Abstract
Background: The dawn of the year 2020 witnessed the spread of the highly infectious and communicable disease coronavirus disease 2019 (COVID-19) globally since it was first reported in 2019. Severe acute respiratory syndrome coronavirus-2 is the main causative agent. In total, 3,096,626 cases and 217,896 deaths owing to COVID-19 were reported by 30th April, 2020 by the World Health Organization. This means infection and deaths show an exponential growth globally. In order to tackle this pandemic, it is necessary to find possible easily accessible therapeutic agents till an effective vaccine is developed.
Methods: In this study, we present the results of molecular docking processes through high throughput virtual screening to analyze drugs recommended for the treatment of COVID-19.
Results: Atovaquone, fexofenadine acetate (Allegra), ethamidindole, baicalin, glycyrrhetic acid, justicidin D, euphol, and curine are few of the lead molecules found after docking 129 known antivirals, antimalarial, antiparasitic drugs and 992 natural products.
Conclusions: These molecules could act as an effective inhibitory drug against COVID-19.
Keywords: COVID-19, SARS-CoV-2, Molecular Docking
Introduction
Coronavirus Disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), that is responsible for respiratory illness and probably many more is yet to be discovered. This novel virus was first identified on 30 th December, 2019, with its first infection case infecting a human, which was reported in Wuhan city located in Hubei, China 1. Coronaviruses are mainly zoonotic, and are present amongst birds and mammals, causing respiratory, neurological, hepatic and enteric diseases 2 as well as comprises of enveloped RNA. The World Health Organization (WHO) declared this disease as a pandemic on 11th March, 2020 and SARS-CoV-2 as the deadliest virus till date on earth claiming 217,896 deaths till 30 th April, 2020 3.
Then, it is necessary for the rapid development and approval of a vaccine, which is not yet available 4. Nevertheless, Chang et al., 5 have suggested that some drugs against same type of viruses approved by the US Food and Drug Administration (FDA) might offer promising results. Hydroxychloroquine is one such drug that is used worldwide whereas Remdesivir and Ivermectin have been reported to work against COVID-19 in silico by others.
The transmission of this coronavirus occurs due to the binding of the CoV spike protein to the angiotensin converting enzyme 2 (ACE2) receptor present on the cell surface of the human host. The ACE2 receptor is present in the respiratory organs, kidneys, gastrointestinal tract (at high levels in the esophagus, colon, and small intestine, but low in the stomach), and testes. Virulence of this novel virus is due to the presence of main protease responsible for virus replication along with many major functions 6. Therefore, we have employed the main protease structure 6m03 as the target protein to identify the best inhibitory drugs in silico for our study.
SARS-CoV-2 (negatively stained) when observed under the electron micrograph was found to be spherical in shape with some pleiomorphic characteristic. The epithelial sections of human airway when observed, viruses were found in membrane bound vesicles in cytoplasm along with inclusion bodies. The virions appear similar to solar corona due to 9- to 12-nm distinctive spikes and the virions are 60 to 140 nm in diameter. Thus, it was established due to these morphological characteristics that this virus belongs to the Coronaviridae family along with its genome having more than 85% identity with a bat SARS-like CoV (bat-SL-CoVZC45, MG772933.1) genome as previously assessed via genome sequencing 6. SARS-Cov-2 initially infects lower airways, binds to ACE2 receptor on cells activating immune cells, thus, inducing the secretion of inflammatory cytokines and chemokines in human pulmonary system 4. Most COVID-19 patients exhibit flu-like symptoms within a span of two weeks from the exposure to the virus whereas there have been a majority rise in the asymptomatic COVID-19 patients.
In this work, we have performed high throughput virtual screening since it is the fastest approach in finding the probable drug against the target. High-throughput virtual screening (HTVS) of two databases was carried out via PyRx (Python prescription) software, which uses dock, Vina and Autodock as the docking tool. Autodock itself uses MGLTools comprising of computer aided drug discovery (CADD) pipeline for high throughput virtual screening of large databases for probable hits as target drugs. HTVS enables docking of multiple ligands on a single protein. PyRx is a freely available HTVS software. Docking results are based on the identification of pose visually and quantitatively using a scoring algorithm. Docking calculates the free binding energy (∆G) between the ligands and the protein. The free binding energy, thus calculated, is fundamental to the formation of complex systems in biochemistry and molecular biology. Lower free binding energy corresponds to a more favorable ligand binding affinity between a receptor and a ligand 7.
Methods
Molecular docking
Molecular docking is a bioinformatics method that allows predicting the orientation of a molecule, when it is bounded to another molecule 8, 9. There are two main approaches for molecular docking. The first approach describes the protein and the ligand as complementary surfaces 10. The second approach simulates the docking process calculating the ligand protein interaction based on the free binding energy ∆G 11.
Molecule selection
Selection of database and the COVID-19 main protease structure In this study, we have docked the X-ray crystal structure of main COVID protease protein (PDB ID: 6M03, resolution: 2 Å) with 129 molecules obtained from DrugBank and 992 molecules from the Zinc Natural Product database. The list of 129 molecules are provided along with the link for Zinc natural database in the Extended data 12. These 129 molecules chosen were either antimalarial, antiparasitic, antibiotics, or antivirals, since hydroxychloroquine, remdesivir and ivermectin are antimalarial, antiviral and antiparasitic drugs, respectively. The Zinc Natural Product Database was chosen since most of the drugs are natural derivatives used against various diseases at present and it is a freely available database. Similarity search could not be undertaken since there is no known drug to function 100% against this novel disease at time of publication.
Processing of macromolecules and ligands
Docking requires processing of the macromolecules and the ligands 13, 14. Water molecules were removed, polar hydrogen bonds were inserted into the crystal structure of 6m03 and it was converted to PDBQT format using AutoDock version 4. The energy of all ligands were minimized and they were converted into PDBQT files using Open Babel version 2.2.3 in PyRX version 0.8 15.
Molecular docking process
The grid box was determined as center the coordinates X:12.2632, Y:12.3998, and Z:5.4737, while as dimension the coordinates X:29.9242, Y:64.1097, and Z:48.1126.
The docking was done using Vina version 2.0 in PyRX. After the run, the out files stored in the user folder where the path run was specified in the edit preference. These output files were stored in PDBQT files, each having nine poses. The autodock application file was launched which then showed the empty dashboard along with "File" on the left hand corner of the page. The out file models were loaded using the "read molecule" application from the selected out file folder. Different poses were analyzed in the AutoDock tool. The pose with the lowest binding energy in kcal/mol was selected for further analysis. The docked molecules were then further converted into PDB format in PyMol and their interaction was studied using the software Discovery Studio version 4.1. The interaction can also be studied with PyMol but a better quality picture is obtained via Discovery studio. Three known drugs (hydroxychloroquine, remdesivir and ivermectin) were first docked against the virus main protease to check their binding energy. The interaction of these three drugs with the COVID-19 main protease could later be utilised for getting the hits.
Results
Docking results for reference molecules
The free binding energy for drugs known to act against COVID-19, which are hydroxychloroquine, remdesivir, and ivermectin, were found to be -5.5 kcal/mol, -6.3 kcal/mol, and -8.7 kcal/mol respectively as indicated in Table 1, which describes: a) PubChem compound ID (CID), which is the compound identifier in the PubChem database from where the 3D mol files of 129 molecules were downloaded; b) common drug name; and c) the free binding energy obtained after docking.
These drugs are known to improve the condition to some extent and yet their functions against COVID-19 are under study 16– 19.
Table 1. Docking of known COVID-19 inhibitors.
| PubChem CID | Drug Name | Binding energy
kcal/mol |
|---|---|---|
| 6321424 | Ivermectin | -8.7 |
| 121304016 | Remdisivir | -6.3 |
| 3652 | Hydroxychloroquine | -5.5 |
Therefore, we used these three molecules as our reference drugs. The interaction of these drugs with the virus main protease can be seen in the Figure 1. We could observe the interaction of these reference molecules as hydroxychloroquine forms a hydrogen bond with Tyr237 residue of the 6M03 main protease with a distance of 2.10 Å. It also interacts with Leu272 and Leu287. Remdisivir forms six hydrogen bonds with Lys137, Thr199, and Tyr239 along with interacting with Leu272, Leu287, Tyr237, and Asn238 residues of the 6M03 main protease. Ivermectin interacts with Leu272, Tyr239, Leu286, Leu287, Gly275, Asn277, and Met276 residues of the 6M03 main protease.
Figure 1. Reference molecules hydroxychloroquine, remdisivir, and ivermectin in complex with the COVID-19 main protease 6M03.
Docking results for 129 additional molecules
Keeping the free binding energy of our reference molecules in mind, we shortlisted 77 molecules from the database of 129 molecules with a cut of -6 kcal/mol free binding energy. Eprinomectin, artefenomel, doramectin, betulinic acid, atovaquone, and tetrandrine showed the lowest binding energies, at -9 kcal/mol, -8.7 kcal/mol, -8.4 kcal/mol, -8.4 kcal/mol, -8.2 kcal/mol and -8 kcal/mol, respectively. Table 2 presents the details of the best performing 18 of the 77 molecules along with their CID. These molecules have been considered due to the lowest free binding energy between the ligand and protein. Furthermore, their interactions with the virus main protease 6m03 was studied. Artefenomel interacts with Pro108, Val202, Ile249, Pro293, and Phe294 residues of the 6M03 main protease. Eprinomectin forms a hydrogen bond (2.26 Å) with Lys5 residue of the 6M03 main protease and also interacts with Leu286, Leu287, and Asn277. Tetrandrine forms a hydrogen bond with Arg131 and also interacts with Leu272, Leu286 and Leu287. Betulinic acid forms a hydrogen bond with Arg137 with 2.66 Å distance and also interacts with Leu272, Leu286, Leu287, Tyr237, and Tyr239. Doramectin forms three hydrogen bonds with Thr199, Lys5, and Gly138 as well as interacts with Leu286 and Asp289. Atovoquone forms a hydrogen bond with the Thr199 residue of the 6M03 main protease with a distance of 2.48 Å and also interacts with Lys137, Leu272, Leu286, Leu287, and Tyr239. These interactions can be observed in Figure 2. Full results are available in the Extended data 12.
Figure 2. Interaction of COVID-19 main protease 6M03 with ligands eprinomectin, artefenomel, doramectin, betulinic, atovaquone, and tetrandrine.
Table 2. Docking of drugs for probable COVID-19 inhibition.
| PubChem CID | Drug Name | Binding Energy
kcal/mol |
|
|---|---|---|---|
| 1 | 6450531 | Eprinomectin | -9 |
| 2 | 24999143 | Artefenomel | -8.7 |
| 3 | 9832750 | Doramectin | -8.4 |
| 4 | 64971 | Betulinic acid | -8.4 |
| 5 | 74989 | Atovaquone | -8.2 |
| 6 | 73078 | Tetrandrine | -8 |
| 7 | 6918632 | Emodepside | -7.9 |
| 8 | 124081896 | Baloxavir marboxil | -7.9 |
| 9 | 122262 | Piperaquine | -7.9 |
| 10 | 35802 | Flubendazole | -7.8 |
| 11 | 6917864 | Artesunate | -7.6 |
| 12 | 40692 | Mefloquine | -7.6 |
| 13 | 4030 | Mebendazole | -7.6 |
| 14 | 21389 | Imidocarb | -7.6 |
| 15 | 9832912 | Moxidectin | -7.5 |
| 16 | 439530 | Puromycin | -7.5 |
| 17 | 6323491 | Radicicol | -7.4 |
| 18 | 54671203 | Doxycycline | -7.4 |
| 19 | 107771 | Pyronaridine | -7.4 |
| 20 | 11979956 | Hachimycin | -7.3 |
Docking Results for natural molecules
A total of 34 molecules of natural origin were chosen from the datasets of 992 molecules with a cut off -8.9 kcal/mol. Table 3 presents the details of the best 20 molecules along with their common name and ZINC ID sorted by ascending order of the free binding energy of the top 20 molecules from natural products database. The interaction of various molecules with the 6M03 main protease was studied. Allegra forms three hydrogen bonds with Thr111, Asn151, and Asp153 as well as interacts with Arg298, Val305, and Phe305 residues of 6M03 main protease. Baicalin forms four hydrogen bonds with Thr111, Thr292, Ile152, and Arg298 along with interacting with Asp153, Asn151, and Val303 residues of the main protease 6M03. Curine forms three hydrogen bonds with Arg131, Thr199, and Leu287 along with having interactions with Asp289, Leu286, and Tyr237 residues of 6m03 main protease. Etamidindole forms two hydrogen bonds with Thr111 and Asp295, it also interacts with Phe8, Phe294, Arg295, Arg298, and Pro252 residues of main protease 6M03. Glycyrrhetic acid forms a hydrogen bond with Lys137(2.24 Å) as well as interacts with Tyr237, Tyr239, Leu272, Leu286, and Leu287 residues of the main protease 6m03. Euphol interacts with Phe8, Val297, Arg298, and Val303 residues of the main protease. The interaction of few of the 20 molecules with the protein can be seen in Figure 3. Full results are available in the Extended data 12.
Table 3. Docking of natural compounds for probable COVID-19 inhibitory activity.
| ZINC Prefix: ZINC000 ID | Common name | Binding energy
kcal/mol |
|
|---|---|---|---|
| 1 | 085592428 | Furobinordentatin | -9.9 |
| 2 | 085592420 | Alstiphyllanine F | -9.8 |
| 3 | 004104836 | Taraxerone | -9.6 |
| 4 | 085593550 | Morusin | -9.6 |
| 5 | 085596349 | Fexofenadine acetate (Allegra) | -9.6 |
| 6 | 085648318 | RA VII compound | -9.4 |
| 7 | 253589870 | Neoruscogenin | -9.3 |
| 8 | 006627242 | Justicidin D / neojusticidin A | -9.3 |
| 9 | 005742262 | Licoricidin | -9.2 |
| 10 | 085643829 | Euphol | -9.2 |
| 11 | 085593537 | Schisandrene | -9.2 |
| 12 | 029483258 | Curine | -9.1 |
| 13 | 005808583 | Bikaverin | -9.1 |
| 14 | 014966151 | Angoluvarin | -9.1 |
| 15 | 013543704 | Baicalin | -9.1 |
| 16 | 085642858 | Glycyrrhetic acid | -9.1 |
| 17 | 004995171 | Isomitraphylline | -9 |
| 18 | 008829747 | Rutarensin | -8.9 |
| 19 | 034075173 | Jolkinol B | -8.9 |
| 20 | 003838672 | Ethamidindole | -8.9 |
Figure 3. Interaction of six of the top 20 hits from Zinc natural database with main protease 6m03.
Discussion
HTVS is one of the best methods for identifying molecules acting against drug targets in a very short time period, when compared to traditional drug identification strategies. Remdesivir was detected as COVID-19 inhibitory drug via virtual screening method 6. Therefore, keeping the present scenario in our mind, we undertook this study to provide individuals with COVID-19 with drugs already available. Surprisingly, we have found good hits from the databases with medicinal properties.
Artefenomel is known to treat malaria and other parasitic diseases. Betulinic acid is under trial for the treatment of dysplastic nevus syndrome. Atovaquone is an approved drug for the treatment of Pneumocystis carinii pneumonia and malaria. Tetrandrine is in the experimental stage for anticancer, antimalarial, antiparasitic category. Eprinomectin and doramectin are veterinary antiparasitic drugs.
Many of the natural compounds identified have medicinal properties. Taraxerone has allelopathic and antifungal effect 20, Morusin has anti-oxidant and anticancer properties 21, RA VII compound is an antitumor agent 22, and neoruscogenin is used against chronic venous disorders 23. Justicidin D exhibits anti-inflammatory properties 24, Licoricidin is an antimetastatic molecule 25 whereas euphol is used against asthma and cancer along with syphilis, and rheumatism 26. Schisandrene has anti-oxidant activity 27, curine is reported as a vasodilator 27, angoluvarin has antimicrobial activity 28, baicalin is used to treat cardiovascular diseases, inflammation and hypertension 29. Glycyrrhetic acid shows anti-inflammatory, anti-ulcer, hepatoprotective, anti-allergic, anti-tumor, antioxidant and anti-diabetic activity 30. Isomitraphylline has an antioxidant properties 31, bikaverin and rutarensin has anti-tumour activities 32, 33. Jolkinol B has anticancer properties 34 and Ethamidindole exhibits antihistamine properties 35. Fexofenadine acetate, commonly known as Allegra, is an antihistamine pharmaceutical drug presently used in the treatment of allergy symptoms such as urticaria and hay fever 36.
When we compared our two datasets, we found that majority of the molecules showed lesser free binding energy as compared to the reference molecules as in Table 1, Table 2, and Table 3. Surprisingly, we obtained good hits from our natural database which is good news since after observing their interaction and biotherapeutic functions, we might have achieved our COVID-19 inhibitory drugs. One such drug from natural database is fexofenadine acetate (Allegra) which is presently in use as anti-allergic medicine. We also have hits from 129 drugs but there is one, atovaquone, which is presently used against pneumonia and malaria and also a very good candidate for COVID-19 treatment.
Conclusions
The best therapeutic drugs inferred from our studies are atovaquone, fexofenadine acetate (Allegra), justicidin D, baicalin, glycyrrhetic acid and ethamidindole based on their docking score, interaction studies and their present applications for probable COVID-19 treatment. The rest of the molecules could also be used as COVID-19 inhibitory drugs after further evaluation. When we compared our data with reference molecules score of currently in use drug against COVID-19, we found that atovaquone showed better binding energy than hydroxychloroquine and remdesivir. It is one of the best drug candidate for COVID-19 treatment since it is already in use for treating Pneumocystis carinii pneumonia and malaria. Fexofenadine acetate is another good target drug for COVID-19 treatment since it is naturally derived and presently used for its anti-histamine properties. Ethamidindole could possibly act as COVID-19 inhibitor since it is reported as anti-histamine and this novel virus activates cytokine secretion in human body. Apart from these, anti-inflammatory natural molecules such as justicidin D, baicalin, and glycyrrhetic acid could work against COVID-19 since SARS-CoV-2 virus induces inflammation. The rest of the top 20 molecules could also be considered since they all have some medicinal properties as explained above.
Data availability
Source data
The COVID-19 main protease structure was downloaded from the Protein Data Bank, ID 6M03: https://www.rcsb.org/structure/6M03.
Ligands were obtained from PubChem ( https://pubchem.ncbi.nlm.nih.gov/) and the Zinc Natural Products database ( http://zinc.docking.org/).
Extended data
Zenodo: Molecular docking COVID-19. https://doi.org/10.5281/zenodo.3840625 12.
This project contains the following extended data:
Drugs repurposing list (PDF). (PubChem CID of each ligand along with the minimized energy of each molecule and binding affinity results)
Drugs (subfolder). (Interaction images of the reference molecules as well as the best performing target molecules from the 129 docked drugs.)
Natural compounds (subfolder). (Interaction images of the best performing target molecules from the Zinc Natural Products database.)
Results (PDF). (Complete docking results from the Zinc Natural Products database and the list of 129 drugs.)
Extended data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).
Acknowledgements
The authors would like to thank members of the research group ITI for their valuable feedback.
Funding Statement
This work was supported by the research group Infor-mation Technologies Innovation (ITI) (https://www.itiud.org/), which belongs to the Universidad Distrital Francisco Jose de Caldas located in Bogotá Colombia.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
[version 1; peer review: 1 approved
References
- 1. Xu X, Chen P, Wang J, et al. : Evolution of the novel coronavirus from the ongoing Wuhan outbreak and modeling of its spike protein for risk of human transmission. Science China Life Sciences. 2020;63(3):457–460. 10.1007/s11427-020-1637-5 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Zhu N, Zhang D, Wang W, et al. : A novel coronavirus from patients with pneumonia in China, 2019. N Engl J Med. 2020;382(8):727–733. 10.1056/NEJMoa2001017 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3. World Health Organization: Coronavirus disease 2019 (COVID-19) Situation Report - 101. 2020. Reference Source [Google Scholar]
- 4. Jiang F, Deng L, Zhang L, et al. : Review of the clinical characteristics of coronavirus disease 2019 (COVID- 19). J Gen Intern Med. 2020;35(5):1545–1549. 10.1007/s11606-020-05762-w [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5. Chang YC, Tung YA, Lee KH, et al. : Potential therapeutic agents for COVID-19 based on the analysis of protease and RNA polymerase docking. Preprints. 2020; 2020020242. 10.20944/preprints202002.0242.v1 [DOI] [Google Scholar]
- 6. Hall DC, Jr, Ji HF: A search for medications to treat covid-19 via in silico molecular docking models of the sars-cov-2 spike glycoprotein and 3cl protease. Travel Med Infect Dis. 2020;101646. 10.1016/j.tmaid.2020.101646 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7. Jacob RB, Andersen T, McDougal OM: Accessible high-throughput virtual screening molecular docking software for students and educators. PLoS Comput Biol. 2012;8(5): e1002499. 10.1371/journal.pcbi.1002499 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8. Lengauer T, Rarey M: Computational methods for biomolecular docking. Curr Opin Struct Biol. 1996;6(3):402–406. 10.1016/s0959-440x(96)80061-3 [DOI] [PubMed] [Google Scholar]
- 9. Salvatierra K, Florez H: Bioinformatics approach to analyze influenza viruses.In Workshop on Engineering Applications. Springer,2018;442–452. Reference Source [Google Scholar]
- 10. Goldman BB, Wipke WT: Qsd quadratic shape descriptors. 2. molecular docking using quadratic shape descriptors (qsdock). Proteins. 2000;38(1):79–94. [PubMed] [Google Scholar]
- 11. Feig M, Onufriev A, Lee MS, et al. : Performance comparison of generalized born and poisson methods in the calculation of electrostatic solvation energies for protein structures. J Comput Chem. 2004;25(2):265–284. 10.1002/jcc.10378 [DOI] [PubMed] [Google Scholar]
- 12. Singh S, Florez H: Molecular docking covid-19. 2020. 10.5281/zenodo.3840625 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13. Salvatierra K, Vera M, Florez H: Bioinformatics methods to discover antivirals against zika virus. In International Conference on Applied Informatics.Springer,2019;3–14. 10.1007/978-3-030-32475-9_1 [DOI] [Google Scholar]
- 14. Hector F, Karina S: Bioinformatics study of mutations of resistance to antivirals in the ns5a gen of hcv. International Information Institute (Tokyo). Information. 2017;20(9A):6665–6672. Reference Source [Google Scholar]
- 15. Farhadi T, Fakharian A, Ovchinnikov RS: Virtual screening for potential inhibitors of ctx-m-15 protein of klebsiella pneumoniae. Interdiscip Sci. 2018;10(4):694–703. 10.1007/s12539-017-0222-y [DOI] [PubMed] [Google Scholar]
- 16. Rathi S, Ish P, Kalantri A, et al. : Hydroxychloroquine prophylaxis for covid-19 contacts in india. Lancet Infect Dis. 2020; S1473-3099(20)30313-3. 10.1016/S1473-3099(20)30313-3 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17. Meo SA, Klonoff DC, Akram J: Efficacy of chloroquine and hydroxychloroquine in the treatment of covid-19. Eur Rev Med Pharmacol Sci. 2020;24(8):4539–4547. 10.26355/eurrev_202004_21038 [DOI] [PubMed] [Google Scholar]
- 18. Wang Y, Zhang D, Du G, et al. : Remdesivir in adults with severe covid-19: a randomised, double-blind, placebo-controlled, multicentre trial. Lancet. 2020;395(10236):1569–1578. 10.1016/S0140-6736(20)31022-9 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19. Caly L, Druce JD, Catton MG, et al. : The fda-approved drug ivermectin inhibits the replication of sars-cov-2 in vitro. Antiviral res. 2020;178:104787. 10.1016/j.antiviral.2020.104787 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20. Saha D, Dasgupta S, Saha A: Antifungal activity of some plant extracts against fungal pathogens of tea ( camellia sinensis.). Pharma Biol. 2005;43(1):87–91. 10.1080/13880200590903426 [DOI] [Google Scholar]
- 21. Ding B, Lv Y, Zhang YQ: Anti-tumor effect of morusin from the branch bark of cultivated mulberry in bel-7402 cells via the mapk pathway. RSC Adv. 2016;6(21):17396–17404. 10.1039/C5RA21321E [DOI] [Google Scholar]
- 22. Bigot A, Dau MET, Zhu J: Total synthesis of an antitumor agent ra-vii via an efficient preparation of cycloisodityrosine. J Org Chem. 1999;64(17):6283–6296. 10.1021/jo990432w [DOI] [Google Scholar]
- 23. Helleboid S, Haug C, Lamottke K, et al. : The identification of naturally occurring neoruscogenin as a bioavailable, potent, and high-affinity agonist of the nuclear receptor ror α. (nr1f1). J Biomol Screen. 2014;19(3):399–406. 10.1177/1087057113497095 [DOI] [PubMed] [Google Scholar]
- 24. Fukamiya N, Lee KH: Antitumor agents, 81. justicidin-a and diphyllin, two cytotoxic principles from justicia procumbens. J Nat Prod. 1986;49(2):348–350. 10.1021/np50044a030 [DOI] [PubMed] [Google Scholar]
- 25. Park SY, Lim SS, Kim JK, et al. : Hexane-ethanol extract of glycyrrhiza uralensis containing licoricidin inhibits the metastatic capacity of du145 human prostate cancer cells. Br J Nutr. 2010;104(9):1272–1282. 10.1017/S0007114510002114 [DOI] [PubMed] [Google Scholar]
- 26. Mali PY, Shital S: Euphorbia tirucalli l.: Review on morphology, medicinal uses, phytochemistry and pharmacological activities. Asian Pac J Trop Biomed. 2017;7(7):603–613. 10.1016/j.apjtb.2017.06.002 [DOI] [Google Scholar]
- 27. Choi YW, Takamatsu S, Khan SI, et al. : Schisandrene, a dibenzocyclooctadiene lignan from schisandra chinensis: structure-antioxidant activity relationships of dibenzocyclooctadiene lignans. J Nat Prod. 2006;69(3):356–359. 10.1021/np0503707 [DOI] [PubMed] [Google Scholar]
- 28. Hufford CD, Oguntimein BO, Shoolery JN: Angoluvarin, an antimicrobial dihydrochalcone from uvaria angolensis. J Org Chem. 1987;52(23):5286–5288. 10.1021/jo00232a045 [DOI] [Google Scholar]
- 29. Ding L, Jia C, Zhang Y, et al. : Baicalin relaxes vascular smooth muscle and lowers blood pressure in spontaneously hypertensive rats. Biomed Pharmacother. 2019;111:325–330. 10.1016/j.biopha.2018.12.086 [DOI] [PubMed] [Google Scholar]
- 30. Kao TC, Shyu MH, Yen GC: Glycyrrhizic acid and 18 β-glycyrrhetinic acid inhibit inflammation via pi3k/akt/gsk3 β signaling and glucocorticoid receptor activation. J Agric Food Chem. 2010;58(15):8623–8629. 10.1021/jf101841r [DOI] [PubMed] [Google Scholar]
- 31. Azevedo B, Roxo M, Borges M, et al. : Antioxidant activity of an aqueous leaf extract from uncaria tomentosa and its major alkaloids mitraphylline and isomitraphylline in caenorhabditis elegans. Molecules. 2019;24(18):3299. 10.3390/molecules24183299 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32. Limón MC, Rodríguez-Ortiz R, Avalos J: Bikaverin production and applications. Appl Microbiol Biotechnol. 2010;87(1):21–29. 10.1007/s00253-010-2551-1 [DOI] [PubMed] [Google Scholar]
- 33. Yang QY, Tian XY, Fang WS: Bioactive coumarins from boenninghausenia sessilicarpa. J Asian Nat Prod Res. 2007;9(1):59–65. 10.1080/10286020500382397 [DOI] [PubMed] [Google Scholar]
- 34. Lage H, Duarte N, Coburger C: Antitumor activity of terpenoids against classical and atypical multidrug resistant cancer cells. Phytomedicine. 2009;17(6):441–8. 10.1016/j.phymed.2009.07.009 [DOI] [PubMed] [Google Scholar]
- 35. Patnaik GK, Das PK, Dhawan BN, et al. : Pharmacology of ethamidindole, a new antihistaminic agent. Indian J Pharmacol. 1979;11(3):181–187. Reference Source [Google Scholar]
- 36. Kumar L, Shahnwaj Alam Md, Lal Meena C, et al. : Fexofenadine hydrochloride. Profiles of drug substances, excipients and related methodology. 2009;34:153–192. Elsevier. Reference Source [DOI] [PubMed] [Google Scholar]