Bioactive potential of culturable fungal endophytes isolated from leaf of Catharanthus roseus (L.) G. Don.

Introduction Endophyte is considered as 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 pathogen. Hence, CATDLF7 crude extract was subjected to the 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,β-dehydrocurvularin. This compound also showed synergistic interaction with norfloxacin, and reduced its MIC up to 32-folds with fractional inhibitory concentration index (FICI) of 0.09. Results To understand the possible antibacterial mechanism of action, α,β-dehydrocurvularin alone (100 μg/ml) exhibited efflux pump inhibitory potential by 0.84 fold decreasing in ethidium bromide (EtBr) fluorescence. In addition, α,β-dehydrocurvularin inhibited inflammatory cytokines TNF-α and IL-6 production which is further validated by molecular docking score -4.921 and -5.641 respectively for understanding orientation and binding affinity. Conclusion Overall the results highlighted to identifying bioactive compound α,β-dehydrocurvularin which could be used as an antimicrobial and anti-inflammatory agents.