the mean±SD (n=3). #P<0.05 significantly different from control group, *P<0.05 significantly different from H2O2 group.

In general, due to the pretreatment with antioxidants for a short time (within 2 h) followed by H2O2 insult, there is not enough time to induce the expression of cytoprotective protein, and antioxidants may play cytoprotective effect by directly neutralizing ROS44. Thus, we chose the screening model of compounds pre-incubation for 1 h to further study the free radical scavenging activity. Notably, all (E)-3,4-dihydroxychalcones were capable of relieving the cell injury induced by H2O2 insult, whereas the (E)-3,4-dimethoxychalcones exhibited no cytoprotection (Fig. 1B).

To further validate their direct free radical scavenging activity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was further applied in the test45. As shown in Fig. 1C, as expected, chalcone analogues bearing 3,4-dihydroxyl substituents on ring “A” or “B” all exhibit significant ability to scavenge free radicals directly. In contrast, (E)-3,4-dimethoxychalcones were found to be inactive. The result was in line with the damage model with compounds pre-incubation for 1 h, which showed compounds might execute their cytoprotection through scavenging free radicals directly.

More interestingly, compound 21 showed cytoprotection activity only in the model of pre-incubation for 1 h, which suggested that its antioxidant mechanism may via directly removing free radicals. Compounds 7, 13, 19, 23, 25, 27, 29, 31, 33, 35, 39 and 41 were found to have good advantages for cytoprotection at both time points, and thus these compounds may act as both “direct” and “indirect” antioxidants.

2.3. Compound 33 with dual-antioxidant mechanism showed better antioxidant activity than compounds with mono-antioxidant mechanism in vitro

So far, compared with antioxidants with mono-antioxidant mechanism, there are no reports about whether those with dual-antioxidant mechanism may have better drug prospects. Based on the promising cytoprotection activity, compound 33 could be considered as a direct and indirect antioxidant. Thus, 33 was selected as the candidate compound with dual-antioxidant mechanism for further investigation. In addition, the molecules that have similar structure to 33 are chosen as control compounds with mono-antioxidant mechanism. Compound 21 mentioned above may be a free radical scavenger. Furthermore, (E)-3,4-dimethoxychalcones without phenolic hydroxy showed no effective cytoprotection activity in the study, which suggested that there may be no indirect antioxidants. In our previous study, chalcone derivatives were found to act as antioxidants by activating the antioxidant NRF2 signaling pathway, and compound 1b without phenolic hydroxy pretreatment for 24 h had an ability to protect against H2O2-triggered cell apoptosis43 (Supporting Information Fig. S1). After pre-incubation with 1b for 1 h followed by H2O2 insult, the population of viable cells did not increase (Supporting Information Fig. S1), which means 1b may execute the antioxidant activities mainly through activating antioxidant signaling pathway. Immunofluorescence experiments also revealed that NRF2 nuclear translocation was activated by compounds 33 and 1b, rather than by compound 21 (Fig. 3A and Supporting Information Fig. S2). In order to confirm whether compounds 33, 1b and 21 could stimulate the related protein coding genes expression in the NRF2-ARE signaling pathway, Western blot experiments were further determined. As showed in Fig. 2C, compound 21 could not upregulate HO-1 protein expression in PC12 cells, while both compounds 33 and 1b could elevate HO-1 level. Therefore, according to the above results, compound 33 was proven as a both “direct” and “indirect” antioxidant, while compounds 21 and 1b were deemed as a free radical scavenger and an activator of cellular antioxidant pathway, respectively, and were used as the control compounds with mono-antioxidant mechanism.

Figure 3.

Fig. 3

Compound 33 activated the antioxidant defense system in PC12 cells. (A) 33 promoted NRF2 translocation into the nucleus. PC12 cells were incubated with 33, ED and TBHQ at 10 μmol/L for 6 h, and then stained with NRF2 antibody and DAPI. (B) and (C) 33 induced the mRNA expression of GCLC and HO-1. PC12 cells were incubated with 33 in different doses for 24 h and then evaluated the mRNA level of GCLC and HO-1 by RT-PCR experiment. (D) 33 induced the protein expression of GCLC and HO-1. PC12 cells were incubated with 33 at 2.5, 5 and 10 μmol/L, TBHQ at 10 μmol/L for 24 h, and the GCLC and HO-1 were determined by Western blot experiment. (E) BSO or ZnPP diminished the protected effect of 33 on H2O2 induced cell damage. PC12 cells were incubated with GCLC inhibitor BSO or HO-1 inhibitor ZnPP for 1 h, then treated with 33 (10 μmol/L) for 24 h and exposed to H2O2 (450 μmol/L) for additional 24 h. Finally, MTT assay measured the OD values in 490 nm. Data are expressed as the mean ± SD (n=3). ###P<0.001, ##P<0.01, #P<0.05 significantly different from control group, ***P < 0.001, *P < 0.05.

Figure 2.

Fig. 2

The cytoprotective effects of 33 on PC12 cells subjected to H2O2. (A) Cytotoxicity screening of 33 in PC12 cells. The cells were treated with 10 μmol/L of 21, 33 and 1b for 24 h, and the cytotoxicity of compounds were determined by the MTT assay. (B) Protection of compound 33 against H2O2-induced PC12 cell damage. PC12 cells were incubated with 10 μmol/L of 33, 21, 1b for 1, 2, 4, 6, 9,12, 15, 18, 21 and 24 h before exposed to H2O2 (450 μmol/L) for additional 24 h. Then the cell viability was determined by MTT assay. (C) Elevating the expression level of protein HO-1 by 33. PC12 cells were incubated with 33 (10 μmol/L), 21(10 μmol/L), 1b (10 μmol/L) for 2, 6, 12,18 and 24 h, and the HO-1 was determined by Western blot experiment. (D) 33 protected PC12 cells from H2O2-induced cell injury. PC12 cells were pretreated with 33 in different doses (2.5, 5 and 10 μmol/L) for 1 or 24 h, then treated with 450 μmol/L H2O2 for 24 h, and determined by the MTT assay. (E) 33 decreased ROS level in H2O2-treated PC12 cells. PC12 cells were pre-treated with 10 μmol/L of 33, ED or TBHQ, then treated with H2O2 for 4 h, and the ROS level was measured by flow cytometry. (F) Protection of compound 33 by reducing MDA. PC12 cells were pre-incubated with 33 at 2.5, 5 and 10 μmol/L, ED (10 μmol/L) or TBHQ (10 μmol/L) for 1 or 24 h, then treated with 700 μmol/L H2O2 for 16 h, finally determined by the manufacturer׳s instructions. Data are expressed as the mean±SD (n=3). ###P<0.001, ##P<0.01, #P<0.05 significantly different from control group, ***P<0.001, **P<0.01, *P<0.05 significantly different from H2O2 group.

Generally speaking, ideal antioxidant agents have lower toxicity, so the cytotoxicity of compounds (1b, 21 and 33) toward the PC12 cells were assessed. As shown in Fig. 2A, there is no apparent cytotoxicity of the tested compounds at 10 μmol/L. To compare the antioxidant activity of these compounds, PC12 cells were pretreated with compounds 1b, 21 and 33 for 10 time points from 1 to 24 h followed by H2O2 challenge. The results showed that compound 33 exhibited potent cytoprotection throughout the incubation time, while compounds 21 and 1b were active only when pretreated for 1–10 h and 9–18 h, respectively, which indicated that compound 33 has better antioxidant activity (Fig. 2B). To explore the different mechanisms of antioxidant activity among compounds 1b, 21 and 33, the expression of HO-1 protein at 0, 2, 6, 12, 18 and 24 h after treatment with compounds in PC12 cells was further determined. As shown in Fig. 2C, 33 and 1b both started to activate the expression of HO-1 at 12 h and could last continuously to 24 and 18 h, respectively, whereas 21 could not induce HO-1 expression. Therefore, these data collectively demonstrated that 21 generally relies on the facile ability of phenols to be oxidized to wield its primary cytoprotection effect, while 1b was involved in endogenous cellular NRF2 signaling pathway to diminish oxidative damage. Taken together, compared with mono-antioxidant mechanism compound, 33 displayed better protection in vitro.

In order to further determine the potential interest of 33 as a cytoprotective agent, PC12 cells were pretreated with 33 for 1 or 24 h, and incubated with H2O2 for another 24 h. As shown in Fig. 2D, the population of viable cells increased in a dose-dependent manner. The burst of ROS is unavoidable when cells are stimulated with H2O2. To confirm the ROS scavenging activity of 33, we further determined the content of ROS after H2O2 insult. As shown in Fig. 2E, pretreatment of the cells with 33 for 1 or 24 h remarkably reduced the ROS accumulation. Malondialdehyde (MDA), a byproduct of polyunsaturated fatty acid peroxidation caused by ROS, is regarded as a significant biomarker of oxidative stress46. It is found that addition of 33 for 1 or 24 h significantly reduced the MDA in a dose-dependent manner (Fig. 2F). Consequently, compound 33 significantly protected PC12 cells from H2O2-induced cell injury.

2.4. Activation of NRF2-ARE pathway is responsible for the antioxidant activities of compound 33

When NRF2 is activated, it translocates into the nucleus and thus further exerts its transcriptional function. Hence, we examined whether compound 33 can induce the nucleus translocation of NRF2 in PC12 cells by immunofluorescence. ED and TBHQ were used as positive controls. The blue and red staining represent nuclei and NRF2, respectively, and merge represents both. As shown in Fig. 3A, compared to the blank control group, there was strong fluorescent light in the nucleus, clearly showing that 33 could induce NRF2 translocation and concentration in the nucleus. Authentically, the similar phenomenon occurred when treated with TBHQ and ED. The results supported that 33 was able to promote NRF2 to accumulate in the nuclei.

NRF2 can initiate the transcription of phase II genes, the expression of GCLC and HO-1 were further determined. First of all, the GCLC and HO-1 mRNA expression levels induced by 33 were investigated by RT-PCR. As shown in Fig. 3B–C, 33 clearly increased the GCLC and HO-1 mRNA levels in a dose-dependent manner. The data showed compound 33 treatment could effectively activate the transcription of NRF2-driven antioxidant genes. Furthermore, to elucidate the mechanism of 33, Western blot assays were used to determine the expression levels of GCLC and HO-1. After PC12 cells were treated with 33 at 2.5, 5 and 10 μmol/L levels for 24 h, the expression of GCLC and HO-1 protein enhanced in a concentration-dependent manner (Fig. 3D). Especially, 33 at 5 μmol/L exhibited much stronger promoting effects than TBHQ at 10 μmol/L.

To make sure if the expression of GCLC and HO-1 caused by the 33 is responsible for the cytoprotective effects against H2O2-derived oxidative cell death, BSO and ZnPP, which are specific inhibitors of GCLC and HO-1 respectively, were utilized in this study43., 44., 47.. As shown in Fig. 3E, after PC12 cells were pre-treated with ZnPP (15 μmol/L) or BSO (10 μmol/L) for 1 h, there is no obvious adverse effects on the viability of PC12 cells. Applying 33 alone raised the cell viability, while BSO or ZnPP all can cause a dramatic decrease in cell viability induced by 33. These results suggested that promotion NRF2 translocation into the nucleus and further induction of GCLC and HO-1 expression had a significant function in hindering oxidative stress, and at least partly, explaining the antioxidant activity of 33. In all, according to the results in vitro, it seems that compound 33 is an ROS scavenger and an activator of cellular intrinsic KEAP1/NRF2/ARE antioxidant pathway at the same time.

2.5. Protective effect of compound 33 was more pronounced than that of mono-antioxidant mechanism compound on cerebral ischemia-reperfusion injury

Inspired by the results above, 33 showed significantly higher protection of PC12 cells against oxidative insults through dual antioxidant mechanisms in vitro. However, it is still not clear that whether 33 has a better protection than the mono-antioxidant mechanism compound for inhibiting cerebral ischemia-reperfusion injury. Hence, the neuroprotective activity of 33 in vivo was further investigated in a rat model of transient focal cerebral ischemia by intraluminal occlusion of the middle cerebral artery (MCAO), which was considered to be the most common reason for inducing I/R-related brain injury in the clinic48. Considering that administration of various drugs by intraperitoneal or intravenous injection exists different absorption, distribution, metabolism and excretion (ADME), which could disturb their efficacy, the anti-ischemic stroke effects of 33, 21 and 1b were evaluated by pre-injection into lateral ventricles in order to exclude the effect of peripheral pharmacokinetics of drugs. The infarct size of individual rat was evaluated by the 2,3,5-triphenyltetrazolium chloride (TTC) staining49. As illustrated in Fig. 4A–B, as expected, there were no obvious neuronal abnormality in the sham group, whereas the infarct area in the model group and vehicle group of rats significantly increased, as shown in the white region of rat brain sections. But, intracerebroventricular administration of 33 markedly reduced the infarct sizes of I/R rats. Additionally, treatment with 33 improved the neurologic scoring in the brains from ischemic rats. The addition of 21 and 1b were found to show weak protective effects on infarction damage, respectively (Fig. 4C). Therefore, the effect of 33 was more pronounced than that of 21 and 1b, which was in accordance with the cell-based results. It suggested that the compound with dual antioxidant mechanism may have more potential for the treatment of ischemic brain damage compared with the compound with mono-antioxidant mechanism.

Figure 4.

Fig. 4

Protective effect of compounds 33, 21 and 1b on brain infarct after 72 h reperfusion. (A) TTC staining analysis of the infarcted brain regions. (B) Quantitative analysis of the infracted brain regions. The ratios of infarct area to whole brain areas in individual rats were calculated. (C) Quantitative analysis of neurological score. Cerebral infarction in Sham-operated (Sham) or MACO-reperfusion rats from a representative animal that received normal saline (NS), Veh (polymer:DMSO:distilled water at 50 mg:1 mL:3 mL), or 33-nanoparticles (0.2 mg/kg), 21-nanoparticle (0.2 mg/kg), and 1b-nanoparticles (0.2 mg/kg) intracerebroventricularly 2 h before MCAO. Data are expressed as the mean±SD (n=3). ###P < 0.001 significantly different from Sham group, ***P< 0.001, *P < 0.05 significantly different from control group.

2.6. Therapeutic effects of compound 33 on cerebral ischemia-reperfusion injury

To date, in addition to preventative therapies for stroke, there has been a more important need to develop effective therapeutic therapies in clinic. Within 3—6 h after stroke onset has been considered as prime time against brain ischemia50., 51.. Therefore, we next evaluated the therapeutic characteristics of 33 in exerting its effectiveness 3 and 6 h following ischemia-reperfusion injury. To demonstrate the cerebral therapeutic effects of compound 33, MCAO rat model was also used in this study. Edaravone as a direct antioxidant has been demonstrated to show therapeutic effects on ischemic stroke in the clinic and was used as positive control. Similarly, from the results of TCC staining and neurological scoring, 33 showed more significant therapeutic effect than edaravone when administration conducted 3 or even 6 h after I/R induction (Fig. 5A–C).

Figure 5.

Fig. 5

Therapeutic effect of compound 33 on cerebral ischemia-reperfusion injury. (A) TTC staining analysis of the infarcted brain regions. Quantitative analysis of the infracted brain regions (B) and neurological score (C). (D) and (E) The locomotion trace of the mice in the chamber for a period of 5 min. All animals were divided into seven groups: sham-operated group, NS group, Veh (Cremophor:PBS at 3:97) group. 33 (15 mg/kg, 3 h) + MCAO group, 33 (15 mg/kg, 6 h) + MCAO group, ED (15 mg/kg, 3 h) + MCAO group and ED (15 mg/kg, 6 h) + MCAO group. All rats received drug intraperitoneally 3 or 6 h after MCAO. Data are expressed as the mean±SD (n=3). ###P<0.001, ##P<0.01 significantly different from Sham group, ***P < 0.001, **P<0.01, *P< 0.05 significantly different from control group.

Cerebral ischemia is known to produce severe behavioral deficits, and bilateral cerebral artery occlusion (BCAO), as another model, was applied for evaluating its protection activity by open field test to estimate locomotor activity of the tested mice. Their total distance of the in-between 5 min traveled during the observation period was collected and analyzed. As shown in Fig. 5D–E, no obvious ischemia-induced barriers to behavior were observed in sham-operated group. However, the I/R model and vehicle-treated group of mice showed prominent behavioral deficits and the locomotor activity decreased markedly compared with the sham-operated group. In contrast, the neurobehavioral function of compound 33 or edaravone treated mice had obviously improved at 3 h after cerebral ischemia-reperfusion injury. Especially, when intraperitoneal injection of 33 even 6 h after I/R onset, it still had dramatic improvement in exercise behavior, which had even much stronger protective effect than edaravone. In all, these data showed that compound 33 could emerge as a promising anti-ischemic stroke drug candidate.

3. Discussion

Excessive production of ROS is known to lead to acute ischemic injury in various organs, and numerous studies have demonstrated antioxidant therapy is considered as an effective strategy in ischemic disorders52., 53., 54., 55., 56.. For the current status of antioxidants, this research not only offers novel dual-antioxidant mechanism strategies and concepts on oxidative stress-related diseases treatment, but also provides promising candidate antioxidant drugs with dual-antioxidant mechanism.

Attenuation acute ischemic injury can be mediated by direct and indirect antioxidants. Among them, N-acetylcysteine (NAc) has been extensively used as a powerful ROS scavenger and potent neuroprotective actions for the treatment of acute ischemic stroke and rhabdomyolysis-induced acute kidney injury in animal models, respectively57., 58.. As for indirect antioxidants, such as tert-butylhydroquinone, which has been shown to enhance NRF2 signaling activity and protect against ROS in various brain cells in vitro59., 60., 61.. Comparing the direct and indirect antioxidants, the study of Jokod showed that indirect antioxidants were more beneficial for cytoprotection than direct antioxidants in vitro62. Moreover, some antioxidants, including melatonin and resveratrol, appear to play a dual-antioxidant protective role as direct and indirect antioxidants63., 64., 65..

Up till now, there was no study about whether the compounds with dual-antioxidant mechanism may have a better prospect than the ones with single-antioxidant mechanism in acute ischemic stroke. In the present study, compound 33 not only scavenged ROS directly, but also activated NRF2 pathway, and thus it could be considered a both direct and indirect antioxidant. Notably, when PC12 cells were pretreated with 33 for 10 time points from 1 to 24 h followed by H2O2 insult, 33 exhibited excellent cytoprotection at all the incubation time. For mono-antioxidant compounds, when pretreated with compound 21 as direct antioxidant, the cytoprotection against H2O2 lasted 1–10 h, and when pretreatment with compound 1b as indirect antioxidant showed cytoprotection only for 9–18 h. Furthermore, interestingly, compound 33 showed a preferable role for neuroprotecting against cerebral ischemia-reperfusion injury in animal models compared with compounds 21 and 1b. Taken together, all results suggested that drugs with dual-antioxidant mechanism might be more pronounced than that with single-antioxidant mechanism, which could provide novel and promising strategies and concepts for drug research on antioxidant and stroke treatment.

Natural or synthetic bioactive chalcones have attracted enormous attention in drug exploration due to their low toxicity and various biological activities, especially since they were found to prevent oxidative stress-induced neurodegenerative disorders. For instance, xanthohumol showed protection against oxidative damage in PC12 cells via activating NRF2 enzymes38. The study of Jeon also demonstrated chalcone derivatives displayed neuroprotective effects against oxidative stress-induced apoptosis in SH-SY5Y cells66. In our present study, after treatment with chalcone analogue 33 in both BCAO and MCAO models, all exhibited significant protective effects. Divertingly, compound 33 exerted higher central protection than edaravone at the same dose when administration conducted 3 or even 6 h after I/R induction. Therefore, 33 could serve as a potent candidate antioxidant drug for anti-ischemic stroke drug research and other ischemic disorders treatment.

Phenolic compounds possess high antioxidant activity and are potent regulators of cellular redox status, which have been frequently considered as potent antioxidants. Natural chalcones bearing 3,4-dihydroxyl groups, such as butein, sappanchalcone and okanin, are particularly effective antioxidants67., 68., 69.. Chiruta et al.70 reported chalcone derivatives containing catechol group contributed to neuroprotective activity and maintenance of GSH. In addition, Dziedzic et al.71 revealed that molecules bearing ortho-dihydroxyl possess significantly higher antioxidant activity than those bearing no such functionalities, which may be due to the abstraction of the two hydrogen atoms of the ortho-position hydroxyls respectively, to form a quinone structure. Benayahoum et al.72 reported the great reactivity of the ortho-dihydroxyl system is possibly due to the smaller dissociation energy of the O-H bond. Moreover, compounds including 3,4-dihydroxyl groups on benzene ring were found to be more potent antioxidant than resveratrol73. Hence, chalcone derivatives bearing 3,4-dihydroxyl are favorable for the development of effective antioxidants.

In our study, chalcone analogues bearing 3,4-dihydroxyl groups on ring “A” or ring “B” were designed and synthesized. After PC12 cells were pretreated with (E)-3,4-dihydroxychalcones for a short time (1 h) followed by H2O2 challenge, all compound markedly promoted cell viability, while chalcone derivatives bearing a hydroxyl group or no hydroxyl group remained inactive. Additionally, the results of DPPH assay confirmed the above results, which suggested the (E)-3,4-dihydroxychalcones could scavenge ROS directly. When pretreated for 24 h, there are many 3,4-dihydroxychalcone derivatives showing advantageous cytoprotection. Interestingly, compared with 3,4-dihydroxyl groups on ring “B”, chalcone analogues with 3,4-dihydroxyl groups on ring “A” all showed significant cytoprotection and had a great improvement on antioxidant capacity, which suggested that the presence of 3,4-dihydroxyl groups on ring “A” may be good for antioxidant activity. Given that the number of (E)-3,4-dihydroxychalcones is limited, further research is needed to establish a clearer quantitative structure—activity relationship between structure and cytoprotection with more compounds. Furthermore, compound 33 containing 3,4-dihydroxyl groups on ring “A” with the best antioxidant activity was screened out, and further study showed that 33 could activate NRF2 pathway. So hypothetically, stimulating NRF2 pathway may also occurred in other cytoprotective chalcone analogues containing 3,4-dihydroxy groups on “A” ring. Taken together, chalcone analogues with 3,4-dihydroxyl groups on ring “A” presented important neuroprotective activity via directly scavenging ROS and indirectly through NRF2 pathway activation. Therefore, (E)-3,4-dihydroxychalcone may be considered as a promising structural element for designing antioxidant compounds with dual-antioxidant mechanism.

4. Conclusions

In the research of antioxidant field, there are no researches on the antioxidant agents with novel dual-antioxidant mechanism of directly scavenging ROS and indirectly through activation of antioxidant pathway. It is also unclear whether antioxidants with dual antioxidant mechanisms have broader application prospects. Our recent research had led to the design and development of a series of antioxidants and found a number of excellent antioxidants with scavenging ROS directly and indirectly. The most potent compound 33 not only showed protection of H2O2-induced oxidative damage in PC12 cells through scavenging free radicals directly and activating NRF2 pathway at the same time, but also played protective and therapeutic roles against ischemia/reperfusion-related brain injury in animals. More importantly, compound 33 were superior to compounds (only free radical scavengers or NRF2 pathway stimulators) both in vitro and in vivo. Thus, our present study found a new candidate drug for cerebral ischemia-reperfusion injury treatment, clarified that the dual antioxidant mechanisms have a better prospect for drug development, and provided new ideas and tactics for drug research on stroke and other oxidative stress-induced diseases treatment.

5. Experimental

5.1. Chemistry

All chemical reagents were obtained commercially from Sigma—Aldrich (St Louis, MO, USA), Aladdin (Shanghai, China) and used without further purification unless otherwise noted. Reactions were monitored by thin-layer chromatography TLC using silica gel GF254, and the chromatograms were conducted on silica gel (200–300 mesh) and observed under UV light at 254 and 365 nm. Melting points (m.p.) are uncorrected and were measured in open capillary tubes on a Fisher—Johns melting apparatus. Mass spectra (MS) were recorded on an Agilent 1100 LC—MS (Agilent, Palo Alto, CA, USA). 1H NMR and 13C NMR spectra were obtained from 600 MHz spectrometer (Bruker Corporation, Switzerland). Chemical shifts are reported in δ units (ppm) relative to TMS as internal standard. Coupling constants (J) are expressed in Hz, and splitting patterns are described as follows: s=singlet; d=doublet; t=triplet; q=quartet; m=multiplet; dd=doublet of doublets; dt=doublet of triplets.

5.1.1. General procedure for the synthesis of chalcones

A mixture of the corresponding acetophenone (1 eq.) and the corresponding aldehyde (1 eq.) in anhydrous EtOH was stirred at room temperature for 5 min. Then NaOH or HCl (gas) was added into the solution to catalyze the reaction. The reaction mixture was stirred at room temperature until aldehyde was consumed (usually 12–24 h). Completion of the reaction was monitored by thin layer chromatography using ethyl acetate/hexanes as the solvent system. The reaction was quenched by pouring into 50 mL of stirring ice water. If the product precipitated out after quenching with cold water, it was filtered off and crystallized with hot ethanol. In other cases, the products were purified by using silica gel chromatography. Compounds 17, 910, 13, 14, 16, 1920, 22, 24, 26, 28, 32, 36, 38 and 40 were published previously in the literature74., 75., 76., 77., 78., 79., 80., 81., 82., 83., 84., 85., 86., 87., 88., 89., and their spectral data are in the Supporting Information. The spectral data of novel or unreported compounds are listed as follows.

(E)-3-(3,4-Dimethoxyphenyl)-1-(4-ethoxyphenyl)prop-2-en-1-one (8): Yellow power, 67.6% yield, m.p. 88.9–93.4 °C. 1H NMR (DMSO-d6) δ 8.165 (d, J=9.0 Hz, 2 H, H-2′, H-6′), 7.839 (d, J=15.5 Hz, 1 H, H-β), 7.683 (d, J=15.5 Hz, 1 H, H-α), 7.544 (s, 1 H, H-2), 7.379 (d, J=8.5 Hz, 1 H, H-5), 7.069 (d, J=9.0 Hz, 2 H, H-3′, H-5′), 7.022 (d, J=8.5 Hz, 1 H, H-6), 4.145 (q, J=7.0 Hz, 2 H, OCH2-4′), 3.877 (s, 3 H, OCH3-3), 3.824 (s, 3 H, OCH3-4), 1.369 (t, J=6.5 Hz, 3 H, CH3); 13C NMR (DMSO-d6) δ 187.25, 162.35, 151.13, 149.53, 143.53, 130.76 (2), 130.56, 127.67, 123.64, 119.62, 114.27 (2), 111.60, 110.82, 63.52, 55.74, 55.58, 14.45. HR-MS m/z 313.1436 [M + H]+, Calcd. for C19H20O4: 312.1362.

(E)-3-(3,4-Dihydroxyphenyl)-1-(2-fluorophenyl)prop-2-en-1-one (11): Yellow green powder, 72.6% yield, m.p. 174.7–175.8 °C. 1H NMR (Acetone-d6) δ 8.581 (s, 1 H, OH-3), 8.255 (s, 1 H, OH-4), 7.760 (dd, J=1.8 Hz, J=7.2 Hz, 1 H, H-6′), 7.633–7.645 (m, 1 H, H-4′), 7.572 (dd, J=1.2 Hz, J=15.6 Hz, 1 H, H-β), 7.331–7.357 (m, 1 H, H-5′), 7.281–7.299 (m, 1 H, H-3′), 7.266 (d, J=1.8 Hz, 1 H, H-2), 7.213 (dd, J=2.4 Hz, J=15.6 Hz, 1 H, H-α), 7.142 (dd, J=2.4 Hz, J=8.4 Hz, 1 H, H-6), 6.904 (d, J=7.8 Hz, 1 H, H-5); 13C NMR (DMSO-d6) δ 188.55, 161.02, 159.02, 149.13, 145.70, 133.73, 130.30, 127.32, 125.71, 124.75, 122.54, 122.09, 116.58, 115.87, 114.97. HR-MS m/z 281.0593 [M + Na]+, Calcd. for C15H11FO3: 258.0692.

(E)-1-(3,4-Dimethoxyphenyl)-3-(2-fluorophenyl)prop-2-en-1-one (12): Yellow powder, 67.4% yield, m.p. 90.5–92.4 °C. 1H NMR (CDCl3) δ 7.591 (d, J=7.8 Hz, 1 H, H-4′), 7.564–7.536 (m, 2 H, H-6′, H-5′), 7.489 (d, J=14.4 Hz, 1 H, H-β), 7.403 (d, J=1.8 Hz, 1 H, H-6), 7.310–7.288 (m, 2 H, H-3′, H-2), 7.188 (d, J=16.2 Hz, 1 H, H-α), 7.002 (d, J=8.4 Hz, 1 H, H-5), 3.809 (s, 6 H, OCH3-3, OCH3-4); 13C NMR (DMSO-d6) δ 187.93, 151.45, 149.04, 145.01, 137.81, 136.51, 130.29 (2), 128.77 (2), 127.40, 124.07, 119.28, 111.58, 110.93, 55.75, 55.59. HR-MS m/z 287.1071 [M + H]+, Calcd. for C17H15FO3: 286.1005.

(E)-3-(3,4-Dihydroxyphenyl)-1-(4-fluorophenyl)prop-2-en-1-one (15): Yellow power, 78.8% yield, m.p. 224.4–226.0 °C. 1H NMR (Acetone-d6) δ 8.594 (s, 1 H, OH-3), 8.212 (t, J=1.8 Hz, 2 H, H-3′, H-5′), 8.151 (s, 1 H, OH-4), 7.687 (d, J=15.6 Hz, 1 H, H-β), 7.624 (d, J=15.6 Hz, 1 H, H-α), 7.336 (d, J=1.8 Hz, 1 H, H-2), 7.298 (t, J=8.7 Hz, 2 H, H-2′, H-6′), 7.210 (t, J=8.4 Hz, 1 H, H-6), 6.905 (d, J=8.4 Hz, 1 H, H-5); 13C NMR (DMSO-d6) δ 191.01, 152.10, 148.76, 145.85, 145.58, 145.11, 131.24, 131.16, 128.86, 126.21, 124.40, 122.23, 118.19, 115.50, 114.40. HR-MS m/z 281.0593 [M + Na]+, Calcd. for C15H11FO3: 258.0692.

(E)-1-(3,4-Difluorophenyl)-3-(3,4-dihydroxyphenyl)prop-2-en-1-one (17): Yellow power, 77.9% yield, m.p. 234.9–236.4 °C. 1H NMR (DMSO-d6) δ 9.803 (s, 1 H, OH-3), 9.123 (s, 1 H, OH-4), 8.178–8.214 (m, 1 H, H-2′), 8.019–8.037 (m, 1 H, H-6′), 7.600–7.667 (m, 1 H, H-5′), 7.654 (d, J=16.2 Hz, 1 H, H-β), 7.628 (d, J=16.2 Hz, 1 H, H-α), 7.302 (d, J=2.4 Hz, 1 H, H-2), 7.218 (dd, J=2.4 Hz, J=8.4 Hz, 1 H, H-6), 6.819 (d, J=8.4 Hz, 1 H, H-5); 13C NMR (DMSO-d6) δ 186.38, 149.00, 145.80, 145.60, 126.16, 125.99, 125.93, 122.49, 117.92, 117.78, 117.74, 117.67, 117.53, 115.82, 115.70. HR-MS m/z 277.0682 [M + H]+, Calcd. for C15H10F2O3: 276.0598.

(E)-1-(3,4-Difluorophenyl)-3-(3,4-dimethoxyphenyl)prop-2-en-1-one (18): Yellow power, 75.0% yield, m.p. 118.6–120.4 °C. 1H NMR (CDCl3) δ 7.846–7.880 (m, 1 H, H-6′), 7.801–7.809 (m, 1 H, H-2′), 7.788 (d, J=15.6 Hz, 1 H, H-β), 7.309 (d, J=15.6 Hz, 1 H, H-α), 7.262–7.311 (m, 1 H, H-5′), 7.248 (dd, J=1.8 Hz, J=8.4 Hz, 1 H, H-6), 7.156 (d, J=1.8 Hz, 1 H, H-2), 6.913 (d, J=7.8 Hz, 1 H, H-5), 3.976 (s, 3 H, OCH3-3), 3.945 (s, 3 H, OCH3-4); 13C NMR (DMSO-d6) δ 182.45, 146.59, 144.15, 140.69, 122.32, 120.00, 119.94, 118.18, 113.59, 112.58, 112.44, 112.26, 112.12, 106.00, 105.04, 50.78 (2). HR-MS m/z 305.0982 [M + H]+, Calcd. for C17H14F2O3: 304.0911.

(E)-1-(3,5-Difluorophenyl)-3-(3,4-dihydroxyphenyl)prop-2-en-1-one (21): Yellow powder, 46.6% yield, m.p. 180.9–183.2 °C. 1H NMR (Acetone-d6) δ 7.729–7.764 (m, 3 H, H-β, H-2′, H-6′), 7.672 (d, J=15.6 Hz, 1 H, H-α), 7.379 (d, J=1.8 Hz, 1 H, H-2), 7.305 (dd, J=2.4 Hz, J=8.4 Hz, 1 H, H-4′), 7.251 (dd, J=1.8 Hz, J=7.8 Hz, 1 H, H-6), 6.912 (d, J=7.8 Hz, 1 H, H-5); 13C NMR (DMSO-d6) δ 191.00, 152.10, 149.17, 146.44, 145.86, 145.60, 128.86, 126.12, 124.39, 122.71, 117.68, 115.95, 115.70, 115.50, 114.40. HR-MS m/z 277.0682 [M + H]+, Calcd. for C15H8F2O3: 276.0598.

(E)-1-(3,4-Dihydroxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one (23): Yellow crystal, 81.6% yield, m.p. 129.3–132.3 °C. 1H NMR (CDCl3) δ 7.800 (d, J=9.0 Hz, 2 H, H-2, H-6), 7.698 (d, J=15.0 Hz, 1 H, H-β), 7.614 (d, J=15.0 Hz, 1 H, H-α), 7.607 (dd, J=2.4 Hz, J=8.4 Hz, 1 H, H-6′), 7.499 (d, J=2.4 Hz, 1 H, H-2′), 7.002 (d, J=9.0 Hz, 2 H, H-3, H-5), 6.850 (d, J=8.4 Hz, 1 H, H-5′), 3.814 (s, 3 H, OCH3-4); 13C NMR (DMSO-d6) δ 187.14, 161.04, 150.66, 145.41, 142.32, 130.46×2, 129.84, 127.54, 121.87, 119.74, 115.40, 115.17, 114.36 (2), 55.32. HR-MS m/z 271.0995 [M + H]+, Calcd. for C16H14O4: 270.0892.

(E)-1-(3,4-Dihydroxyphenyl)-3-(3-hydroxy-4-methoxyphenyl)prop-2-en-1-one (25): Yellow powder, 43.5% yield, m.p. 153.8–156.6 °C. 1H NMR (DMSO-d6) δ 7.601 (d, J=3.6 Hz, 1 H, H-β), 7.583 (t, J=5.4 Hz, 1 H, H-6′), 7.530 (d, J=15.6 Hz, 1 H, H-α), 7.491 (d, J=2.4 Hz, 1 H, H-2′), 7.273 (d, J=1.8 Hz, 1 H, H-2), 7.247 (dd, J=2.4 Hz, J=2.4 Hz, 1 H, H-6), 6.987 (d, J=6.4 Hz, 1 H, H-5′), 6.855 (d, J=7.8 Hz, 1 H, H-5), 3.835 (s, 3 H, OCH3-4); 13C NMR (DMSO-d6) δ 187.12, 150.70, 149.97, 146.65, 145.40, 142.82, 129.86, 127.85, 121.79, 121.56, 119.55, 115.31, 115.08, 114.62, 111.98, 55.66. HR-MS m/z 287.0914 [M + H]+, Calcd. for C16H14O5: 286.0841.

(E)-1-(3,4-Dihydroxyphenyl)-3-(2,4-dimethoxyphenyl)prop-2-en-1-one (27): Yellow powder, 43.9% yield, m.p. 191.3–192.9 °C. 1H NMR (DMSO-d6) δ 7.928 (d, J=15.6 Hz, 1 H, H-β), 7.819 (d, J=15.6 Hz, 1 H, H-α), 7.626 (dd, J=3.0 Hz, J=2.4 Hz, 1 H, H-6), 7.505 (d, J=1.8 Hz, 1 H, H-6′), 7.494 (d, J=2.4 Hz, 1 H, H-2′), 7.044–6.997 (m, 2 H, H-5, H-5′), 6.859 (d, J=20.4 Hz, 1 H, H-3), 3.835 (s, 3 H, OCH3-2), 3.790 (s, 3 H, OCH3-4); 13C NMR (DMSO-d6) δ 187.31, 162.70, 159.73, 150.50, 145.36, 137.27, 130.01, 129.95, 121.62, 119.35, 116.19, 115.30, 115.07, 106.23, 98.35, 55.78, 55.48. HR-MS m/z 301.1068 [M + H]+, Calcd. for C17H16O5: 300.0998.

(E)-1-(3,4-Dihydroxyphenyl)-3-(2-methoxyphenyl)prop-2-en-1-one (29): Red-brown power, 50.8% yield, m.p. 143.2–147.9 °C. 1H NMR (CDCl3) δ 8.107 (d, J=16.2 Hz, 1 H, H-β), 7.635 (d, J=16.2 Hz, 1 H, H-α), 7.773 (s, 1 H, H-2′), 7.591–7.635 (m, 2 H, H-5′, H-6′), 7.381 (t, J=7.8 Hz, 1 H, H-4), 6.937–7.008 (m, 3 H, H-3, H-5, H-6′), 3.924 (s, 3 H, OCH3-2); 13C NMR (DMSO-d6) δ 187.38, 158.10, 150.81, 145.46, 137.06, 131.80, 129.72, 128.40, 123.22, 122.09, 121.91, 120.67, 115.33, 115.12, 111.74, 55.67. HR-MS m/z 271.0995 [M + H] +, Calcd. for C16H14O4: 270.0892.

(E)-1-(3,4-Dimethoxyphenyl)-3-(2-methoxyphenyl)prop-2-en-1-one (30): Yellow powder, 58.9% yield, m.p. 53.9–55.0 °C. 1H NMR (DMSO-d6) δ 8.035 (d, J=15.6 Hz, 1 H, H-β), 7.989 (dd, J=1.8 Hz, J=1.8 Hz, 1 H, H-6′), 7.913–7.866 (m, 2 H, H-2′, H-6), 7.599 (d, J=2.4 Hz, 1 H, H-3), 7.468-7.440 (m, 1 H, H-4), 7.118 (t, J=15.6 Hz, 2 H, H-5, H-5′), 7.044 (t, J=15.0 Hz, 1 H, H-α), 3.907 (s, 3 H, OCH3-3′), 3.879 (s, 3 H, OCH3-4′), 3.866 (s, 3 H, OCH3-2); 13C NMR (DMSO-d6) δ 187.52, 158.16, 153.14, 148.85, 137.63, 131.84, 130.74, 128.32, 123.24, 123.08, 121.75, 120.56, 111.55, 110.75, 55.48 (3). HR-MS m/z 299.1212 [M + H]+, Calcd. for C18H18O4: 298.1205.

(E)-1-(3,4-Dihydroxyphenyl)-3-(2,3-dimethoxyphenyl)prop-2-en-1-one (31): Brown yellow powder, 20.0% yield, m.p. 160.2–163.2 °C. 1H NMR (DMSO-d6) δ 9.960 (s, 1 H, OH-3′), 9.407 (s, 1 H, OH-4′), 7.905 (d, J=15.6 Hz, 1 H, H-β), 7.813 (d, J=16.0 Hz, 1 H, H-α), 7.624 (d, J=8.0 Hz, 1 H, H-6′), 7.572 (s, 1 H, H-6), 7.521 (s, 1 H, H-5), 7.139(s, 2 H, H-2′, H-5′), 6.878 (d, J=8.0 Hz, 1 H, H-4), 3.845 (s, 3 H, OCH3-2), 3.798 (s, 3 H, OCH3-3); 13C NMR (DMSO-d6) δ 187.30, 152.77, 150.91, 148.10, 145.49, 136.50, 129.52, 128.44, 124.25, 123.10, 122.03, 119.15, 115.36, 115.12, 114.76, 60.86, 55.81. HR-MS m/z 301.1068 [M + H]+, Calcd. for C17H16O5: 300.0998.

(E)-1-(3,4-Dihydroxyphenyl)-3-(2,5-dimethoxyphenyl)prop-2-en-1-one (33): Yellow powder, 56.8% yield, m.p. 95.4–97.9 °C. 1H NMR (DMSO-d6) δ 9.869 (s, 1 H, OH-3′), 9.320 (s, 1 H, OH-4′), 7.926 (d, J=19.2 Hz, 1 H, H-β), 7.803 (d, J=19.2 Hz, 1 H, H-α), 7.615 (d, J=9.6 Hz, 1 H, H-6′), 7.495 (d, J=19.2 Hz, 2 H, H-2′, H-5′), 7.029 (d, J=8.4 Hz, 2 H, H-3, H-6), 6.872 (d, J=9.0 Hz, 1 H, H-4), 3.845 (s, 3 H, OCH3-2), 3.799 (s, 3 H, OCH3-5); 13C NMR (DMSO-d6) δ 187.36, 153.26, 152.56, 150.84, 145.45, 136.79, 129.70, 123.79, 122.28, 122.04, 117.63, 115.38, 115.07, 113.04, 112.62, 56.15, 55.67. HR-MS m/z 301.1068 [M + H]+, Calcd. for C17H16O5: 300.0998.

(E)-3-(2,5-Dimethoxyphenyl)-1-(3,4-dimethoxyphenyl)prop-2-en-1-one (34): Yellow powder, 74.3% yield, m.p. 72.5–73.4 °C. 1H NMR (CDCl3) δ 8.066 (d, J=15.5 Hz, 1 H, H-β), 7.680 (d, J=8.0 Hz, 1 H, H-6′), 7.607 (d, J=18.0 Hz, 2 H, H-2′, H-α), 7.178 (s, 1 H, H-6), 6.938 (d, J=7.5 Hz, 2 H, H-3, H-4), 6.884 (d, J=8.5 Hz, 1 H, H-5′), 3.974 (s, 6 H, OCH3-3′, OCH3-4′), 3.878 (s, 3 H, OCH3-2), 3.826 (s, 3 H, OCH3-5); 13C NMR (CDCl3) δ 189.25, 153.59, 153.30, 153.14, 149.22, 139.33, 131.61, 124.86, 123.00 (2), 116.86, 113.97, 112.53, 111.03, 110.06, 56.16, 56.07, 56.05, 55.87. HR-MS m/z 329.1389 [M + H]+, Calcd. for C19H20O5: 328.1311.

(E)-3-(4-Chlorophenyl)-1-(3,4-dihydroxyphenyl)prop-2-en-1-one (35): Light powder, 34.8% yield, m.p. 216.4–217.8 °C. 1H NMR (DMSO-d6) δ 9.980 (s, 1 H, OH-3′), 9.386 (s, 1 H, OH-4′), 7.906 (s, 1 H, H-β), 7.886 (t, J=15.0 Hz, 2 H, H-6, H-2), 7.666-7.623 (m, 2 H, H-2′, H-6′), 7.523 (d, J=2.4 Hz, 2 H, H-3, H-5), 7.507 (s, 1 H, H-α), 6.869 (d, J=8.4 Hz, 1 H, H-5′); 13C NMR (DMSO-d6) δ 188.55, 161.02, 159.02, 149.13, 145.70, 133.73, 130.30, 127.32, 125.71, 124.75, 122.54, 122.09, 116.58, 115.87, 114.97. HR-MS m/z 275.0502 [M + H]+, Calcd. for C15H11ClO3: 274.0397.

(E)-3-(3,4-Dichlorophenyl)-1-(3,4-dihydroxyphenyl)prop-2-en-1-one (37): Dark purple syrupy, 49.2% yield. 1H-NMR (DMSO-d6) δ 9.808 (s, 1 H, OH-3′), 9.122 (s, 1 H, OH-4′), 8.196 (t, J=9.0 Hz, 1 H, H-β), 8.025 (s, 1 H, H-2′), 7.643-7.591 (m, 3 H, H-α, H-6′, H-6), 7.305 (s, 1 H, H-2), 7.218 (d, J=9.5 Hz, 1 H, H-5′), 6.956 (d, J=8.0 Hz, 1 H, H-5). 13C NMR (DMSO-d6) δ 186.94, 151.16, 145.53, 139.55, 135.85, 132.29, 131.76, 130.88, 129.91, 129.39, 128.82, 124.36, 122.43, 115.46, 115.04. HR-MS m/z 308.9991 [M + H]+, Calcd. for C15H10Cl2O3: 308.0007.

(E)-1-(3,4-Dihydroxyphenyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one (39): Yellow powder, 56.4% yield, m.p. 118.9–121.0 °C. 1H NMR (CDCl3) δ 9.944 (s, 1 H, OH-3′), 9.370 (s, 1 H, OH-4′), 7.814 (d, J=12.0 Hz, 1 H, H-β), 7.671 (dd, J=2.4 Hz, J=2.4 Hz, 1 H, H-6′), 7.609 (d, J=15.0 Hz, 1 H, H-α), 7.533 (d, J=2.4 Hz, 1 H, H-2′), 7.195 (s, 2 H, H-2, H-6), 6.882 (d, J=7.8 Hz, 1 H, H-5′), 3.865 (s, 6 H, OCH3-3, OCH3-5), 3.712 (s, 3 H, OCH3-4); 13C NMR (DMSO-d6) δ 187.21, 153.09 (2), 150.82, 145.45, 142.85, 139.51, 130.48, 129.72, 122.13, 121.43, 115.43, 115.00, 106.30 (2), 60.10, 56.11 (2). HR-MS m/z 353.0999 [M + Na]+, Calcd. for C18H18O6: 330.1103.

(E)-1-(3,4-Dihydroxyphenyl)-3-(3,4-dimethoxyphenyl)prop-2-en-1-one (41): Yellow power, 64.3% yield, m.p. 109.5–111.0 °C. 1H NMR (CDCl3) δ 7.737 (d, J=15.6 Hz, 1 H, H-β), 7.648 (dd, J=1.8 Hz, J=1.8 Hz, 1 H, H-6′), 7.608 (d, J=15.6 Hz, 1 H, H-α), 7.519 (d, J=1.8 Hz, 1 H, H-2′), 7.508 (d, J=1.8 Hz, 1 H, H-2), 7.337 (dd, J=1.8 Hz, J=1.8 Hz, 1 H, H-6), 7.015 (d, J=8.4 Hz, 1 H, H-5′), 6.867 (d, J=8.4 Hz, 1 H, H-5), 3.863 (s, 3 H, OCH3-3), 3.817 (s, 3 H, OCH3-4); 13C NMR (DMSO-d6) δ 187.36, 153.26, 152.56, 150.84, 145.45, 136.79, 129.70, 123.79, 122.28, 122.04, 117.63, 115.38, 115.07, 113.04, 112.62, 56.15, 55.67. HR-MS m/z 301.1068 [M + H]+, Calcd. for C17H16O5: 300.0998.

5.2. Pharmacology

5.2.1. DPPH assay

The DPPH assay measured hydrogen atom (or one electron) donating activity and hence provided an evaluation of antioxidant activity due to free radical scavenging90. The test was prepared as described previously44., 91..

5.2.2. Cell culture

PC12 cells, rat pheochromocytoma cell lines, were obtained from the Cell Storage Center of Wuhan University (Wuhan, China). Cells were grown in 1× DMEM supplemented with 10% fetal bovine serum (FBS), containing 100 U/mL penicillin and 100 U/mL streptomycin, and incubated at 37 °C with 5% CO2.

5.2.3. MTT assay

3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide, thiazolyl blue (MTT) assay was used to measure cell viability. Briefly, cells were seeded in 96-well plates and cultured for 24 h. After appropriate treatments, the cells were incubated with 20 μL MTT (0.5 mg/mL). Following incubation at 37 °C for 4 h, media were aspirated from each well and DMSO (120 μL) was added. The absorbance was measured at λ=490 nm using a Microplate Reader (Bio-Rad, USA). Assays were repeated at least three times.

5.2.4. Lipid peroxidation assay

Levels of Malondialdehyde (MDA) were determined using the assay kit (Nanjing Jiancheng Bioengineering Institute, Nanjing, China) according to the manufacturer׳s instruction. At the end of the drug treatment, supernatants in the cells were collected through centrifugation. Supernatants were mixed with TBA (0.37%) solution and then boiled for 15 min at 100 °C. The samples were rapidly cooled to room temperature, and were determined with a microplate reader at a wavelength of 532 nm.

5.2.5. Detection of reactive oxygen species

Intracellular ROS generation was assessed with dichlorodihydrofluorescein diacetate (DCFH-DA, Beyotime Biotechnology, Shanghai, China). Cells were stained with 1 μL DCFH-DA (10 μmol/L) for 30 min at 37 °C in the dark. Cells were trypsinized, harvested, washed three times with PBS, resuspended in PBS and then analyzed by flow cytometry (Becton Dickinson, USA).

5.2.6. Immunofluorescence

PC12 cells were fixed with 4% paraformaldehyde for 20 min at room temperature and washed three times with PBS. The cells were permeabilized in 0.1% TritonX-100 (Sigma—Aldrich St. Louis, MO, USA) for 15 min and blocked in 1% BSA for 1 h at room temperature. After being washed, the cells were incubated with a 1:200 dilution of primary NRF2 antibody (sc-13032, Santa Cruz Biotechnology, USA, 1:200) at 4 °C overnight and incubated with appropriate secondary antibody (sc-13032, goat anti-rabbit IgG-PE, Santa Cruz Biotechnology, USA, 1:300) for 1 h at room temperature. Cell nuclei were stained with DAPI. The images were acquired with the fluorescence microscope (Nikon, Japan).

5.2.7. Real-time PCR analyses

After various treatments, the cells were collected and total RNA was extracted. Then, reverse transcription (RT) was performed with M-MLV Reverse Transcriptase (Thermo Fisher Scientific, MA, USA) as following: 65 °C for 5 min for the reverse transcription. And the real-time PCR assay was performed at 37 °C for 50 min and 70 °C for 15 min for the PCR reaction, with 40 cycles. Relative levels of mRNA were analysed by the following primers.

For mHO-1: 5′-GCCTGCTAGCCTGGTTCAAG-3′; 5′-AGCGGTGTCTGGGATGA ACTA-3′.

For mGCLC: 5′-GTCCTCAGGTGA CATTCCAAGC-3′; 5′-TGTTCTTCAGG GGCTCCAGTC-3′.

For mGAPDH: 5′-AAGCTGGTCATCA ACGGGAAAC-3′; 5′-GAAGACGCCAG TAGACTCCACG-3′.

Relative mRNA expression values were calculated by the—ΔΔCt method92.

5.2.8. Western blot analysis

PC12 cells were incubated in 6-well plates at a density of 3×105 and incubated for 24–48 h at 37 °C. After suitable treatments, the cells were collected and lysed with ice-cold RIPA lysis buffer. Equal amounts of protein samples (80 μg) were separated on a 10% SDS-PAGE gel and transferred electrophoretically onto nitrocellulose membrane. Subsequently, the membranes were blocked with 5% skim milk and incubated overnight at 4 °C with primary antibody: anti-HO-1 (sc-10789, Santa Cruz Biotechnology, 1:300), anti-GCLC (ab-80841, abcam Biotechnology, 1:600), anti-GADPH (sc-47724, Santa Cruz Biotechnology, 1:1000), anti-β-actin (AP0060, Bioworld Technology, 1:3000). After being washed three times with 1× TBST, the membrane was incubated with anti-rabbit IgG for 1 h at room temperature. Proteins were visualized by exposure in a ChemiDoc XRS+system (Bio-Rad, Hercules, CA, USA). Band density was quantified by Image J software (National Institute of Health, Bethesda, MD, USA).

5.2.9. Materials and animals

2,3,5-Triphenyltetrazolium (TTC) was purchased from Sigma (St. Louis, MO, USA). Chloral hydrate was purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). 33 and edaravone (ED) was dissolved in a solvent (Cremophor:PBS at 3:97) for the intraperitoneal injection. 33/21/1b-nanoparticles were prepared for the intracerebroventricular injection. The 33/21/1b-loaded nanoparticles were prepared as described previously93. All animals were obtained from the Shanghai Slaccas Lab Animal Co., Ltd. All animal experiments and care were performed according to the Guide for the Care and Use of Laboratory Animals (National Academy Press, Washington D.C., USA, 1996). Animals were fed with a standard laboratory diet, and were housed in a temperature-controlled room (24 °C) and illuminated for 12 h daily (lights on from 5 a.m. to 5 p.m.).

5.2.10. BCAO-induced cerebral ischemia/reperfusion injury in mice

This ischemia/reperfusion model was carried out as described by Himori et al.94 with slight modifications. Briefly, male 8-week-old C57BL/6 mice were anaesthetized using 4% of chloral hydrate (0.1 mL/10 g; i.p.). A midline incision was made in the neck and the left and right carotid arteries were exposed. A loose silk ligature for occlusion (ischemia) was placed around both carotid arteries. Occlusion was maintained for 20 min, and this was followed by reperfusion for 24 h. In sham-operated animals, the arteries were exposed but not occluded. All mice were injected intraperitoneally 3 or 6 h after bilateral common carotid artery occlusion (BCAO).

5.2.11. Spontaneous locomotor activity test

After 24 h of reperfusion, the animals were placed in an open square chamber (40 cm3 box) equipped with horizontal and vertical infrared photo beams. Then, its behaviors were recorded for 5 min using the Digbehv software (DigBehav, Jiliang Co., Ltd., Shanghai, China). The locomotor activity was evaluated by measuring the total distance traveled in the apparatus.

5.2.12. MCAO-induced transient focal cerebral ischemia in rats

Male Sprague—Dawley rats (250–280 g) were used in this study. Rats have no interference factors such as infection and inflammation, and were used as the object of middle cerebral artery occlusion (MCAO) method. Firstly, rats were anesthetized with 10% of chloral hydrate (0.33–0.35 mL/100 kg; i.p.), and then placed them in the supine position. Secondly, after disinfection with iodine, the skin was cut. The common carotid artery (CCA), external carotid artery (ECA) and internal carotid artery (ICA) were separated. Thirdly, the CCA and the ECA was ligated while the ICA was closed with an artery clamp temporarily. Then tiny incisions were made at the distance of 4 mm from the branch of CCA. The MCAO model was established by inserting thread through CCA into the anterior cerebral artery. The sham-operated group was treated with the same operation without ischemia-reperfusion.

5.2.13. Neurological deficit score and TTC staining

Neurological score was assessed 24 or 72 h after MCAO in rats. Five types of motor neurological findings are as follows. 0: no obvious deficit; 1: difficult to extend the lateral forelimb fully; 2: cannot extend the lateral forelimbs; 3: circling to the contralateral side; 4: difficult or impossible to move or roll spontaneously. TTC staining was performed to determine the infarct area. Firstly, the brain of the rat was taken out in time and placed in the refrigerator at –20 °C for 20 min. Secondly, the brain was cut into five slices with 2 mm thickness and placed in TTC staining (Sigma—Aldrich, USA) at 37 °C for 30 min. The TTC-stained brain slices were taken pictures with the camera, and then the Image-Pro plus was used to handle the infarct area.

5.2.14. Statistical analysis

Data were presented as means±SEM. The statistical differences between groups were determined by the Student׳s t-test or one-way analysis of variance for multiple comparisons in GraphPad Pro (GraphPad, San Diego, CA, USA). Differences were considered to be significant at P<0.05.

Acknowledgments

The work was supported by ZheJiang Province Natural Science Funding of China (Nos. LQ18H280008, Y19B020043, and LY17H160059, China), the National Natural Science Foundation of China (No. 81803580, China), University Students in Zhejiang Science and Technology Innovation Projects (No. 2018R413004, China), National Undergraduate Training Programs for Innovation and Entrepreneurship (No. 201810343025, China) and Granted by the Opening Project of Zhejiang Provincial Top Key Discipline of Pharmaceutical Sciences.

Footnotes

Peer review under responsibility of Institute of Materia Medica, Chinese Academy of Medical Sciences and Chinese Pharmaceutical Association.

Appendix A

Supplementary data associated with this article can be found in the online version at https://doi.org/10.1016/j.apsb.2019.01.003.

Contributor Information

Peihong Qiu, Email: wjzwzmc@126.com.

Jianzhang Wu, Email: wjzwzmu@163.com.

Appendix A. Supplementary material

Supplementary material.

mmc1.pdf (3.6MB, pdf)

.

References

  • 1.Flynn R.W., MacWalter R.S., Doney A.S. The cost of cerebral ischaemia. Neuropharmacology. 2008;55:250–256. doi: 10.1016/j.neuropharm.2008.05.031. [DOI] [PubMed] [Google Scholar]
  • 2.Durai Pandian J., Padma V., Vijaya P., Sylaja P.N., Murthy J.M. Stroke and thrombolysis in developing countries. Int J Stroke. 2007;2:17–26. doi: 10.1111/j.1747-4949.2007.00089.x. [DOI] [PubMed] [Google Scholar]
  • 3.Uchino K. Presenting to primary stroke centers or comprehensive stroke centers for thrombolysis. JAMA Neurol. 2017;74:1269. doi: 10.1001/jamaneurol.2017.2015. [DOI] [PubMed] [Google Scholar]
  • 4.Wu J., Ling J., Wang X., Li T., Liu J., Lai Y. Discovery of a potential anti-ischemic stroke agent: 3-pentylbenzo[c]thiophen-1(3H)-one. J Med Chem. 2012;55:7173–7181. doi: 10.1021/jm300681r. [DOI] [PubMed] [Google Scholar]
  • 5.Candelario-Jalil E. Injury and repair mechanisms in ischemic stroke: considerations for the development of novel neurotherapeutics. Curr Opin Investig Drugs. 2009;10:644–654. [PubMed] [Google Scholar]
  • 6.Yen T.L., Hsu C.K., Lu W.J., Hsieh C.Y., Hsiao G., Chou D.S. Neuroprotective effects of xanthohumol, a prenylated flavonoid from hops (Humuluslupulus), in ischemic stroke of rats. J Agric Food Chem. 2012;60:1937–1944. doi: 10.1021/jf204909p. [DOI] [PubMed] [Google Scholar]
  • 7.Eltzschig H.K., Eckle T. Ischemia and reperfusion—from mechanism to translation. Nat Med. 2011;17:1391–1401. doi: 10.1038/nm.2507. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Pantazi E., Bejaoui M., Folch-Puy E., Adam R., Roselló-Catafau J. Advances in treatment strategies for ischemia reperfusion injury. Expert Opin Pharmacother. 2016;17:169–179. doi: 10.1517/14656566.2016.1115015. [DOI] [PubMed] [Google Scholar]
  • 9.Trippier P.C., Jansen Labby K., Hawker D.D., Mataka J.J., Silverman R.B. Target- and mechanism-based therapeutics for neurodegenerative diseases: strength in numbers. J Med Chem. 2013;56:3121–3147. doi: 10.1021/jm3015926. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Pérez-González A., Galano A. OH radical scavenging activity of Edaravone: mechanism and kinetics. J Phys Chem B. 2011;115:1306–1314. doi: 10.1021/jp110400t. [DOI] [PubMed] [Google Scholar]
  • 11.Dinkova-Kostova A.T., Talalay P. Direct and indirect antioxidant properties of inducers of cytoprotective proteins. Mol Nutr Food Res. 2008;52:S128–S138. doi: 10.1002/mnfr.200700195. [DOI] [PubMed] [Google Scholar]
  • 12.Jung K.A., Kwak M.K. The NRF2 system as a potential target for the development of indirect antioxidants. Molecules. 2010;15:7266–7291. doi: 10.3390/molecules15107266. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13.Magesh S., Chen Y., Hu L. Small molecule modulators of KEAP1-NRF2-ARE pathway as potential preventive and therapeutic agents. Med Res Rev. 2012;32:687–726. doi: 10.1002/med.21257. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14.Guo Z. The modification of natural products for medical use. Acta Pharm Sin B. 2017;7:119–136. doi: 10.1016/j.apsb.2016.06.003. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 15.Rigano D., Sirignano C., Taglialatela-Scafati O. The potential of natural products for targeting PPARα. Acta Pharm Sin B. 2017;7:427–438. doi: 10.1016/j.apsb.2017.05.005. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 16.Wu JZ., Xi YY., Huang LL., Li G., Mao QQ., Fang CY. A steroid-type antioxidant targeting the KEAP1/NRF2/ARE signaling pathway from the soft coral Dendronephthya gigantea. J Nat Prod. 2018;81:2567–2575. doi: 10.1021/acs.jnatprod.8b00728. [DOI] [PubMed] [Google Scholar]
  • 17.Dimmock J.R., Elias D.W., Beazely M.A., Kandepu N.M. Bioactivities of chalcones. Curr Med Chem. 1999;6:1125–1149. [PubMed] [Google Scholar]
  • 18.Niu H., Wang W., Li J., Lei Y., Zhao Y., Yang W. A novel structural class of coumarin-chalcone fibrates as PPARα/γ agonists with potent antioxidant activities: design, synthesis, biological evaluation and molecular docking studies. Eur J Med Chem. 2017;138:212–220. doi: 10.1016/j.ejmech.2017.06.033. [DOI] [PubMed] [Google Scholar]
  • 19.Cheng J.H., Hung C.F., Yang S.C., Wang J.P., Won S.J., Lin C.N. Synthesis and cytotoxic, anti-inflammatory, and anti-oxidant activities of 2′,5′-dialkoxylchalcones as cancer chemopreventive agents. Bioorg Med Chem. 2008;16:7270–7276. doi: 10.1016/j.bmc.2008.06.031. [DOI] [PubMed] [Google Scholar]
  • 20.El Sayed Aly M.R., Abd El Razek Fodah H.H., Saleh S.Y. Antiobesity, antioxidant and cytotoxicity activities of newly synthesized chalcone derivatives and their metal complexes. Eur J Med Chem. 2014;76:517–530. doi: 10.1016/j.ejmech.2014.02.021. [DOI] [PubMed] [Google Scholar]
  • 21.Wu JZ., Wang C., Cai YP., Peng J., Liang DL., Zhao YJ. Synthesis and crystal structure of chalcones as well as on cytotoxicity and antibacterial properties. Med Chem Res. 2012;21:444–452. [Google Scholar]
  • 22.Lorenzo P., Alvarez R., Ortiz M.A., Alvarez S., Piedrafita F.J., De Lera Á.R. Inhibition of IκB kinase-β and anticancer activities of novel chalcone adamantyl arotinoids. J Med Chem. 2008;51:5431–5440. doi: 10.1021/jm800285f. [DOI] [PubMed] [Google Scholar]
  • 23.Zhu M., Wang JB., Xie JW., Chen LP., Wei XY., Jiang X. Design, synthesis, and evaluation of chalcone analogues incorporate α,β-unsaturated ketone functionality as anti-lung cancer agents via evoking ROS to induce pyroptosis. Eur J Med Chem. 2018;157:1395–1405. doi: 10.1016/j.ejmech.2018.08.072. [DOI] [PubMed] [Google Scholar]
  • 24.Tuncel S., Fournier-dit-Chabert J., Albrieux F., Ahsen V., Ducki S., Dumoulin F. Towards dual photodynamic and antiangiogenic agents: design and synthesis of a phthalocyanine-chalcone conjugate. Org Biomol Chem. 2012;10:1154–1157. doi: 10.1039/c2ob06809e. [DOI] [PubMed] [Google Scholar]
  • 25.Zhang YL., Wu JZ., Ying SL., Chen GZ., Wu BB., Xu TT. Discovery of new MD2 inhibitor from chalcone derivatives with anti-inflammatory effects in LPS-induced acute lung injury. Sci Rep. 2016;6:25130–25142. doi: 10.1038/srep25130. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Wu J., Li J., Cai Y., Pan Y., Ye F., Zhang Y. Evaluation and discovery of novel synthetic chalcone derivatives as anti-inflammatory agents. J Med Chem. 2011;54:8110–8123. doi: 10.1021/jm200946h. [DOI] [PubMed] [Google Scholar]
  • 27.Menezes J.C., Kamat S.P., Cavaleiro J.A., Gaspar A., Garrido J., Borges F. Synthesis and antioxidant activity of long chain alkyl hydroxycinnamates. Eur J Med Chem. 2011;46:773–777. doi: 10.1016/j.ejmech.2010.12.016. [DOI] [PubMed] [Google Scholar]
  • 28.Gaspar A., Martins M., Silva P., Garrido E.M., Garrido J., Firuzi O. Dietary phenolic acids and derivatives. Evaluation of the antioxidant activity of sinapic acid and its alkyl esters. J Agric Food Chem. 2010;58:11273–11280. doi: 10.1021/jf103075r. [DOI] [PubMed] [Google Scholar]
  • 29.Cos P., Rajan P., Vedernikova I., Calomme M., Pieters L., Vlietinck A.J. In vitro antioxidant profile of phenolic acid derivatives. Free Radic Res. 2002;36:711–716. doi: 10.1080/10715760290029182. [DOI] [PubMed] [Google Scholar]
  • 30.Teixeira J., Cagide F., Benfeito S., Soares P., Garrido J., Baldeiras I. Development of a mitochondriotropic antioxidant based on caffeic acid: proof of concept on cellular and mitochondrial oxidative stress models. J Med Chem. 2017;60:7084–7098. doi: 10.1021/acs.jmedchem.7b00741. [DOI] [PubMed] [Google Scholar]
  • 31.Kumar V., Kumar S., Hassan M., Wu H., Thimmulappa R.K., Kumar A. Novel chalcone derivatives as potent NRF2 activators in mice and human lung epithelial cells. J Med Chem. 2011;54:4147–4159. doi: 10.1021/jm2002348. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32.Kozlowski D., Trouillas P., Calliste C., Marsal P., Lazzaroni R., Duroux J.L. Density functional theory study of the conformational, electronic, and antioxidant properties of natural chalcones. J Phys Chem A. 2007;111:1138–1145. doi: 10.1021/jp066496+. [DOI] [PubMed] [Google Scholar]
  • 33.Rao Y.K., Fang S.H., Tzeng Y.M. Synthesis and biological evaluation of 3′,4′,5′-trimethoxychalcone analogues as inhibitors of nitric oxide production and tumor cell proliferation. Bioorg Med Chem. 2009;17:7909–7914. doi: 10.1016/j.bmc.2009.10.022. [DOI] [PubMed] [Google Scholar]
  • 34.Meng C.Q., Ni L., Worsencroft K.J., Ye Z., Weingarten M.D., Simpson J.E. Carboxylated, heteroaryl-substituted chalcones as inhibitors of vascular cell adhesion molecule-1 expression for use in chronic inflammatory diseases. J Med Chem. 2007;50:1304–1315. doi: 10.1021/jm0614230. [DOI] [PubMed] [Google Scholar]
  • 35.Bandgar B.P., Patil S.A., Korbad B.L., Nile S.H., Khobragade C.N. Synthesis and biological evaluation of β-chloro vinyl chalcones as inhibitors of TNF-α and IL-6 with antimicrobial activity. Eur J Med Chem. 2010;45:2629–2633. doi: 10.1016/j.ejmech.2010.01.050. [DOI] [PubMed] [Google Scholar]
  • 36.Ning X., Guo Y., Wang X., Ma X., Tian C., Shi X. Design, synthesis, and biological evaluation of (E)-3,4-dihydroxystyryl aralkyl sulfones and sulfoxides as novel multifunctional neuroprotective agents. J Med Chem. 2014;57:4302–4312. doi: 10.1021/jm500258v. [DOI] [PubMed] [Google Scholar]
  • 37.Talalay P., Dinkova-Kostova A.T., Holtzclaw W.D. Importance of phase 2 gene regulation in protection against electrophile and reactive oxygen toxicity and carcinogenesis. Adv EnzymeRegul. 2003;43:121–134. doi: 10.1016/s0065-2571(02)00038-9. [DOI] [PubMed] [Google Scholar]
  • 38.Yao J., Zhang B., Ge C., Peng S., Fang J. Xanthohumol, a polyphenol chalcone present in hops, activating NRF2 enzymes to confer protection against oxidative damage in PC12 cells. J Agric Food Chem. 2015;63:1521–1531. doi: 10.1021/jf505075n. [DOI] [PubMed] [Google Scholar]
  • 39.Peng S., Zhang B., Meng X., Yao J., Fang J. Synthesis of piperlongumine analogues and discovery of nuclear factor erythroid 2-related factor 2 (NRF2) activators as potential neuroprotective agents. J Med Chem. 2015;58:5242–5255. doi: 10.1021/acs.jmedchem.5b00410. [DOI] [PubMed] [Google Scholar]
  • 40.Peng S., Hou Y., Yao J., Fang J. Activation of NRF2-driven antioxidant enzymes by cardamonin confers neuroprotection of PC12 cells against oxidative damage. Food Funct. 2017;8:997–1007. doi: 10.1039/c7fo00054e. [DOI] [PubMed] [Google Scholar]
  • 41.Olatunji O.J., Chen H., Zhou Y. Neuroprotective effect of trans-N-caffeoyltyramine from Lycium chinese against H2O2 induced cytotoxicity in PC12 cells by attenuating oxidative stress. Biomed Pharmacother. 2017;93:895–902. doi: 10.1016/j.biopha.2017.07.013. [DOI] [PubMed] [Google Scholar]
  • 42.Cao G.S., Li S.X., Wang Y., Xu Y.Q., Lv Y.N., Kou J.P. A combination of four effective components derived from Sheng-mai san attenuates hydrogen peroxide-induced injury in PC12 cells through inhibiting Akt and MAPK signaling pathways. Chin J Nat Med. 2016;14:508–517. doi: 10.1016/S1875-5364(16)30060-7. [DOI] [PubMed] [Google Scholar]
  • 43.Wu J.Z., Cheng C.C., Shen L.L., Wang Z.K., Wu S.B., Li W.L. Synthetic chalcones with potent antioxidant ability on H2O2-induced apoptosis in PC12 cells. Int J Mol Sci. 2014;15:18525–18539. doi: 10.3390/ijms151018525. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 44.Huang L., Wang J., Chen L., Zhu M., Wu S., Chu S. Design, synthesis, and evaluation of NDGA analogues as potential anti-ischemic stroke agents. Eur J Med Chem. 2018;143:1165–1173. doi: 10.1016/j.ejmech.2017.09.028. [DOI] [PubMed] [Google Scholar]
  • 45.Jiao Z.Z., Yue S., Sun H.X., Jin T.Y., Wang H.N., Zhu R.X. Indoline amide glucosides from Portulaca oleracea: isolation, structure, and DPPH radical scavenging activity. J Nat Prod. 2015;78:2588–2597. doi: 10.1021/acs.jnatprod.5b00524. [DOI] [PubMed] [Google Scholar]
  • 46.Chen J., Zeng L., Xia T., Li S., Yan T., Wu S. Toward a biomarker of oxidative stress: a fluorescent probe for exogenous and endogenous malondialdehyde in living cells. Anal Chem. 2015;87:8052–8056. doi: 10.1021/acs.analchem.5b02032. [DOI] [PubMed] [Google Scholar]
  • 47.Wu J., Ren J., Yao S., Wang J., Huang L., Zhou P. Novel antioxidants׳ synthesis and their anti-oxidative activity through activating NRF2 signaling pathway. Bioorg Med Chem Lett. 2017;27:1616–1619. doi: 10.1016/j.bmcl.2017.02.006. [DOI] [PubMed] [Google Scholar]
  • 48.Wang X., Wang L., Li T., Huang Z., Lai Y., Ji H. Novel hybrids of optically active ring-opened 3-n-butylphthalide derivative and isosorbide as potential anti-ischemic stroke agents. J Med Chem. 2013;56:3078–3089. doi: 10.1021/jm4001693. [DOI] [PubMed] [Google Scholar]
  • 49.Liu Y., Ai K., Ji X., Askhatova D., Du R., Lu L. Comprehensive insights into the multi-antioxidative mechanisms of melanin nanoparticles and their application to protect brain from injury in ischemic stroke. J Am Chem Soc. 2017;139:856–862. doi: 10.1021/jacs.6b11013. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 50.The IST-3 Collaborative Group The benefits and harms of intravenous thrombolysis with recombinant tissue plasminogen activator within 6 h of acute ischaemic stroke (the third international stroke trial [IST-3]): a randomised controlled trial. Lancet. 2012;379:2352–2363. doi: 10.1016/S0140-6736(12)60768-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 51.Evenson K.R., Rosamond W.D., Morris D.L. Prehospital and in-hospital delays in acute stroke care. Neuroepidemiology. 2001;20:65–76. doi: 10.1159/000054763. [DOI] [PubMed] [Google Scholar]
  • 52.Chang C., Zhao Y., Song G., She K. Resveratrol protects hippocampal neurons against cerebral ischemia-reperfusion injury via modulating JAK/ERK/STAT signaling pathway in rats. J Neuroimmunol. 2018;315:9–14. doi: 10.1016/j.jneuroim.2017.11.015. [DOI] [PubMed] [Google Scholar]
  • 53.Farías J.G., Molina V.M., Carrasco R.A., Zepeda A.B., Figueroa E., Letelier P. Antioxidant therapeutic strategies for cardiovascular conditions associated with oxidative stress. Nutrients. 2017;9:966–988. doi: 10.3390/nu9090966. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 54.Patel R.P., Lang J.D., Smith A.B., Crawford J.H. Redox therapeutics in hepatic ischemia reperfusion injury. World J Hepatol. 2014;6:1–8. doi: 10.4254/wjh.v6.i1.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 55.Margaill I., Plotkine M., Lerouet D. Antioxidant strategies in the treatment of stroke. Free Radic Biol Med. 2005;39:429–443. doi: 10.1016/j.freeradbiomed.2005.05.003. [DOI] [PubMed] [Google Scholar]
  • 56.Dennis J.M., Witting P.K. Protective role for antioxidants in acute kidney disease. Nutrients. 2017;9:718. doi: 10.3390/nu9070718. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 57.Panizo N., Rubio-Navarro A., Amaro-Villalobos J.M., Egido J., Moreno J.A. Molecular mechanisms and novel therapeutic approaches to rhabdomyolysis-induced acute kidney injury. Kidney Blood Press Res. 2015;40:520–532. doi: 10.1159/000368528. [DOI] [PubMed] [Google Scholar]
  • 58.Carroll J.E., Howard E.F., Hess D.C., Wakade C.G., Chen Q., Cheng C. Nuclear factor-κB activation during cerebral reperfusion: effect of attenuation with N-acetylcysteine treatment. Mol Brain Res. 1998;56:186–191. doi: 10.1016/s0169-328x(98)00045-x. [DOI] [PubMed] [Google Scholar]
  • 59.Shah Z.A., Li R.C., Thimmulappa R.K., Kensler T.W., Yamamoto M., Biswal S. Role of reactive oxygen species in modulation of NRF2 following ischemic reperfusion injury. Neuroscience. 2007;147:53–59. doi: 10.1016/j.neuroscience.2007.02.066. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 60.Shih A.Y., Li P., Murphy T.H. A small-molecule-inducible NRF2-mediated antioxidant response provides effective prophylaxis against cerebral ischemia in vivo. J Neurosci. 2005;25:10321–10335. doi: 10.1523/JNEUROSCI.4014-05.2005. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 61.Sun J., Ren X., Simpkins J.W. Sequential upregulation of superoxide dismutase 2 and heme oxygenase 1 by tert-butylhydroquinone protects mitochondria during oxidative stress. Mol Pharm. 2015;88:437–449. doi: 10.1124/mol.115.098269. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 62.Joko S., Watanabe M., Fuda H., Takeda S., Furukawa T., Hui S.P. Comparison of chemical structures and cytoprotection abilities between direct and indirect antioxidants. J Funct Foods. 2017;35:245–255. [Google Scholar]
  • 63.Manev H., Uz T., Kharlamov A., Joo J.Y. Increased brain damage after stroke or excitotoxic seizures in melatonin-deficient rats. FASEB J. 1996;10:1546–1551. doi: 10.1096/fasebj.10.13.8940301. [DOI] [PubMed] [Google Scholar]
  • 64.Ren J., Fan C., Chen N., Huang J., Yang Q. Resveratrol pretreatment attenuates cerebral ischemic injury by upregulating expression of transcription factor NRF2 and HO-1 in rats. Neurochem Res. 2011;36:2352–2362. doi: 10.1007/s11064-011-0561-8. [DOI] [PubMed] [Google Scholar]
  • 65.Yang C., Zhang X., Fan H., Liu Y. Curcumin upregulates transcription factor NRF2, HO-1 expression and protects rat brains against focal ischemia. Brain Res. 2009;1282:133–141. doi: 10.1016/j.brainres.2009.05.009. [DOI] [PubMed] [Google Scholar]
  • 66.Jeon K.H., Lee E., Jun K.Y., Eom J.E., Kwak S.Y., Na Y. Neuroprotective effect of synthetic chalcone derivatives as competitive dual inhibitors against mu-calpain and cathepsin B through the downregulation of tau phosphorylation and insoluble Aβ peptide formation. Eur J Med Chem. 2016;121:433–444. doi: 10.1016/j.ejmech.2016.06.008. [DOI] [PubMed] [Google Scholar]
  • 67.Padmavathi G., Roy N.K., Bordoloi D., Arfuso F., Mishra S., Sethi G. Butein in health and disease: a comprehensive review. Phytomedicine. 2017;25:118–127. doi: 10.1016/j.phymed.2016.12.002. [DOI] [PubMed] [Google Scholar]
  • 68.Lee M.J., Lee H.S., Kim H., Yi H.S., Park S.D., Moon H.I. Antioxidant properties of benzylchroman derivatives from Caesalpinia sappan L. against oxidative stress evaluated in vitro. J Enzym Inhib Med Chem. 2010;25:608–614. doi: 10.3109/14756360903373376. [DOI] [PubMed] [Google Scholar]
  • 69.Wang W., Chen W., Yang Y.S., Liu T.X., Yang H.Y., Xin Z.H. New phenolic compounds from coreopsis tinctoria nutt. and their antioxidant and angiotensin I-converting enzyme inhibitory activities. J Agric Food Chem. 2015;63:200–207. doi: 10.1021/jf504289g. [DOI] [PubMed] [Google Scholar]
  • 70.Chiruta C., Schubert D., Dargusch R., Maher P. Chemical modification of the multitarget neuroprotective compound fisetin. J Med Chem. 2012;55:378–389. doi: 10.1021/jm2012563. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 71.Dziedzic S.Z., Hudson B.J.F. Polyhydroxy chalcones and flavanones as antioxidants for edible oils. Food Chem. 1983;12:205–212. [Google Scholar]
  • 72.Benayahoum A., Amira-Guebailia H., Houache O.A. DFT method for the study of the antioxidant action mechanism of resveratrol derivatives. J Mol Model. 2013;19:2285–2298. doi: 10.1007/s00894-013-1770-7. [DOI] [PubMed] [Google Scholar]
  • 73.Foti C., Piattelli M., Baratta M.T., Ruberto G. Flavonoids, coumarins, and cinnamic acids as antioxidants in a micellar system. Structure—activity relationship. J Agric Food Chem. 1996;44:497–501. [Google Scholar]
  • 74.Sogawa S., Nihro Y., Ueda H., Izumi A., Miki T., Matsumoto H. 3,4-Dihydroxychalcones as potent 5-lipoxygenase and cyclooxygenase inhibitors. J Med Chem. 1993;36:3904–3909. doi: 10.1021/jm00076a019. [DOI] [PubMed] [Google Scholar]
  • 75.Bodiwala H.S., Sabde S., Gupta P., Mukherjee R., Kumar R., Garg P. Design and synthesis of caffeoyl-anilides as portmanteau inhibitors of HIV-1 integrase and CCR5. Bioorg Med Chem. 2011;19:1256–1263. doi: 10.1016/j.bmc.2010.12.031. [DOI] [PubMed] [Google Scholar]
  • 76.Sharma N., Joshi Y.C. Synthesis of substituted chalcones under solvent-free microwave irradiation conditions and their antimicrobial evaluation. Int J Pharm Pharm Sci. 2012;4:436–439. [Google Scholar]
  • 77.Bai X.G., Xu C.L., Zhao S.S., He H.W., Wang Y.C., Wang J.X. Synthesis and cytotoxic evaluation of alkoxylated chalcones. Molecules. 2014;19:17256–17278. doi: 10.3390/molecules191117256. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 78.Wu JZ, Li WL, Chen LZ, Chu SH., Zhao CG., Wei TY. Synthesis, crystal structure, antioxidant activity of chalcones and its spiro-heterocyclic analogues. Chin J Org Chem. 2012;32:2141–2147. [Google Scholar]
  • 79.odorova I.T., Batovska D.I., Stamboliyska B.A. Evaluation of the radical scavenging activity of a series of synthetic hydroxychalcones towards the DPPH radical. J Serb Chem Soc. 2011;76:491–497. [Google Scholar]
  • 80.Raghavan S., Manogaran P., Venkatraman G. Synthesis and anticancer activity of chalcones derived from vanillin and isovanillin. Med Chem Res. 2015;24:1–9. [Google Scholar]
  • 81.Dahae L., Ki Hyun K., Sung Won M. Synthesis and biological evaluation of chalcone analogues as protective agents against cisplatin-induced cytotoxicity in kidney cells. Bioorg Med Chem Lett. 2015;25:1929–1932. doi: 10.1016/j.bmcl.2015.03.026. [DOI] [PubMed] [Google Scholar]
  • 82.Rao Y.K., Fang S.H., Tzeng Y.M. Synthesis and biological evaluation of 3′,4′,5′-trimethoxychalcone analogues as inhibitors of nitric oxide production and tumor cell proliferation. Bioorg Med Chem. 2009;17:7909–7914. doi: 10.1016/j.bmc.2009.10.022. [DOI] [PubMed] [Google Scholar]
  • 83.Bhat B.A., Dhar K.L., Puri S.C. Synthesis and biological evaluation of chalcones and their derived pyrazoles as potential cytotoxic agents. Bioorg Med Chem Lett. 2005;15:3177–3180. doi: 10.1016/j.bmcl.2005.03.121. [DOI] [PubMed] [Google Scholar]
  • 84.Lopez S.N., Castelli M.V., Zacchino S.A., Dominguez J.N., Lobo G., Charris-Charris J. In vitro antifungal evaluation and structure-activity relationships of a new series of chalcone derivatives and synthetic analogues, with inhibitory properties against polymers of the fungal cell wall. Bioorg Med Chem. 2001;9:1999–2013. doi: 10.1016/s0968-0896(01)00116-x. [DOI] [PubMed] [Google Scholar]
  • 85.Yamali C., Ozgun D.O., Gul H.I. Synthesis and structure elucidation of 1-(2,5/3,5-difluorophenyl)-3-(2,3/2,4/2,5/3,4-dimethoxyphenyl)-2-propen-1-ones as anticancer agents. Med Chem Res. 2017;26:1–9. [Google Scholar]
  • 86.Srinivasan B., Johnson T.E., Lad R., Xing C. Structure—activity relationship studies of chalcone leading to 3-hydroxy-4,3′,4′,5′-tetramethoxychalcone and its analogues as potent nuclear factor κB inhibitors and their anticancer activities. J Med Chem. 2009;52:7228–7235. doi: 10.1021/jm901278z. [DOI] [PubMed] [Google Scholar]
  • 87.Ivanova A.B., Batovska D.I., Todorova I.T., Stamboliyska B.A., Serly J., Molnar J. Comparative study on the MDR reversal effects of selected chalcones. Int J Med Chem. 2011;2011:530780–530787. doi: 10.1155/2011/530780. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 88.Gu X.H., Yu H., Jacobson A.E., Rothman R.B., Dersch C.M., George C. Design, synthesis, and monoamine transporter binding site affinities of methoxy derivatives of indatraline. J Med Chem. 2000;43:4868–4876. doi: 10.1021/jm000329v. [DOI] [PubMed] [Google Scholar]
  • 89.Pathak V., Ahmad I., Kahlon A.K. Syntheses of 2-methoxyestradiol and eugenol template based diarylpropenes as non-steroidal anticancer agents. RSC Adv. 2014;4:35171–35185. [Google Scholar]
  • 90.Mikulski D., Górniak R., Molski M. A theoretical study of the structure-radical scavenging activity of trans-resveratrol analogues and cis-resveratrol in gas phase and water environment. Eur J Med Chem. 2010;45:1015–1027. doi: 10.1016/j.ejmech.2009.11.044. [DOI] [PubMed] [Google Scholar]
  • 91.Braca A., Sortino C., Politi M., Morelli I., Mendez J. Antioxidant activity of flavonoids from Licania licaniaeflora. J Ethnopharmacol. 2002;79:379–381. doi: 10.1016/s0378-8741(01)00413-5. [DOI] [PubMed] [Google Scholar]
  • 92.Schmittgen T.D., Livak K.J. Analyzing real-time PCR data by the comparative CT method. Nat Protoc. 2008;3:1101–1108. doi: 10.1038/nprot.2008.73. [DOI] [PubMed] [Google Scholar]
  • 93.Xu H.L., Mao K.L., Lu C.T., Fan Z.L., Yang J.J., Xu J. An injectable acellular matrix scaffold with absorbable permeable nanoparticles improves the therapeutic effects of docetaxel on glioblastoma. Biomaterials. 2016;107:44–60. doi: 10.1016/j.biomaterials.2016.08.026. [DOI] [PubMed] [Google Scholar]
  • 94.Himori N., Watanabe H., Akaike N., Kurasawa M., Itoh J., Tanaka Y. Cerebral ischemia model with conscious mice: involvement of NMDA receptor activation and derangement of learning and memory ability. J Pharmacol Methods. 1990;23:311–327. doi: 10.1016/0160-5402(90)90059-t. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplementary material.

mmc1.pdf (3.6MB, pdf)

Articles from Acta Pharmaceutica Sinica. B are provided here courtesy of Elsevier

RESOURCES