The Bioactive Potential of Culturable Fungal Endophytes Isolated From the Leaf of Catharanthus roseus (L.) G. Don.

INTRODUCTION: Endophyte is considered a source of natural bioactive secondary metabolites that provides an array of bioactive lead compounds. The present study was aimed to determine the antimicrobial and anti-inflammatory potential of fungal endophytes isolated from Catharanthus roseus. METHODS: A total of seven fungal endophytes crude extract were screened against bacterial pathogens. Of these, Curvularia geniculata CATDLF7 crude extract exhibited the most potent inhibitory activity against bacterial pathogens. Hence, CATDLF7 crude extract was subjected to chromatographic separation. This purification leads to the isolation of six pure compounds (1PS - 6PS). Of these, 3PS was found to be a major constituent and most effective against clinical isolates of methicillin- resistant Staphylococcus aureus (MRSA) with minimum inhibitory concentration (MIC) values ranging from 100 to 200 µg/ml. Based on the spectroscopic data, 3PS was characterized as α,ß- dehydrocurvularin. This compound also showed synergistic interaction with norfloxacin and reduced its MIC up to 32-folds with a fractional inhibitory concentration index (FICI) of 0.09. RESULTS: To understand the possible antibacterial mechanism of action, α,ß-dehydrocurvularin alone (100 µg/ml) exhibited efflux pump inhibitory potential by 0.84 fold decreasing in ethidium bromide (EtBr) fluorescence. In addition, α,ß-dehydrocurvularin inhibited inflammatory cytokines TNF-α and IL-6 production, which is further validated by molecular docking scores -4.921 and -5.641, respectively, for understanding orientation and binding affinity. CONCLUSION: Overall, the results highlighted identifying bioactive compound α,ß-dehydrocurvularin, which could be used as an antimicrobial and anti-inflammatory agent.

2D- and 3D-QSAR modelling, molecular docking and in vitro evaluation studies on 18ß-glycyrrhetinic acid derivatives against triple-negative breast cancer cell line.

Triple-negative breast cancers (TNBCs) are one of the most aggressive and complex forms of cancers in women. TNBCs are commonly known for their complex heterogeneity and poor prognosis. The present work aimed to develop a predictive 2D and 3D quantitative structure-activity relationship (QSAR) models against metastatic TNBC cell line. The 2D-QSAR was based on multiple linear regression analysis and validated by Leave-One-Out (LOO) and external test set prediction approach. QSAR model presented regression coefficient values for training set (r2), LOO-based internal regression (q2) and external test set regression (pred_r2) which are 0.84, 0.82 and 0.75, respectively. Five properties, Epsilon4 (electronegativity), ChiV3cluster (valence molecular connectivity index), chi3chain (retention index for three-membered ring), TNN5 (nitrogen atoms separated through 5 bond distance) and nitrogen counts, were identified as important structural features responsible for anticancer activity of MDA-MB-231 inhibitors. Five novel derivatives of glycyrrhetinic acid (GA) named GA-1, GA-2, GA-3, GA-4 and GA-5 were semi-synthesised and screened through the QSAR model. Further, in vitro activities of the derivatives were analysed against human TNBC cell line, MDA-MB-231. The result showed that GA-1 exhibits improved cytotoxic activity to that of parent compound (GA). Further, atomic property field (APF)-based 3D-QSAR and scoring recognise C-30 carboxylic group of GA-1 as major influential factor for its anticancer activity. The significance of C-30 carboxylic group in GA derivatives was also confirmed by molecular docking study against cancer target glyoxalase-I. Finally, the oral bioavailability and toxicity of GA-1 were assessed by computational ADMET studies.Communicated by Ramaswamy H. Sarma.

In Vitro and In Silico Studies of Glycyrrhetinic Acid Derivatives as Anti- Filarial Agents.

BACKGROUND: Lymphatic filariasis is one of the chronic diseases in many parts of the tropics and sub-tropics of the world despite the use of standard drugs diethylcarbamazine and ivermectin because they kill microfilaries and not the adult parasites. Therefore, new leads with activity on adult parasites are highly desirable. OBJECTIVE: Anti-filarial lead optimization by semi-synthetic modification of glycyrrhetinic acid (GA). METHODS: The GA was first converted into 3-O-acyl derivative, which was further converted into 12 amide derivatives. All these derivatives were assessed for their antifilarial potential by parasite motility assay. The binding affinity of active GA derivatives on trehalose-6-phosphate phosphatase (Bm-TPP) was assessed by molecular docking studies. RESULTS: Among 15 GA derivatives, GAD-2, GAD-3, and GAD-4 were found more potent than the GA and standard drug DEC. These derivatives reduced the motility of Brugia malayi adult worms by up to 74% while the GA and DEC reduced only up to 49%. Further, GA and most of its derivatives exhibited two times more reduction in MTT assay when compared to the standard drug DEC. These derivatives also showed 100% reduction of microfilariae and good interactions with Bm-TPP protein. CONCLUSION: The present study suggests that 3-O-acyl and linear chain amide derivatives of glycyrrhetinic acid may be potent leads against B. malayi microfilariae and adult worms. These results might be helpful in developing QSAR model for optimizing a new class of antifilarial lead from a very common, inexpensive, and non toxic natural product.

Antibiotics potentiating potential of catharanthine against superbug Pseudomonas aeruginosa.

Multidrug resistance (MDR) put an alarming situation like preantibiotic era which compels us to invigorate the basic science of anti-infective chemotherapy. Hence, the drug resistant genes/proteins were explored as promising drug targets. Keeping this thing in mind, proteome of Pseudomonas aeruginosa PA01 was explored, which resulted in the identification of tripartite protein complexes (MexA, MexB, and OprM) as promising drug target for the screening of natural and synthetic inhibitors. The purpose of present investigation was to explore the drug resistance reversal potential mechanism of catharanthine isolated from the leaves of Catharanthus roseous. Hence, the test compound catharanthine was in silico screened using docking studies against the above receptors, which showed significant binding affinity with these receptors. In order to validate the in silico findings, in vitro evaluation of the test compound was also carried out. In combination, catharanthine reduced the minimum inhibitory concentration MIC of tetracycline (TET) and streptomycin up to 16 and 8 folds, respectively. Further, in time kill assay, catharanthine in combination with TET reduced the cell viability in concentration dependent manner and was also able to reduce the mutation prevention concentration of TET. It was also deduced that drug resistance reversal potential of catharanthine was due to inhibition of the efflux pumps.