Strategic Optimisation of Growth and Production of Bioactive Compounds in Nigrospora oryzae, an Endophytic Fungus Associated with Dioscorea bulbifera L.

An endophytic fungus Nigrospora oryzae was isolated from Dioscorea bulbifera L., an important ethnomedicinal plant. A huge repertoire of natural products produced by the endophytic fungus exhibits various biological activities. The current study aimed at the optimisation of process parameters for the growth of N. oryzae and production of secondary metabolites. The optimized process parameters were used for the fermentation and production of secondary metabolites. It was followed by the isolation, purification, and characterization of structurally diverse and biologically significant compounds from the fermented extract of endophytic fungus, N. oryzae and assessment of their bioactive potential. Herein, we described the yield of two anthraquinone derivatives, nigrosporin B (1) and acetoxybostrycin (2) based on the spectral data from the pure fractions F1 and F2. Anthraquinones and their derivatives have drawn widespread attention as potential drug candidates. The compounds (1) and (2) exhibited strong inhibition potential against Staphylococcus aureus, Bacillus cereus and Escherichia coli. The compounds (1) and (2) demonstrated significant results for α-glucosidase inhibitory activity. Further, GC-MS analysis of the two fractions, F3 and F4, revealed the presence of specific fatty acids, including nervonic, oleic, linoleic, erucic, palmitic, caprylic, and stearic acids that exhibited α-glucosidase inhibitory activity. The experimental data showed that these endophytic secondary metabolites open up new perspectives for their usage as substantial targets for therapeutic drug discovery and management of diseases.