In-silico Studies and Wet-Lab Validation of Camptothecin Derivatives for Anti-Cancer Activity Against Liver (HepG2) and Lung (A549) Cancer Cell Lines.

BACKGROUND: In the present study, we have explored the utility of QSAR modelling, in silico ADMET, docking, chemical semi-synthesis, and in vitro evaluation studies for the identification of active camptothecin (CPT) derivatives against cancer-targeting human liver (HepG2) and lung (A549) cancer cell lines. METHODS: Two QSAR models were developed as screenings tools using the multiple linear regression (MLR) method followed by ADMET and docking studies. The regression coefficient (r2) and cross-validation regression coefficients (rCV2T) of the QSAR model for the HepG2 cell line was 0.95 and 0.90, respectively, and for the A549 cell line, it was 0.93 and 0.81, respectively. RESULTS: In silico studies show that CPT derivatives (CPT-1 and CPT-6) possess drug-like properties. Docking performed on DNA Topoisomerase-I showed significant binding affinity. Finally, predicted active derivatives were chemically semi synthesized, spectroscopically characterized, and evaluated in-vitro for cytotoxic/anticancer activity against HepG2 and A549 cell lines. CONCLUSION: The experimental results are consistent with the predicted results. These findings may be of immense importance in the anticancer drug development from an inexpensive and widely available natural product, camptothecin.

Anti-tubercular agents from Glycyrrhiza glabra.

Bioactivity guided isolation of Glycyrrhiza glabra (Leguminosae / Fabaceae) roots resulted in the characterization of 18ß-glycyrrhetinic acid as a major anti-tubercular agent. Further, GA-1 was semi-synthetically converted into its nine derivatives, which were in-vitro evaluated for their antitubercular potential against Mycobacterium tuberculosis H37Rv using BACTEC-460 radiometric susceptibility assay. All the derivatives were active, but the benzylamide (GA-8, MIC 12.5µg/ml) and ethyl oxylate (GA-3, MIC 25.0 µg/ml) derivatives were significantly active against the pathogen. This was further supported by the molecular docking studies, which showed adequate docking (LibDock) scores for GA-3 (120.3) and GA-8 (112.6) with respect to the standard anti-tubercular drug, rifampicin (92.94) on the DNA-directed RNA polymerase subunit beta (rpoB) target site. Finally, the in silico pharmacokinetic and drug-likeness studies showed that GA-3 and GA- 8 possesses drug-like properties. This is the first ever report on the anti-tubercular potential of GA and its derivatives. These results may be of great help in anti-tubercular drug development from a very common, inexpensive, and non toxic natural product.

Epigenetic impact of curcumin on stroke prevention.

The epigenetic impact of curcumin in stroke and neurodegenerative disorders is curiosity-arousing. It is derived from Curcuma longa (spice), possesses anti-oxidative, anti-inflammatory, anti-lipidemic, neuro-protective and recently shown to exhibit epigenetic modulatory properties. Epigenetic studies include DNA methylation, histone modifications and RNA-based mechanisms which regulate gene expression without altering nucleotide sequences. Curcumin has been shown to affect cancer by altering epigenetic changes but its role as an epigenetic agent in cerebral stroke has not been much explored. Although curcumin possesses remarkable medicinal properties, the bioavailability of curcumin has limited its success in epigenetic studies and clinical trials. The present review is therefore designed to look into epigenetic mechanisms that could be induced with curcumin during stroke, along with its molecular designing with different moieties that may increase its bioavailability. Curcumin has been shown to be encapsulated in exosomes, nano-vesicles (<200 nm), thereby showing its therapeutic effects in brain diseases. Curcumin delivered through nanoparticles has been shown to be neuroregenerative but the use of nanoparticles in brain has limitations. Hence, curcumin-encapsulated exosomes along with curcumin-primed exosomes (exosomes released by curcumin-treated cells) are much needed to be explored to broadly look into their use as a novel therapy for stroke.

In vitro, in silico and in vivo studies of ursolic acid as an anti-filarial agent.

As part of our drug discovery program for anti-filarial agents from Indian medicinal plants, leaves of Eucalyptus tereticornis were chemically investigated, which resulted in the isolation and characterization of an anti-filarial agent, ursolic acid (UA) as a major constituent. Antifilarial activity of UA against the human lymphatic filarial parasite Brugia malayi using in vitro and in vivo assays, and in silico docking search on glutathione-s-transferase (GST) parasitic enzyme were carried out. The UA was lethal to microfilariae (mf; LC100: 50; IC50: 8.84 µM) and female adult worms (LC100: 100; IC50: 35.36 µM) as observed by motility assay; it exerted 86% inhibition in MTT reduction potential of the adult parasites. The selectivity index (SI) of UA for the parasites was found safe. This was supported by the molecular docking studies, which showed adequate docking (LibDock) scores for UA (-8.6) with respect to the standard antifilarial drugs, ivermectin (IVM -8.4) and diethylcarbamazine (DEC-C -4.6) on glutathione-s-transferase enzyme. Further, in silico pharmacokinetic and drug-likeness studies showed that UA possesses drug-like properties. Furthermore, UA was evaluated in vivo in B. malayi-M. coucha model (natural infection), which showed 54% macrofilaricidal activity, 56% female worm sterility and almost unchanged microfilaraemia maintained throughout observation period with no adverse effect on the host. Thus, in conclusion in vitro, in silico and in vivo results indicate that UA is a promising, inexpensive, widely available natural lead, which can be designed and developed into a macrofilaricidal drug. To the best of our knowledge this is the first ever report on the anti-filarial potential of UA from E. tereticornis, which is in full agreement with the Thomson Reuter's 'Metadrug' tool screening predictions.

QSAR and docking studies on capsazepine derivatives for immunomodulatory and anti-inflammatory activity.

Capsazepine, an antagonist of capsaicin, is discovered by the structure and activity relationship. In previous studies it has been found that capsazepine has potency for immunomodulation and anti-inflammatory activity and emerging as a favourable target in quest for efficacious and safe anti-inflammatory drug. Thus, a 2D quantitative structural activity relationship (QSAR) model against target tumor necrosis factor-α (TNF-α) was developed using multiple linear regression method (MLR) with good internal prediction (r2 = 0.8779) and external prediction (r2pred = 0.5865) using Discovery Studio v3.5 (Accelrys, USA). The predicted activity was further validated by in vitro experiment. Capsazepine was tested in lipopolysaccharide (LPS) induced inflammation in peritoneal mouse macrophages. Anti-inflammatory profile of capsazepine was assessed by its potency to inhibit the production of inflammatory mediator TNF-α. The in vitro experiment indicated that capsazepine is an efficient anti-inflammatory agent. Since, the developed QSAR model showed significant correlations between chemical structure and anti-inflammatory activity, it was successfully applied in the screening of forty-four virtual derivatives of capsazepine, which finally afforded six potent derivatives, CPZ-29, CPZ-30, CPZ-33, CPZ-34, CPZ-35 and CPZ-36. To gain more insights into the molecular mechanism of action of capsazepine and its derivatives, molecular docking and in silico absorption, distribution, metabolism, excretion and toxicity (ADMET) studies were performed. The results of QSAR, molecular docking, in silico ADMET screening and in vitro experimental studies provide guideline and mechanistic scope for the identification of more potent anti-inflammatory & immunomodulatory drug.

In silico and in vivo anti-malarial studies of 18ß glycyrrhetinic acid from Glycyrrhiza glabra.

Malaria is one of the most prevailing fatal diseases causing between 1.2 and 2.7 million deaths all over the world each year. Further, development of resistance against the frontline anti-malarial drugs has created an alarming situation, which requires intensive drug discovery to develop new, more effective, affordable and accessible anti-malarial agents possessing novel modes of action. Over the past few years triterpenoids from higher plants have shown a wide range of anti-malarial activities. As a part of our drug discovery program for anti-malarial agents from Indian medicinal plants, roots of Glycyrrhizaglabra were chemically investigated, which resulted in the isolation and characterization of 18ß-glycyrrhetinic acid (GA) as a major constituent. The in vitro studies against P. falciparum showed significant (IC50 1.69 µg/ml) anti-malarial potential for GA. Similarly, the molecular docking studies showed adequate docking (LibDock) score of 71.18 for GA and 131.15 for standard anti-malarial drug chloroquine. Further, in silico pharmacokinetic and drug-likeness studies showed that GA possesses drug-like properties. Finally, in vivo evaluation showed a dose dependent anti-malarial activity ranging from 68-100% at doses of 62.5-250 mg/kg on day 8. To the best of our knowledge this is the first ever report on the anti-malarial potential of GA. Further work on optimization of the anti-malarial lead is under progress.

Glycyrrhetinic acid and its analogs: a new class of antifilarial agents.

Although a number of chemicals have been isolated from Glycyrrhiza glabra, only a few have been evaluated for their biological significance. As part of our drug discovery program for antifilarial agents from Indian medicinal plants, the roots of G. glabra were chemically investigated, which resulted in the isolation and characterization of an antifilarial agent, glycyrrhetinic acid (GA, 1a) effective against microfilariae (mf) in vitro (LC100: 12.5 µM; IC50: 1.20 µM), but was inactive against adult worms. Further, GA (1a) was converted into six analogs (2a-7a) and their antifilarial potential was evaluated by studying in vitro motility and MTT reduction assays employing mf and adult worms of Brugia malayi. The results showed that out of six GA analogs, the benzyl amide analog (6a) killed adults and mf at 25 and 50 µM concentration, respectively, and inhibited 49% MTT reduction potential of the adult parasites. The IC50 values were found to be 8.8 and 2.2 µM for adults and mf, respectively. The SI of the compound was >60. On the other hand the octylamide analog (7a) required much higher concentration to adversely affect the parasites. Finally, both active amide analogs (6a and 7a) were in vivo evaluated using B. malayi-jird model, which showed that analog 6a possesses promising macrofilaricidal activity at 100mg/kg, s.c. ×5 days and around 40% of the treated animals showed calcified masses of worm fragments in peritoneal cavity of the animals. To the best of our knowledge this is the first ever report on the antifilarial potential of GA analogs. Further work on optimization of the antifilarial lead is under progress.

Cytotoxic evaluation of semisynthetic ester and amide derivatives of oleanolic acid.

Although a number of chemicals have been isolated from Lantana camara, only a few have been evaluated for their biological significance. As part of our drug discovery program for cytotoxic agents from Indian medicinal plants, roots of L. camara L. were chemically investigated, which resulted in the isolation and identification of a cytotoxic agent, oleanolic acid (1b) as a major constituent. Oleanolic acid was converted into six semi-synthetic ester (2-7) and seven amide (8-14) derivatives. The ester derivatives (2-7) showed 3-6 times more selective activity than 1b against the human ovarian cancer cell line (IGR-OV-1), while amide derivatives 8-14 showed 16-53 times more selective activity against the human lung cancer cell line (HOP-62). Structure activity relationship within the ester (2-7) and amide (8-14) derivatives are discussed.