Metabolite profiling, in vitro and in silico assessment of antibacterial and anticancer activities of Alternaria alternata endophytic in Jatropha heynei.

Fungal endophytes produce a range of structurally diverse metabolites with bioactive principles. In this study, an endophytic fungus Alternaria alternata was isolated from Jatropha heynei and cultured in potato dextrose liquid broth. Culture filtrate of A. alternata was extracted in ethyl acetate and metabolites were characterized by QTOF-HRLCMS. Among compounds detected, spectral compounds such as kigelinone, and levofuraltadone were reported with antibacterial property, while 2-hydroxychrasophanol, isoathyriol, glycophymoline, columbianetin and kaempferol 3-O-β-D- galactoside were reported with cytotoxic properties. Partially purified metabolites of A. alternata showed significant antibacterial activity against tested clinical bacterial strains by agar well diffusion method. High zone of inhibition was recorded against Enterococcus faecalis, Pseudomonas syringae and Klebsiella pneumoniae. In vitro anticancer activity of fungal extract by MTT assay displayed high cytotoxic effect on human lung carcinoma cancer cell line (A549) with IC value of 393.52 µg ml, and without any significant cytotoxic effect on human breast cancer cell line (MCF-7). Further, antibacterial and anticancer spectral compounds of A. alternata were subjected to molecular docking analysis with antibacterial target proteins such as tellurite resistance protein (2JXU), indole-3-acetaldehyde dehydrogenase (5IUU) and alkyl hydroperoxide reductase (5Y63), and anticancer target human apoptotic regulator protein (1G5M). The results of the study indicated that kigelinone, levofuraltadone, 2-hydroxychrasophanol and isoathyriol in the fungal extract have significant binding modes, with best binding energy scores with their respective antibacterial and anticancer target proteins. Alternaria alternata resident in J. heynei offers a promising source of broad-spectrum antibacterial and anticancer compounds.