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Chemistry Central Journal logoLink to Chemistry Central Journal
. 2017 Jan 30;11:11. doi: 10.1186/s13065-017-0240-1

Cheminformatics studies to analyze the therapeutic potential of phytochemicals from Rhazya stricta

Abdullah Y Obaid 1, Sreedhara Voleti 2, Roop Singh Bora 3,4, Nahid H Hajrah 3, Abdulkader M Shaikh Omer 5, Jamal S M Sabir 3, Kulvinder Singh Saini 3,4,
PMCID: PMC5280814  PMID: 28194226

Abstract

Rhazya stricta is a unique medicinal plant source for many indole alkaloids, non-alkaloids, flavonoids, triterpenes and other unknown molecules with tremendous potential for therapeutic applications against many diseases. In the present article, we generated computational data on predictive properties and activity across two key therapeutic areas of cancer and obesity, and corresponding cheminformatics studies were carried out to examine druggable properties of these alkaloids. Computed physiochemical properties of the 78 indole alkaloids from R. stricta plant using industry-standard scientific molecular modeling software and their predictive anti-cancer activities from reliable web-source technologies indicate their plausible therapeutic applications. Their predictive ADME properties are further indicative of their drug-like-ness. We believe that the top-ranked molecules with anti-cancer activity are clearly amenable to chemical modifications for creating potent, safe and efficacious compounds with the feasibility of generating new chemical entities after pre-clinical and clinical studies.

Keywords: Rhazya stricta, Alkaloids, Physiochemical properties, Druggability, Anticancer molecules, Anti-obesity molecules

Background

Rhazya stricta Decsne (Apocynaceae family), a traditional herbal medicinal plant from Western and South Asia, has been shown to have multiple pharmacological effects due to the presence of over 100 alkaloids [13]. The chemical constituents of this plant (R. stricta) may possess biological activities of antifungal, antimicrobial, antioxidant, CNS, hypertension, metabolic, and inflammatory disorders. Rhazimine, an alkaloid isolated from R. stricta leaves, was shown to affect arachidonic acid metabolism in human blood [4]. This alkaloid was shown to be a dual and selective inhibitor of platelet activating factor (PAF)-induced platelet aggregation and arachidonic acid metabolism. Other effects of the lyophilized extract of R. stricta include an antispasmodic effect in rat muscles [5]. In another study, antioxidant effects were observed at higher doses, and it reduced the hepatic and renal concentrations of glutathione (GSH) and increased the ascorbic acid levels, whereas the degree of lipid peroxidation was reduced [6]. A recent study has shown that the basic alkaloid fraction from R. stricta significantly induces one of the chemopreventive enzyme-Nqo 1, through an Nrf 2-dependent mechanism, thereby establishing its role as an anti-tumor agent [7]. In another pharmacological study, the biochemical parameters including blood lipid profile concentrations, liver enzyme activities and kidney functions were analyzed in rats [8]. It was also found that aqueous extract of R. stricta and indole alkaloids caused a significant increase in serum adiponectin levels and resulted in significant improvements in insulin resistance [9]. In another follow up study, we observed indole-alkaloids of R. stricta improved not only the lipid profile and liver function but also led to improvements in the insulin levels in rats, most likely via modulating insulin resistance [10]. Indole-alkaloids of R. stricta had been reported to have anticancer properties [11]. Other studies by our departmental colleagues showed that alkaloid extract of R. stricta leaves inhibited proliferation, colony formation and anchorage-independent growth in various cancer cell lines such as colon cancer, breast cancer and lung cancer [1214].

Understanding the chemical structure, physiochemical, and chemical-informatic properties of these natural product compounds will give clues for further modifications required in their structures responsible for their biological activities. Even though, there have been about 100 chemical entities of indole-based alkaloid constituents of R. stricta which have been reported but their chemical structures are yet to be clustered and identified, and moreover the pharmacological application of any one of these constituents towards human health is yet to be identified. Understanding qualitative correlation of structures to their chemical druggability, IP potential, and their applicability towards a therapeutic area would be worth exploring prior to pre-clinical studies. Availability of this plant (R. stricta), thus its phytochemical constituents largely in Arabian and South Asian region makes it worth studying through computational, synthetic, and biological view point. Indole based alkaloids such as vinblastine and vincristine are well known for their anti-cancer properties. From systematically generated informatics data analysis, one would be able to evaluate the physiochemical properties of the potential therapeutic compounds. These promising molecules which have “desirable pharmacophores” may provide obvious extension to a better targeted therapeutic benefit. Conventional drugs obey set of rules such as Lipinski’s Rule-of-Five (RO5) [15], wherein all orally administered molecules need to have certain physiochemical properties. Calculation of these cheminformatic properties has thus become essential for all projects of new drug discovery which go through oral route of administration. Along with RO5, the new molecules also have to adhere to certain parameters which yield favorable ADMET outcome of an oral drug. We further evaluated these molecules for therapeutic activity, including anticancer, anti-obesity, anti-inflammatory, and anti-bacterial properties. Although these predictions are indicative only, the value of predictions in various target classes and therapeutic areas would be very useful for future experimental studies. Moreover, their metabolic fate with key enzymes such as P450’s is also predicted for probable drug–drug and drug-target (P450) interactions (reviewed in [16, 17]).

Methods

For prediction of various therapeutic potential of these molecules, commercially and publicly available technologies as below were utilized.

  1. PharmaExpert (http://www.pharmaexpert.ru)—PASS [18]

  2. Superpred (http://prediction.charite.de)—Predictive Targets [19]

  3. SwissTargetPrediction (http://www.swisstargetprediction.ch)—Predictive Target [20]

  4. CDRUG (http://bsb.kiz.ac.cn/CDRUG)—Anti-cancer activity [21]

Schrodinger [22], a scientific software that predicts drug-like properties and liabilities (viz. HERG and CNS), and ACD/Labs [23] for physiochemical and cheminformatics studies were utilized. Details of the molecules, names, structures were obtained from the literature, commercial sources, and knowledge-based web sources. Tables 1 and 2 gives the details of these molecules together with their 2D SMILES notation, respectively.

Table 1.

Chemical structures and names of Rhazya stricta compounds

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Table 2.

SMILES codes for Rhazya stricta compounds

MOL ID Name SMILES code
M1 Akummidine COC(=O)C1(CO)C2CC3=C([NH]C4=C3C=CC=C4)C5CC1\C(CN25)=C/C
M2 Antirhine OCC(C=C)C1CCN2CCC3=C([NH]C4=C3C=CC=C4)C2C1
M3 3-Epi-antirhine OCC(C=C)C1CCN2CCC3=C([NH]C4=C3C=CC=C4)C2C1
M4 Aspidosespermidine CCC12CCCN3CCC4(C(CC1)NC5=C4C=CC=C5)C23
M5 Condylocarpine COC(=O)C1=C2NC3=CC=CC=C3C24CCN5CCC1\C(=C\C)C45
M6 Dihydrocorynantheol CCC1CN2CCC3=C([NH]C4=CC=CC=C34)C2CC1CCO
M7 Eburnamenine CCC12CCCN3CCC4=C(C13)[N](C=C2)C5=CC=CC=C45
M8 Eburnamine CCC12CCCN3CCC4C(C13)[N](C(O)C2)C5=CC=CC=C45
M9 Eburnamonine CCC12CCCN3CCC4=C(C13)[N](C(=O)C2)C5=CC=CC=C45
M10 Geissoschizine COC(=O)\C(=C/O)C\1CC2N(CCC3=C2[NH]C4=CC=CC=C34)CC1=C\C
M11 Isositsirikine COC(=O)C(CO)C\1CC2N(CCC3=C2[NH]C4=CC=CC=C34)CC1=C/C
M12 16-Epi-Z-isositsirikine COC(=O)C(CO)C\1CC2N(CCC3=C2[NH]C4=CC=CC=C34)CC1=C\C
M13 Leuconalm CCC12CCCN3C(=O)C=C(C4=CC=CC=C4NC(=O)CC1)C23O
M14 Rhazinliam CCC12CCC[N]3C=CC(=C13)C4=CC=CC=C4NC(=O)CC2
M15 Tetrahydrosecamine CCC1CCCN(CCC2=C([NH]C3=CC=CC=C23)C4(CCC(C(=O)OC)C5=C(CCN6CCCC(CC)C6)C7=C
C=CC=C7[N]45)C(=O)OC)C1
M16 Presecamine CCC1=CCCN(CCC2=C([NH]C3=CC=CC=C23)OC(=O)C4CCC(=C5N(C)C6=C C=CC=C6C45C
CN7CCC=C(CC)C7)C(=O)OC)C1
M17 Sewarine COC(=O)C1=C2NC3=C(C=C(O)C=C3)C24CCN5C\C(=C\C)C1CC45
M18 Stemmadenine C\C=C1/CN2CCC1C(C(=O)OCO)C3=C(CC2)C4=CC=CC=C4[N]3C
M19 Strictamine COC(=O)C1C\2CC3N(CCC14C3=NC5=CC=CC=C45)CC2=C\C
M20 Strictosamide OCC1OC(OC2OC=C3C(CC4N(CCC5=C4[NH]C6=CC=CC=C56)C3=O)C2C=C)C(O)C(O)C1O
M21 Strictosidine COC(=O)C1=COC(OC2OC(CO)C(O)C(O)C2O)C(C=C)C1CC3NCCC4=C3[NH]C5=CC=CC=C45
M22 Taberonine CCC12CC(=C3NC4=CC=CC=C4C35CCN(CC=C1)C25)C(=O)OC
M23 Tetrahydrlstonine COC(=O)C1=COC(C)C2CN3CCC4=C([NH]C5=CC=CC=C45)C3CC12
M24 Vallesiachotamine COC(=O)C1=CN2CCC3=C([NH]C4=CC=CC=C34)C2CC1\C(=C/C)C=O
M25 Aspidospermoise CCC12CCCN3CCC4(C(CC1)N(C5OC(O)C(=O)C(O)C5O)C6=CC=CC=C46)C23
M26 Bhimbrine COC(=O)C(CO)C\1CC2N(CCC3=C2[NH]C4=C3C=CC=C4)CC1=C/C
M27 Bhimbrine N-oxide COC(=O)C(CO)C\1CC2C3=C(CC[N+]2([O-])CC1=C/C)C4=C([NH]3)C=CC=C4
M28 Rhazimine COC(=O)C12C(CC3(C=NC4=CC=CC=C34)C1=O)N5CCC2\C(C5)=C/C
M29 Rhazimanine COC(=O)C(CO)C\1CC2N(CCC3=C2[NH]C4=CC=CC=C34)CC1=C\C
M30 Rhazicine COC(=O)C12C(CC3(C(O)NC4=CC=CC=C34)C1=O)N5CCC2\C(C5)=C\C
M31 Leepacine COC(=O)C12C3CC4(C(NC5=CC=CC=C45)C6CC1\C(CN36)=C/C)C2=O
M32 2-Methoxy 1-2,dihydrorhazamine COC1NC2=CC=CC=C2C13CC4N5CCC(\C(C5)=C/C)C4(C(=O)OC)C3=O
M33 HR-1 C\C=C1\C[N+]2([O-])CCC3=C(C2CC1(O)COC(C)=O)[N](C)C4=CC=CC=C34
M34 Vincanicine COC1=CC=C2C(=C1)NC3=C(C=O)C\4CC5N(CCC235)CC4=C\C
M35 Rhazinaline COC(=O)C1(C=O)C\2CC3N(CCC14C3=NC5=CC=CC=C45)CC2=C/C
M36 Beta-sitosterol CCC(CCC(C)C1CCC2C3CC=C4CC(O)CCC4(C)C3CCC12C)C(C)C
M37 Ursolic acid CC1CCC2(CCC3(C)C(=CCC4C5(C)CCC(O)C(C)(C)C5CCC34C)C2C1C)C(O)=O
M38 Stigmasterol CCC(\C=C\C(C)C1CCC2C3CC=C4CC(O)CCC4(C)C3CCC12C)C(C)C
M39 Olenaolic acid CC1(C)CCC2(CCC3(C)C(=CCC4C5(C)CCC(O)C(C)(C)C5CCC34C)C2C1)C(O)=O
M40 Rhazidigenine (rhazidine) CCC12CCCN(CCC3(O)C(=NC4=CC=CC=C34)CC1)C2
M41 N-methylleuconolam CCC12CCCN3C(=O)C=C(C4=CC=CC=C4N(C)C(=O)CC1)C23O
M42 (+)-Quebranchamine CCC12CCCN(CCC3=C(CC1)[NH]C4=CC=CC=C34)C2
M43 Polyneuridine COC(=O)C1(C=O)C2CC3=C([NH]C4=CC=CC=C34)C5CC1\C(CN25)=C\C
M44 (+)-Vincadiformine CCC12CCCN3CCC4(C13)C(=C(C2)C(=O)OC)NC5=CC=CC=C45
M45 (−)-Vincadiformine CCC12CCCN3CCC4(C13)C(=C(C2)C(=O)OC)NC5=CC=CC=C45
M46 Secamine CCC1=CCCN(CCC2=C([NH]C3=C2C=CC=C3)C4(CCC(C(=O)OC)C5=C (CCN6CCC=C(CC)
C6)C7=CC=CC=C7[N]45)C(=O)OC)C1
M47 Vincadine CCC12CCCN(CCC3=C([NH]C4=CC=CC=C34)C(C1)C(=O)OC)C2
M48 Bis-strictidine CCC1=C2C3CC4(CCN2CCC1)C5C=CC=CC5 N=C4C6CC7(CCN8CCCC(=C68)
CC)C3=NC9=C7C=CC=C9
M49 3,14-Dehydrorhazigine CCC1=CN(CCC1)CCC2C(=NC3=C2C=CC=C3)C4CCC(=C5NC6=C(C=CC=C6) C45C
CN7CC(=CC=C7)CC)C(=O)OC
M50 16-Hydrorhazisidine CCC1=CCCN(CCC2=C3C(CC(C(O)[N]3C4=C2C=CC=C4)C5=C(CCN6CCCC(=C6)CC)
C7=C([NH]5)C=CC=C7)C(=O)OC)C1
M51 Rhazisidine CCC1=CCCN(CCC2=C3C(CC4C([N]3C5=C2C=CC=C5)C6=C(CC)C=C CN6C
CC7=C4[NH]C8=C7C=CC=C8)C(=O)OC)C1
M52 Isorhazicine COC(=O)C12C(CC3(C(O)NC4=C3C=CC=C4)C1=O)N5CCC2\C(C5)=C\C
M53 Rhazigine CCC1=CCCN(CCC2=C([NH]C3=C2C=CC=C3)C4CCC(=C5NC6=C(C=CC=C6) C45C
CN7CCC=C(CC)C7)C(=O)OC)C1
M54 Strictisidine COC(=O)C12C3CC4(C1=O)C(=NC5=C4C=CC=C5)C6CC2\C(CN36)=C\C
M55 Strictamine-N-oxide COC(=O)C1C\2CC3C4=NC5=CC=CC=C5C14CC[N +]3([O-])CC2=C/C
M56 Strictigine CCC1=C2CCN(CCC23C(=NC4=CC=CC=C34)C=C)C1
M57 Strictine COC(=O)C1C2CC3 N(CCC4=C3[N]1C5=CC=CC=C45)C=C2C(C)=O
M58 Stricticine COC(=O)C1=C2NC3=CC=CC=C3C24CCN5CC6(OC6C)C1CC45
M59 Strictalamine C\C=C1/CN2CCC34C(C=O)C1CC2C3=NC5=CC=CC=C45
M60 1,2-Dehydroaspidospermine CCC12CCCN3CCC4(C13)C(=NC5=CC=CC=C45)CC2
M61 Tetrahydrosecodine CCC1CCCN(CCC2=C([NH]C3=CC=CC=C23)C(C)C(=O)OC)C1
M62 Dihydrosecodine CCC1=CCCN(CCC2=C([NH]C3=CC=CC=C23)C(C)C(=O)OC)C1
M63 Dihydrosecamine CCC1CCCN(CCC2=C([NH]C3=C2C=CC=C3)C4(CCC(C(=O)OC)C5=C (CCN6CC
C=C(CC)C6)C7=CC=CC=C7[N]45)C(=O)OC)C1
M64 Dihydropresecamine CCC1CCCN(CCC2=C([NH]C3=CC=CC=C23)OC(=O)C4CCC(=C5 N© C6=CC=C
C=C6C45CCN7CCC=C(CC)C7)C(=O)OC)C1
M65 Tetrahydropresecamine CCC1CCCN(CCC2=C([NH]C3=CC=CC=C23)OC(=O)C4CCC(=C5 N© C6=CC=C
C=C6C45CCN7CCCC(CC)C7)C(=O)OC)C1
M66 Rhazinol C\C=C1\CN2CCC34C(CO)C1CC2C3=NC5=CC=CC=C45
M67 Rhazimol COC(=O)C1(CO)C\2CC3N(CCC14C3=NC5=CC=CC=C45)CC2=C/C
M68 Rhazidigenine-N-oxide CCC12CCC[N+]([O-])(CCC3(O)C(=NC4=CC=CC=C34)CC1)C2
M69 (−)-16R,21R-Omethyleburmanine CCC12CCCN3CCC4=C(C13)[N](C(C2)OC)C5=CC=CC=C45
M70 Decarbomethoxy-15,20,16,17-tetrahydrosecodine CCC1CCCN(CCC2=C(CC)[NH]C3=CC=CC=C23)C1
M71 1,2-Dehydroaspidospermidine-N-oxide CCC12CCC[N+]3([O–])CCC4(C13)C(=NC5=CC=CC=C45)CC2
M72 Rhazizine COC(=O)C12OCN3C(O1)C4(CCN5C\C(=C\C)C2CC45)C6=CC=CC=C36
M73 15-Hydroxyvincadifformine CCC12CC(=C3NC4=CC=CC=C4C35CCN(CCC1O)C25)C(=O)OC
M74 Dihydroburnamenine CCC12CCCN3CCC4=C(C13)[N](CC2)C5=CC=CC=C45
M75 16s,16′-Decarboxytetrahydrosecamine CCC1CCCN(CCC2=C([NH]C3=C2C=CC=C3)C4CCC(C(=O)OC)C5=C
(CCN6CCCC(CC)C6)C7=C(C=CC=C7)[N]45)C1
M76 Nor-C-fluorocuraine C\C=C1\CN2CCC34C2CC1C(=C3NC5=CC=CC=C45)C=O
M77 Strictibine COC(=O)C1=CC=C2NC3=CC=CC=C3C12

Results and discussion

Physiochemical and cheminformatic studies

ACD/Laboratories informatics modules generated physiochemical and cheminformatics data of R. stricta indole and non-indole alkaloids. For all the selected 78 molecules in this study, it was observed that less than 20% of the molecules are having molecular weights >450, while most molecules range around 300–350, indicating their viability for additional medicinal chemistry amenable nature. Most of these molecules are also moderately to highly soluble—mainly due to the high value of pKa (leading to solubility at neutral pH). Additionally, many of these indole/non-indole molecules are also less lipophilic (~75% of them have logP ~3 to 4). Alkaloids that violate Lipinski’s Rule-of-5 are either due to molecular weight or logP, are tetrahydrosecamine; presecamine; beta-sitosterol; ursolic acid; stigmasterol; oleanolic acid; secamine; bis-strictidine; 3,14-dehydrorhazigine; 16-hydroxyrhazisidine; rhazisidine; rhazigine; dihydrosecamine; dihydropresecamine; tetrahydropresecamine; decarbomethoxy-15,17-tetrahydrosecodine;16s,16′-decarboxytetrahydro-secamine. Figures 1 and 2 give the plots of molecular weight and LogP (lipophilicity) of individual compounds, accordingly. Since most of the molecules have a basic nitrogen and sometimes, may be more than one, leading to a larger pKa at physiological pH—thus leading most molecules are highly to moderately soluble at physiological pH. Very few compounds and non-indole alkaloids have no basic nitrogen leading to highly insoluble compounds in water at physiological pH. As the acidity goes up (leading towards pH 1), most compounds become largely soluble. A qualitative and quantitative (computational) estimate of solubility of these compounds are given in Tables 3 and 4, respectively.

Fig. 1.

Fig. 1

Variation of Molecular weight of compounds of Rhazya stricta

Fig. 2.

Fig. 2

Variation of LogP of compounds of Rhazya stricta

Table 3.

Qualitative assessment of Rhazya stricta compounds with respect to Lipinski’s Rule-of-5 and solubility

ID Name LogP MW HBD HBA #RotB Rings Rule-of-5 Leadlike Solubility
1 Akummidine Optimal Good Good Good Good Bad Good Good Soluble
2 Antirhine Optimal Good Good Good Good Good Good Good Soluble
3 3-epi-Antirhine Optimal Good Good Good Good Good Good Good Soluble
4 Aspidosespermidine Optimal Good Good Good Good Bad Good Good Soluble
5 Condylocarpine Optimal Good Good Good Good Bad Good Good Soluble
6 Dihydrocorynantheol Optimal Good Good Good Good Good Good Good Soluble
7 Eburnamenine Lipophilic Good Good Good Good Bad Good Moderate Soluble
8 Eburnamine Optimal Good Good Good Good Bad Good Good Soluble
9 Eburnamonine Optimal Good Good Good Good Bad Good Good Soluble
10 Geissoschizine Optimal Good Good Good Good Good Good Good Insoluble
11 Isositsirikine Optimal Good Good Good Good Good Good Good Soluble
12 16-Epi-Z-isositsirikine Optimal Good Good Good Good Good Good Good Soluble
13 Leuconalm Optimal Good Good Good Good Good Good Good Soluble
14 Rhazinliam Lipophilic Good Good Good Good Good Good Moderate Highly insoluble
15 Tetrahydrosecamine Very lipophilic Bad Good Good Bad Bad Bad Bad Soluble
16 Presecamine Very lipophilic Bad Good Good Bad Bad Bad Bad Soluble
17 Sewarine Optimal Good Good Good Good Bad Good Good Soluble
18 Stemmadenine Optimal Good Good Good Good Bad Good Good Soluble
19 Strictamine Optimal Good Good Good Good Bad Good Good Insoluble
20 Strictosamide Optimal Moderate Good Good Good Bad Good Bad Soluble
21 Strictosidine Optimal Bad Bad Bad Good Bad Bad Bad Soluble
22 Taberonine Optimal Good Good Good Good Bad Good Good Soluble
23 Tetrahydrlstonine Optimal Good Good Good Good Bad Good Good Soluble
24 Vallesiachotamine Optimal Good Good Good Good Good Good Good Highly insoluble
25 Aspidospermoise Optimal Good Good Good Good Bad Good Good Soluble
26 Bhimbrine Optimal Good Good Good Good Good Good Good Soluble
27 Bhimbrine N-oxide Optimal Good Good Good Good Good Good Good Soluble
28 Rhazimine Optimal Good Good Good Good Bad Good Good Soluble
29 Rhazimanine Optimal Good Good Good Good Good Good Good Soluble
30 Rhazicine Optimal Good Good Good Good Bad Good Good Soluble
31 Leepacine Optimal Good Good Good Good Bad Good Good Soluble
32 2-Methoxy,1-2,dihydro rhazamine Optimal Good Good Good Good Bad Good Good Soluble
33 HR-1 Optimal Good Good Good Good Good Good Good Soluble
34 Vincanicine Optimal Good Good Good Good Bad Good Good Soluble
35 Rhazinaline Optimal Good Good Good Good Bad Good Good Insoluble
36 Beta-sitosterol Very lipophilic Lipophilic Good Good Good Good Good Moderate Moderate
37 Ursolic acid Very lipophilic Lipophilic Good Good Good Good Bad Moderate Highly insoluble
38 Stigmasterol Lipophilic Good Good Good Good Good Moderate Moderate Insoluble
39 Olenaolic acid Very lipop Lipophilic Good Good Good Good Bad Moderate Highly insoluble
40 Rhazidigenine (rhazidine) Optimal Optimal Good Good Good Good Good Good Good
41 N-methylleuconolam Optimal Good Good Good Good Good Good Good Soluble
42 (+)-Quebranchamine Lipophilic Good Good Good Good Good Good Moderate Soluble
43 Polyneuridine Optimal Good Good Good Good Bad Good Good Soluble
44 (+)-Vincadiformine Optimal Good Good Good Good Bad Good Good Soluble
45 (−)-Vincadiformine Optimal Good Good Good Good Bad Good Good Soluble
46 Secamine Very Lipop Bad Good Good Bad Bad Bad Bad
47 Vincadine Optimal Good Good Good Good Good Good Good Soluble
48 Bis-strictidine Very lipop Bad Good Good Good Bad Bad Bad Insoluble
49 3,14-Dehydrorhazigine Very lipop Bad Good Good Bad Bad Bad Bad Highly insoluble
50 16-Hydrorhazisidine Very lipop Bad Good Good Bad Bad Bad Bad Soluble
51 Rhazisidine Very lipop Bad Good Good Good Bad Bad Bad Insoluble
52 Isorhazicine Optimal Good Good Good Good Bad Good Good Soluble
53 Rhazigine Very lipop Bad Good Good Bad Bad Bad Bad Soluble
54 Strictisidine Optimal Good Good Good Good Bad Good Good Soluble
55 Strictamine-N-oxide Optimal Good Good Good Good Bad Good Good Soluble
56 Strictigine Optimal Good Good Good Good Bad Good Good Soluble
57 Strictine Optimal Good Good Good Good Bad Good Good Highly insoluble
58 Stricticine Optimal Good Good Good Good Bad Good Good Soluble
59 Strictalamine Optimal Good Good Good Good Bad Good Good Insoluble
60 1,2-Dehydro-aspidospermine Optimal Good Good Good Good Bad Good Good Soluble
61 Tetrahydrosecodine Lipophilichilic Good Good Good Good Good Good Moderate Soluble
62 Dihydrosecodine Lipophilichilic Good Good Good Good Good Good Moderate Soluble
63 Dihydrosecamine Very lipophilic Bad Good Good Bad Bad Bad Bad Soluble
64 Dihydropresecamine Very lipophilic Bad Good Good Bad Bad Bad Bad Soluble
65 Tetrahydropresecamine Very lipop Bad Good Good Bad Bad Bad Bad Soluble
66 Rhazinol Optimal Good Good Good Good Bad Good Good Insoluble
67 Rhazimol Optimal Good Good Good Good Bad Good Good Insoluble
68 Rhazidigenine-N-oxide Optimal Good Good Good Good Good Good Good Soluble
69 (−)-16R,21R-Omethyleburmanine Optimal Good Good Good Good Bad Good Good Soluble
70 Decarbomethoxy-15,20,16,17-tetrahydrosecodine Very lipophilic Good Good Good Good Good Moderate Moderate Soluble
71 1,2-Dehydroaspidosper midine-N-oxide Optimal Good Good Good Good Bad Good Good Soluble
72 Rhazizine Optimal Good Good Good Good Bad Good Good Soluble
73 15-Hydroxyvincadiffor mine Optimal Good Good Good Good Bad Good Good Soluble
74 Dihydroburnamenine Lipophilic Good Good Good Good Bad Good Moderate Soluble
75 16s,16′-Decarboxytetra hydrosecamine Very lipop Bad Good Good Bad Bad Bad Bad Soluble
76 Nor-C-fluorocuraine Optimal Good Good Good Good Bad Good Good Soluble
77 Strictibine Optimal Good Good Good Good Good Good Good Insoluble

LogP partition-coefficient, MW molecular weight, HBD hydrogen bond donor, HBA hydrogen bond acceptors, #RotB number of rotatable bonds, Rings # of ideally acceptable rings, Rule-of-5 Lipinski’s rule of five, Leadlike leadlikeness, Solubility solubility classification

Table 4.

Predicted solubility and pKa (acid and base) of various Rhazya stricta compounds

ID Name Solubility LogSW/LogSw LogSw/pH pKa (acid) pKa (base)
1 Akuammidine Soluble −3.32 8.85 14.79 6.88
2 Antirhine Soluble −4.08 9.49 14.72 9.24
3 3-Epi-antirhine Soluble −4.08 9.49 14.72 9.24
4 Aspidosespermidine Soluble −2.34 10.82 9.94
5 Condylocarpine Soluble −3.13 9.36 7.98
6 Dihydrocorynantheol Soluble −4.04 9.57 15.08 9.37
7 Eburnamenine Soluble −4.6 8.92 8.61
8 Eburnamine Soluble −4.39 9.15 14.3
9 Eburnamonine Soluble −4.4 8.82 8.13
10 Geissoschizine Insoluble −3.64 6.59 4.73 8.25
11 Isositsirikine Soluble −4.1 9.16 14.29 8.49
12 16-Epi-Z-isositsirikine Soluble −4.1 9.16 14.29 8.49
13 leuconolam Soluble −1.83 6.71 11.76 0.36
14 Rhazinilam Highly insoluble −4.47 7 1.21
15 Tetrahydrosecamine Soluble −3.67 8.07 17.43 9.4
16 Presecamine Soluble −5.27 8.48 15.79 8.54
17 Sewarine Soluble −2.98 9.17 11.08 1.95
18 Stemmadenine Soluble −3.63 9.21 11.84 8.08
19 Strictamine Insoluble −4.47 7.7 5.74
20 Strictosamide Soluble −3.26 7 12.79 −1.64
21 Strictosidine Soluble −2.73 10.83 12.81 10.62
22 Tabersonine Soluble −2.99 9.25 7.64
23 Tetrahydroalstonine Soluble −4.4 8.89 18.03 8.27
24 Vallesiachotamine Highly insoluble −5.21 7.45 17.46 6.08
25 Aspidospermiose Soluble −0.19 9.81 10.11 9.88
26 Bhimberine Soluble −4.1 9.16 14.29 8.49
27 Bhimbhrine N-oxide Soluble 0.4 9.66 14.2 5.17
28 Rhazimine Soluble −2.89 8.9 6.51
29 Rhazimanine Soluble −4.1 9.16 14.29 8.49
30 Rhazicine Soluble −1.6 8.94 11.3 6.36
31 Leepacine Soluble −1.84 9.43 6.69
32 2-Methoxy-1,2-dihydrorhazimine Soluble −2.18 9.15 6.3
33 HR-1 Soluble 0.43 8.55 12.69 4.6
34 Vincanicine Soluble −2.67 9.67 8.16
35 Rhazinaline Insoluble −4.14 7.47 5.03
36 Beta-sitosterol Highly insoluble −7.6 7 15.03
37 Ursolic acid Highly insoluble −6 6.01 15.18
38 Stigmasterol Highly insoluble −7.52 7 15.03
39 Oleanolic acid Highly insoluble −6.02 6.04 15.18
40 Rhazidigenine Soluble −3.2 9.92 12.43 8.82
41 N-methylleuconolam Soluble −1.52 6.55 11.62 0.09
42 (+)-Quebrachamine Soluble −4.15 9.55 17.84 9.74
43 Polyneuridine Soluble −3.2 8.46 17.19 6.11
44 (+)-Vincadiformine Soluble −3.06 10.04 9.33
45 (−)-Vincadifformine Soluble −3.06 10.04 9.33
46 Secamine Soluble −5.12 8.22 17.34 8.71
47 Vincadine Soluble −4.23 9.28 16.98 9.11
48 Bis-strictidine Insoluble −6.11 7.79 7.57
49 3,14-Dehydrorhazigine Highly insoluble −5.89 8.12 10.62
50 16-Hydrorhazisidine Soluble −5.05 8.28 13.98 10.8
51 Rhazisidine Insoluble −5.56 8.2 17.47 8.76
52 Isorhazicine Soluble −1.6 8.94 11.3 6.36
53 Rhazigine Soluble −4.44 7.7 17.45 8.89
54 Strictisidine Soluble −2.18 8.18 4.27
55 Strictamine-N-oxide Soluble −0.67 8.73 4.17
56 Strictigine Soluble −4.07 8.83 7.71
57 Strictine Highly insoluble −4.79 7.36 5.41
58 Stricticine Soluble −3.68 9.33 8.43
59 Strictalamine Insoluble −3.94 8.04 5.87
60 1,2-Dehydroaspidospermidine(eburenine) Soluble −2.84 10.23 9.38
61 Tetrahydrosecodine Soluble −3.85 9.67 16.75 9.33
62 Dihydrosecodine Soluble −3.84 9.44 16.66 8.73
63 Dihydrosecamine Soluble −4.61 8.3 17.43 9.4
64 Dihydropresecamine Soluble −4.78 8.28 15.88 9.16
65 Tetrahydropresecamine Soluble −3.89 8.23 15.88 9.65
66 Rhazinol Insoluble −4.1 8.25 14.53 6.3
67 Rhazimol Insoluble −4.24 7.67 14.53 5.45
68 Rhazidigenine-N-oxide Soluble 0.5 8.35 11.98 49.2
69 (−)16R,21R-omethyleburnamine Soluble −4.93 8.73 8.66
70 Decarbomethoxy-15,20,16,17-tetrahydros Soluble −3.79 9.81 17.83 9.46
71 1-2-Dehydroasidospermidine-N-oxide Soluble −1.2 8.95 4.82
72 Rhazizine Soluble −2.61 9.2 7.31
73 15-Hydroxyvincadifformine Soluble −2.36 9.88 14.4 8.46
74 Dihydroeburnamenine Soluble −4.72 9.06 9.41
75 16s,16’-Decarboxytetra-hydrosecamine Soluble −3.5 7.88 17.43 9.4
76 Nor-C-fluorocurarine Soluble −2.4 9.8 8.14
77 Strictibine Insoluble −3.7 7 1.06

Solubility solubility classifications, LogSW/LogSw ratio of solubility in water vs. intrinsic solubility, LogSw/pH solubility in water at pH 7.0, pKa (acid) pKa in acidic pH, pKa(base) pKa in basic pH

QUIKPROP calculations

Predicted Quikprop properties for potential cardiac liabilities such as HERG, and CNS liabilities (Blood–Brain-Barrier) and drug-like nature of these molecules indicate that many of these molecules are well within the boundaries of accepted hit-, and lead-like nature. QuikProp calculations were performed using Schrodinger’s Maestro for various alkaloids of R. stricta. These predictions not only give Rule-of-5 data, but also predict the cardiotoxicity predictions (HERG) and CNS penetration potential (logBBB) properties. More importantly, it also gives the prediction regarding cell-permeability (Caco2). All these models are well validated in literature, and most of them perform well within the reproducible results for training datasets. Results indicate that many of the molecules have decent permeation through Caco2 cell lines (>300), while the polar surface area (PSA) is not too high (>120) for oral absorption. For HERG toxicity prediction, below −5 (i.e. −6, −7 etc.) is not considered to be safe. Hence, those molecules whose logHERG values are well below -5 (such as geissoschizine, presecamine, tetrahydrosecamine) may exhibit cardioliability. The human intestinal absorption is also predicted, and it appears for most molecules, these values are larger. Any %HIA prediction >90% is expected to be well absorbed, and their polar surface area (PSA) is also a direct correlation to it. Those molecules whose molecular weights are >500 exhibit rule-of-5 violation and this violation goes beyond 1 to a maximum of 3. Those molecules appear structurally much larger and like dimers. Table 5 gives computed Quikprop computed values of various alkaloids of R. stricta. Table 6 also indicates various other physiochemical parameters including surface tension, parachor etc. of R. stricta indole and non-indole analogs.

Table 5.

Quikprop calculation (for physiochemical properties) of Rhazya stricta compounds

Title Name M.W HBD HBA QP logP QP logS QP logHERG QP Caco2 QP logBB %HOA PSA RO5v
M1 Akummidine 352.432 1 5 3.2 −3.5 −5.1 410.4 0.1 93 63 0
M2 Antirhine 296.411 2 4 3.1 −3.3 −5.6 583.1 0.1 95 40 0
M3 3-Epi-antirhine 296.411 2 4 3.1 −3.3 −5.6 583.1 0.1 95 40 0
M4 Aspidosespermidine 282.428 1 3 2.8 −1.9 −5.2 382.4 1.1 90 18 0
M5 Condylocarpine 322.406 0 3 4 −4.5 −5.5 735.5 0.4 100 48 0
M6 Dihydrocorynantheol 298.427 2 4 3.2 −3.6 −5.7 521.2 0.1 95 40 0
M7 Eburnamenine 278.396 0 2 4.1 −3.7 −5.2 2375.6 0.9 100 7 0
M8 Eburnamine 296.411 1 4 3.2 −3.1 −4.9 1159.1 0.5 100 27 0
M9 Eburnamonine 294.396 0 5 2.4 −2.1 −4.8 1051.6 0.6 95 32 0
M10 Geissoschizine 352.432 1 6 3 −4.4 −6.2 202.7 −0.4 86 79 0
M11 Isositsirikine 354.448 1 5 3.6 −3.9 −5.5 348.3 −0.1 94 68 0
M12 16-Epi-Z-isositsirikine 354.448 1 5 3.7 −4.6 −6.1 305.6 −0.2 93 71 0
M13 Leuconalm 326.394 2 6 2 −3.3 −3.7 600.6 −0.6 88 82 0
M14 Rhazinliam 294.396 1 3 4.1 −4.6 −4.2 3342.3 0.1 100 36 0
M15 Tetrahydrosecamine 680.929 0 7 8.5 −8.1 −8.1 198.9 0.2 92 75 2
M16 Presecamine 676.897 0 8 7.5 −5.7 −7.1 134.1 0 83 79 2
M17 Sewarine 338.405 1 4 3.3 −4.1 −5.3 305.7 0 91 69 0
M18 Stemmadenine 354.448 0 5 3.3 −3.4 −5.2 363.8 0 92 57 0
M19 Strictamine 322.406 0 6 2.4 −2.3 −4.7 624.1 0.4 91 47 0
M20 Strictosamide 498.532 5 15 0.6 −4 −5.9 94.5 −2.1 66 147 0
M21 Strictosidine 530.574 6 15 0.5 −2.6 −6.4 34.7 −1.7 19 164 3
M22 Taberonine 336.433 0 3 4 −4.1 −5.3 617.2 0.3 100 51 0
M23 Tetrahydrlstonine 352.432 1 6 3.2 −4.3 −6.1 573.5 0.3 95 59 0
M24 Vallesiachotamine 350.416 1 6 3.4 −5 −5.1 932 −0.6 100 81 0
M25 Aspidospermoise 428.527 3 12 0.2 −1.3 −5.9 16.8 −0.4 50 102 0
M26 Bhimbrine 354.448 1 5 3.6 −3.9 −5.5 370.7 −0.1 94 69 0
M27 Bhimbrine N-oxide 370.447 1 6 3.7 −3.2 −5.1 917.7 −0.7 100 79 0
M28 Rhazimine 350.416 0 8 2.4 −3.5 −6.7 333.6 0 86 67 0
M29 Rhazimanine 354.448 1 5 3.7 −4.6 −6.1 305.6 −0.2 93 71 0
M30 Rhazicine 368.432 0 7 1.6 −1 −5.5 56.9 0.3 68 88 0
M31 Leepacine 350.416 1 7 1.6 −1.7 −5.9 103.1 0.6 72 74 0
M32 2-Methoxy 1-2,dihydrorhazamine 382.458 0 8 1.8 −1.1 −5.7 113.2 0.6 74 72 0
M33 HR-1 370.447 1 6 3.8 −3.3 −5 1346.8 −0.5 100 70 0
M34 Vincanicine 322.406 0 4 3.1 −3.1 −4.7 454.4 0.2 93 62 0
M35 Rhazinaline 350.416 0 8 1.5 −1.3 −4.7 337 0.1 81 68 0
M36 beta-Sitosterol 414.713 1 2 7.5 −8.2 −4.4 4119.2 −0.2 100 21 1
M37 Ursolic acid 456.707 2 4 6.1 −6.8 −1.7 304.5 −0.4 94 60 1
M38 Stigmasterol 412.698 1 2 7.4 −8.1 −4.3 4119.2 −0.2 100 21 1
M39 Olenaolic acid 456.707 2 4 6.2 −7 −1.8 306 −0.4 95 60 1
M40 Rhazidigenine (rhazidine) 298.427 1 4 3.1 −3.1 −4.8 849.1 0.4 100 34 0
M41 N-methylleuconolam 340.421 1 7 2.4 −3.4 −3.8 1336.6 −0.3 100 66 0
M42 (+)-Quebranchamine 282.428 1 2 4.1 −4 −5 1678.5 0.7 100 15 0
M43 Polyneuridine 350.416 1 6 2.4 −3.1 −5 299.1 0 85 75 0
M44 (+)-Vincadiformine 338.449 0 3 4.1 −4.3 −5.2 655.8 0.3 100 49 0
M45 (−)-Vincadiformine 338.449 0 3 4.1 −4.3 −5.2 713 0.3 100 49 0
M46 Secamine 676.897 0 7 8.6 −8.3 −8.5 200.4 0.2 92 76 2
M47 Vincadine 340.464 0 3 4.6 −5.4 −6 637.6 0.2 100 46 0
M48 Bis-strictidine 560.824 2 3 7.9 −7.7 −5.8 1941.9 0.7 100 24 2
M51 Rhazisidine 614.829 1 5 8.8 −9.3 −7.6 1208.3 0.2 100 50 2
M52 Isorhazicine 368.432 0 7 1.6 −1.1 −5.7 49 0.2 66 88 0
M53 Rhazigine 618.861 1 5 8.9 −9.2 −8.6 153.6 0.1 92 65 2
M54 Strictisidine 348.401 0 8 1.5 −1.7 −5.1 270.9 0 79 74 0
M55 Strictamine-N-oxide 338.405 0 7 2.3 −0.9 −3.8 1371.3 −0.2 97 58 0
M56 Strictigine 278.396 0 4 3.1 −2.5 −4.7 1380.1 0.6 100 19 0
M57 Strictine 336.39 0 6 3.1 −3.3 −4.1 2156.2 −0.2 100 59 0
M58 Stricticine 338.405 0 5 2.9 −2.8 −4.9 836.2 0.5 96 65 0
M59 Strictalamine 292.38 0 6 1.6 −1.7 −4.7 602.9 0.4 86 50 0
M60 1,2-Dehydro-aspido-spermine 280.412 0 4 3.2 −2.7 −4.6 1558 0.7 100 15 0
M61 Tetrahydrosecodine 342.48 0 3 5 −5.1 −5.9 687.8 0 100 50 0
M62 Dihydrosecodine 340.464 0 3 5 −5.5 −6.5 632.6 −0.1 100 51 0
M63 Dihydrosecamine 678.913 0 7 8.6 −8 −8.1 214.4 0.2 93 75 2
M64 Dihydropresecamine 678.913 0 8 7.8 −6 −7 155.8 0.1 86 78 2
M65 Tetrahydropresecamine 680.929 0 8 7.8 −6.5 −7.3 144.9 0 85 80 2
M66 Rhazinol 294.396 1 5 1.2 −1.8 −4.6 581 0.3 83 40 0
M67 Rhazimol 352.432 0 6 2.4 −2 −4.8 572.5 0.2 90 60 0
M68 Rhazidigenine-N-oxide 314.427 1 5 3.1 −1.9 −4 1964.2 −0.2 100 46 0
M69 (−)-16R,21R-Omethyleburmanine 310.438 0 4 3.3 −3.3 −4.9 2470.6 −0.7 100 13 0
M70 Decarbomethoxy-15,20,16,17-tetrahydrosecodine 284.444 1 2 4.7 −4.6 −5.8 1672.7 0.5 100 18 0
M71 1,2-Dehydro-aspidospermidine-N-oxide 296.411 0 5 3.1 −1.2 −3.5 4109.3 0.2 100 29 0
M72 Rhazizine 368.432 0 7 2.5 −2.1 −4.5 1005.1 0.6 95 53 0
M73 15-Hydroxy-vincadifformine 354.448 1 5 3.2 −3.8 −5.3 302.4 −0.1 90 67 0
M74 Dihydroburnamenine 280.412 0 2 3.9 −3.6 −4.8 2470.6 0 100 5 0
M75 16s,16’-Decarboxy-tetrahydrosecamine 622.892 1 6 7.6 −6.1 −6.8 295.2 0.5 90 45 2
M76 Nor-C-fluorocuraine 292.38 0 3 2.8 −2.3 −3.8 512 0.4 92 52 0
M77 Strictibine 213.235 1 2 2.5 −3.3 −4.7 1789.3 −0.2 100 49 0

MW molecular weight, HBD hydrogen bond donors, HBA hydrogen bond acceptors, QPlogP predicted octanol/water partition coefficient, QPlogS predicted aqueous solubility, QPlogHERG predicted IC50 value for blockage of HERG K+ channels, QPCaco2 predicted Caco-2 cell permeability, QPlogBB predicted brain/blood partition coefficient, %HOA percentage of human oral absorption, PSA polar surface area, RO5v number of violations of Lipinski’s Rule of Five

Table 6.

Surface related and ring-related properties of Rhazya stricta compounds

ID Name CR NR NOR HetR #R Para Ind.Ref Sur.Ten Density Polar.
1 Akuammidine 0.81 0.08 0.19 0.19 6 743.43 1.68 65.34 1.35 39.32
2 Antirhine 0.86 0.09 0.14 0.14 4 676.25 1.65 56.53 1.2 35.76
3 3-Epi-antirhine 0.86 0.09 0.14 0.14 4 676.25 1.65 56.53 1.2 35.76
4 Aspidosespermidine 0.9 0.1 0.1 0.1 5 647.87 1.63 50.04 1.16 34.2
5 Condylocarpine 0.83 0.08 0.17 0.17 5 681.18 1.66 56.36 1.3 36.43
6 Dihydrocorynantheol 0.86 0.09 0.14 0.14 4 687.1 1.64 55.86 1.19 35.85
7 Eburnamenine 0.9 0.1 0.1 0.1 5 589.57 1.7 49.78 1.25 33.94
8 Eburnamine 0.86 0.09 0.14 0.14 5 595.24 1.72 54.34 1.35 34.28
9 Eburnamonine 0.86 0.09 0.14 0.14 5 595.24 1.72 54.34 1.34 34.28
10 Geissoschizine 0.81 0.08 0.19 0.19 4 762.54 1.66 61.38 1.29 40.01
11 Isositsirikine 0.81 0.08 0.19 0.19 4 776.63 1.64 59.3 1.27 40.13
12 16-Epi-Z-isositsirikine 0.81 0.08 0.19 0.19 4 776.63 1.64 59.3 1.27 40.13
13 Leuconolam 0.79 0.08 0.21 0.21 4 692.66 1.65 63.34 1.33 35.61
14 Rhazinilam 0.86 0.09 0.14 0.14 4 635.67 1.65 47.86 1.22 34.93
15 Tetrahydrosecamine 0.84 0.08 0.16 0.16 7 1449.04 1.63 46.81 1.23 78.28
16 Presecamine 0.84 0.08 0.16 0.16 7 1516.34 1.65 60.13 1.24 78.73
17 Sewarine 0.8 0.08 0.2 0.2 5 696.4 1.69 64.76 1.38 37.04
18 Stemmadenine 0.81 0.08 0.19 0.19 5 729.69 1.64 47.88 1.28 39.55
19 Strictamine 0.83 0.08 0.17 0.17 5 631.14 1.71 52.17 1.37 36.23
20 Strictosamide 0.72 0.06 0.28 0.28 6 986.67 1.72 84.28 1.53 50.75
21 Strictosidine 0.71 0.05 0.29 0.29 5 1078.5 1.66 74.07 1.44 54
22 Tabersonine 0.84 0.08 0.16 0.16 5 723.31 1.65 55.72 1.27 38.37
23 Tetrahydroalstonine 0.81 0.08 0.19 0.19 5 748.43 1.66 58.69 1.3 39.39
24 Vallesiachotamine 0.81 0.08 0.19 0.19 4 754.43 1.65 59.07 1.29 39.54
25 Aspidospermiose 0.77 0.06 0.23 0.23 6 885.22 1.68 74 1.42 45.19
26 Bhimberine 0.81 0.08 0.19 0.19 4 776.63 1.64 59.3 1.27 40.13
27 Bhimbhrine N-oxide 0.78 0.07 0.22 0.22 4  45.12
28 Rhazimine 0.81 0.08 0.19 0.19 6 690.3 1.69 54.96 1.38 38.6
29 Rhazimanine 0.81 0.08 0.19 0.19 4 776.63 1.64 59.3 1.27 40.13
30 Rhazicine 0.78 0.07 0.22 0.22 6 757.54 1.66 64.83 1.38 39.13
31 Leepacine 0.81 0.08 0.19 0.19 7 709 1.68 63.18 1.39 37.7
32 2-Methoxy-1,2-dihydrorhazimine 0.79 0.07 0.21 0.21 6 800.93 1.63 56.72 1.31 41.05
33 HR-1 0.78 0.07 0.22 0.22 4
34 Vincanicine 0.83 0.08 0.17 0.17 5 683.12 1.66 57.29 1.3 36.52
35 Rhazinaline 0.81 0.08 0.19 0.19 5 690.3 1.69 54.96 1.38 38.6
36 Beta-sitosterol 0.97 0 0.03 0.03 4 1051.02 1.52 37.64 0.98 51.22
37 Ursolic acid 0.91 0 0.09 0.09 5 1076.71 1.56 45 1.1 52.93
38 Stigmasterol 0.97 0 0.03 0.03 4 1038.63 1.53 38.25 0.99 51.19
39 Oleanolic acid 0.91 0 0.09 0.09 5 1077.07 1.56 45.41 1.1 52.95
40 Rhazidigenine 0.86 0.09 0.14 0.14 4 650.55 1.64 48.09 1.21 35.15
41 N-methylleuconolam 0.8 0.08 0.2 0.2 4 730.79 1.65 61.9 1.31 37.53
42 (+)-Quebrachamine 0.9 0.1 0.1 0.1 4 672.49 1.62 50.29 1.12 35.27
43 Polyneuridine 0.81 0.08 0.19 0.19 6 735.31 1.67 62.83 1.34 38.85
44 (+)-Vincadiformine 0.84 0.08 0.16 0.16 5 735.7 1.63 53.98 1.25 38.4
45 (-)-Vincadifformine 0.84 0.08 0.16 0.16 5 735.7 1.63 53.98 1.25 38.4
46 Secamine 0.84 0.08 0.16 0.16 7 1449.04 1.63 46.81 1.22 78.28
47 Vincadine 0.84 0.08 0.16 0.16 4 776.11 1.61 52.34 1.18 39.67
48 Bis-strictidine 0.9 0.1 0.1 0.1 9 1150.88 1.73 52.95 1.31 67.18
49 3,14-Dehydrorhazigine 0.87 0.09 0.13 0.13 7 1340.13 1.64 46.53 1.2 73.46
50 16-Hydrorhazisidine 0.85 0.09 0.15 0.15 7 1345.28 1.65 48.02 1.24 73.94
51 Rhazisidine 0.87 0.09 0.13 0.13 8 1284.82 1.68 49.12 1.27 72.59
52 Isorhazicine 0.78 0.07 0.22 0.22 6 757.54 1.66 64.83 1.38 39.13
53 Rhazigine 0.87 0.09 0.13 0.13 7 1412.62 1.65 58.36 1.21 74.23
54 Strictisidine 0.81 0.08 0.19 0.19 7 635.5 1.78 63.63 1.55 37.59
55 Strictamine-N-oxide 0.8 0.08 0.2 0.2 5
56 Strictigine 0.9 0.1 0.1 0.1 5 622.49 1.63 42.69 1.14 34.52
57 Strictine 0.8 0.08 0.2 0.2 5 636.29 1.73 55.79 1.44 36.71
58 Stricticine 0.8 0.08 0.2 0.2 6 682.41 1.68 61.46 1.39 36.43
59 Strictalamine 0.86 0.09 0.14 0.14 5 580.88 1.74 55.15 1.37 33.92
60 1,2-Dehydroaspidospermidine 0.9 0.1 0.1 0.1 5 590.09 1.7 50.6 1.27 33.8
61 Tetrahydrosecodine 0.84 0.08 0.16 0.16 3 807.26 1.56 42.67 1.08 40.69
62 Dihydrosecodine 0.84 0.08 0.16 0.16 3 793.18 1.58 44.47 1.11 40.53
63 Dihydrosecamine 0.84 0.08 0.16 0.16 7 1449.04 1.63 46.81 1.23 78.28
64 Dihydropresecamine 0.84 0.08 0.16 0.16 7 1530.43 1.64 59.1 1.23 78.84
65 Tetrahydropresecamine 0.84 0.08 0.16 0.16 7 1544.52 1.63 58.11 1.22 78.96
66 Rhazinol 0.86 0.09 0.14 0.14 5 580.88 1.74 55.15 1.38 33.92
67 Rhazimol 0.81 0.08 0.19 0.19 5 690.3 1.69 54.96 1.39 38.6
68 Rhazidigenine-N-oxide 0.83 0.09 0.17 0.17 4
69 (-)16R,21R-omethyleburnamine 0.87 0.09 0.13 0.13 5 639.83 1.67 47.55 1.27 36.25
70 Decarbomethoxy-15,20,16,17-tetrahydros 0.9 0.1 0.1 0.1 3 703.65 1.57 40.68 1.02 36.31
71 1-2-Dehydroasidospermidine-N-oxide 0.86 0.09 0.14 0.14 5
72 Rhazizine 0.78 0.07 0.22 0.22 6 744.62 1.67 62.43 1.39 39.14
73 15-Hydroxyvincadifformine 0.81 0.08 0.19 0.19 5 750.68 1.65 60.33 1.32 39
74 Dihydroeburnamenine 0.9 0.1 0.1 0.1 5 589.57 1.7 49.78 1.26 33.94
75 16s,16′-Decarboxytetra-hydrosecamine 0.87 0.09 0.13 0.13 7 1339.61 1.64 46.2 1.21 73.6
76 Nor-C-fluorocurarine 0.86 0.09 0.14 0.14 5 624.5 1.68 57.83 1.29 33.99
77 Strictibine 0.81 0.06 0.19 0.19 3 442.8 1.65 51.74 1.29 23.76

Ind Ref refractive index, Para parachor, Sur ten surface tension, Polar polarizability, #R number of rings, CR ratio of carbons, NR ratio of nitrogens, NOR ratio of oxygens, HetR ratio of heteroatoms

Predicted therapeutic area applications

PASS—prediction of activity spectra for substances

This web-based predictive server from Way2Drug, has variety of annotators of substances for their probability of active or inactive towards few targets. Out of all services and products of them, we utilized PASS method of predictions. More than 100 activities are predicted with their probability of activities and in-activities. Some of them include kinase inhibitors, GPCR antagonists, and some specific targets like adrenergic receptors, and their kinase inhibitors. We considered the probability of active (Pa) >0.3 (i.e. >30%), and should be greater than probability of inactive (Pi). Given these conditions, we observed many alkaloids have indicated Pa >0.8 in certain conditions (such as, anthrine has predicted Pa at 90% towards β-adrenergic receptor kinase inhibitor, 5-HTA release stimulant). Majority of them also is predicted to be substrate to CYP3A4 and CYP2D6 indicating their metabolic instability (Pa ~ 0.5, 0.4, respectively). Several such predictions for all 78 alkaloids has been computed—leaving predictions to be validated, experimentally. Similarly, dihydrocorynantheol and corynantheol were also predicted to be 5-HT release stimulants, and have been projected to be chemosensitizers. Eburnamenine is predicted to be a Nootropic agent at 90% Pa, while eburnamine is predicted to be a CNS (anti-depressant and mood disorder management agent at >96% Pa). Strictosidine is predicted to be an antiprotozoal at 86% Pa, β-sitosterol is anti-hypercholesterolemic agent with Pa ~98%, rhazidigenine (rhazidine) is an antidyskinetic at 60% Pa, secamine is a H1F1A expression inhibitor at 83% Pa (but a non-pharmaceutically acceptable molecule due to high MW and many RO5 violations). A similar observations is also made for 16-hydrorhazisidine (72% Pa for H1F1A expression inhibitor). Strictamine is predicted to be gluconate 2-dehydrogenase acceptor with 70% Pa, and 1,2-dehydroaspidospermine (which is a small molecule) has been predicted to be analeptic with 77% Pa. Dihydrosecamine is predicted to be a H1F1A expression inhibitor with 77% Pa, and rhazidigenine-N-oxide is predicted to be a cognition disorder agent with 64% Pa. Decarbomethoxy-15,20,16,17-tetrahydrosecodine is a small molecule with ~70% Pa for antidyskinetic and antineuronic agent, 1,2-dehydrospidospermidine-N-oxide is predicted to be 87% as analeptic.

Anticancer activity through CDRUG

This set of predictions using the structures and SMILES codes of the alkaloids, annotates the anti-cancer activity by predicting “Mean logGI50”. Most molecules that have Mean LogGI50 values lower than −5 are considered to have anti-cancer activity. It is interesting to know that all the molecules of R. stricta alkaloids (indole/non-indole) have predicted mean logGI50 values ranging between −4.95 and −6.50—indicating they all may have anti-cancer activities. There are about 10 compounds that have predicted logGI50 values less than −6, which indicate strong anti-cancer activity. Table 7 shows the predicted mean LogGI50 values of all the compounds considered in the present study.

Table 7.

Predicted mean LogGI50 of Rhazya stricta compounds whose values lower than −6.0 are highlighted in italics may exhibit anti-cancer activity

MOL ID Name Mean LogGI50 CDRUG
M1 Akummidine −5.408
M2 Antirhine −5.408
M3 3-Epi-antirhine −5.408
M4 Aspidosespermidine −5.726
M5 Condylocarpine −5.726
M6 Dihydrocorynantheol −5.408
M7 Eburnamenine −5.096
M8 Eburnamine −5.096
M9 Eburnamonine −5.096
M10 Geissoschizine −5.048
M11 Isositsirikine −5.408
M12 16-Epi-Z-isositsirikine −5.408
M13 Leuconalm −5.154
M14 Rhazinliam −5.096
M15 Tetrahydrosecamine −4.975
M16 Presecamine −5.726
M17 Sewarine −5.726
M18 Stemmadenine −5.408
M19 Strictamine −5.726
M20 Strictosamide −5.256
M21 Strictosidine −5.937
M22 Taberonine −5.726
M23 Tetrahydrlstonine −5.408
M24 Vallesiachotamine −5.408
M25 Aspidospermoise −5.726
M26 Bhimbrine −5.408
M27 Bhimbrine N-oxide −5.408
M28 Rhazimine −5.726
M29 Rhazimanine −5.408
M30 Rhazicine −5.726
M31 Leepacine −5.726
M32 2-Methoxy 1-2,dihydrorhazamine −5.726
M33 HR-1 −5.096
M34 Vincanicine −5.726
M35 Rhazinaline −5.726
M36 Beta-sitosterol −5.918
M37 Ursolic acid −5.124
M38 Stigmasterol −5.918
M39 Olenaolic acid −5.124
M40 Rhazidigenine (rhazidine) 6.327
M41 N-methylleuconolam −5.154
M42 (+)-Quebranchamine −5.861
M43 Polyneuridine −5.408
M44 (+)-Vincadiformine −5.726
M45 (−)-Vincadiformine −5.726
M46 Secamine 6.298
M47 Vincadine −5.486
M48 Bis-strictidine −5.409
M49 3,14-Dehydrorhazigine −5.726
M50 16-Hydrorhazisidine 6.298
M51 Rhazisidine −5.406
M52 Isorhazicine −5.726
M53 Rhazigine −5.726
M54 Strictisidine −5.726
M55 Strictamine-N-oxide −5.726
M56 Strictigine −5.726
M57 Strictine −5.096
M58 Stricticine −5.726
M59 Strictalamine 6.327
M60 1,2-Dehydroaspidospermine 6.327
M61 Tetrahydrosecodine −5.783
M62 Dihydrosecodine −5.408
M63 Dihydrosecamine 6.298
M64 Dihydropresecamine −5.726
M65 Tetrahydropresecamine −5.726
M66 Rhazinol −5.726
M67 Rhazimol −5.726
M68 Rhazidigenine-N-oxide 6.327
M69 (−)-16R,21R-Omethyleburmanine −5.096
M70 Decarbomethoxy-15,20,16,17-tetrahydrosecodine 6.471
M71 1,2-Dehydroaspidospermidine-N-oxide 6.327
M72 Rhazizine −4.878
M73 15-Hydroxyvincadifformine −5.726
M74 Dihydroburnamenine −5.096
M75 16s,16′-Decarboxytetrahydrosecamine −4.975
M76 Nor-C-fluorocuraine −5.726
M77 Strictibine −5.785

SuperPred—predicted target interactions

From this server studies on R. stricta alkaloids, we observed that many of these molecules may interact with CYP2D6 or CYP3A4 as substrates. The indication of these results mean that their target may be unknown, but they do modify the drug metabolism, and affect drug–drug interactions.

SwissTarget prediction

While predictions from this web-server may suggest each molecule have certain target activity, they almost correlate well with the PASS server prediction—which gives additional probability of prediction for each molecule to be active or inactive against the target of interest.

Overall from the calculated cheminformatics studies and web-server predictions, we understand that few molecules like anthrine, condylocarpine, dihydrocorynantheol etc. have predicted GIC50 values in sub µM concentrations, while they also have predicted drug–drug activity towards CYP3A4, and CYP2D6 enzymes. Most molecules turnout to be modulators of membrane receptor ligands while some have predicted cholinesterase, CNS (5HT2x), adenosine (A2A/A2B) activity. Moreover, all molecules have predicted activity towards certain targets (Pa > 30%).

Conclusions

Table 8 indicates the top 10-best naturally occurring indole alkaloids of R. stricta that were predicted to be having decent anti-cancer activity and other good physiochemical properties together with cheminformatics properties—these molecules are antirhine, 3-epi-antirhine, condylocarpine, eburnamine, eburnamonine, taberonine, ursolic acid, stigmasterol, olenaolic acid, (+)-vincadiformine, (−)-vincadiformine, (−)-16R,21R-omethyleburmanine, 15-hydroxy-vincadifformine, and dihydroburnamenine.

Table 8.

Key details of top molecules with predicted targets for anti-cancer and anti-obesity, probable rule-of-5, predicted LogGI50 with predicted H-, and p values

SI. No Mol. name Mol. wt Predicted
LogG150/H-/p val Target RO5 violations Liability Comment
Anti-cancer Anti-obesity Druggability Hepatic HERG, renal issues
M2 Antirhine 296.411 −5.41/0.39/0.05 5HT2A,BC Good CYP2D6 None predicted
M3 3-Epi-antirhine 296.411 −5.41/0.39/0.05 5HT2A,B Good CYP2D6 None predicted
M5 Condylocarpine 322.406 −5.73/0.42/0.03 Negative Good None None predicted
M8 Eburnamine 296.411 −5.10/0.74/0.01 5HT2A,BC Good 2D6,3A4 None predicted
M9 Eburnamonine 294.396 −5.10/1.00/0.01 5HT2A,BC Good 2D6,3A4 None predicted
M22 Taberonine 336.433 −5.73/0.67/0.01 Negative Good None None predicted
M37 Ursolic acid 456.707 −5.12/1.00/0.00 Negative Moderate (LogP) None Highly hydrophobic
M38 Stigmasterol 412.698 −5.92/0.93/0.04 Negative Moderate (LogP) CYP17A1 Highly hydrophobic
M39 Olenaolic acid 456.707 −5.12/0.71/0.07 Negative Moderate (LogP) None Highly hydrophobic
M44 (+)-Vincadiformine 338.449 −5.73/0.56/0.02 5HT3A Good None None predicted
M45 (−)-Vincadiformine 338.449 −5.73/0.56/0.02 5HT3A Good None None predicted
M69 (−)-16R,21R-Omethyleburma nine 310.438 −5.10/0.55/0.02 5HT2A,BC Good CYP2D6 None predicted
M73 15-Hydroxy-vincadifformine 354.448 −5.73/0.56/0.02 5HT2A,BC Good None None predicted
M74 Dihydroburnamenine 280.412 −5.10/0.63/0.01 Negative Good 2D6,3A4 None predicted

Authors’ contribution

AYO, SV, RSB were involved in generation of computational data on predictive properties of various Rhazya stricta’s alkaloids; NHH and AMSO participated in data acquisition. SV, JSMS and KSS were involved in overall research planning & supervision, data analysis and manuscript writing. All authors read and approved the final manuscript.

Acknowledgements

The authors gratefully acknowledge the financial support from KAU Vice President for Educational Affairs Prof. Dr. Abdulrahman O Alyoubi, The Deanship of Scientific Research (DSR) at King Abdulaziz University (KAU), Jeddah, Saudi Arabia, represented by the Unit of Strategic Technologies Research through the Project number (D 008/431) for the Project entitled: “Identification and Isolation of Salt and Heat-Tolerance Genes of R. stricta and Detection of Metabolites and their Therapeutic Effects via Cheminformatics”.

Competing interests

The authors declare that they have no competing interests.

Contributor Information

Abdullah Y. Obaid, Email: aobaid@kau.edu.sa

Sreedhara Voleti, Email: sreedhara.voleti@gmail.com.

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Kulvinder Singh Saini, Email: ksaini@kau.edu.sa.

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