Antimicrobial and antioxidant potentials of crude extracts of culturally dissimilar endophytic fungi

Endophytes from an unexplored plant such as Spatterdock (SD) Nuphar lutea variegata could be a dependable producer of novel secondary metabolites active against drug resistance organisms. This study explored the diversity of fungal endophytes from mid-rib (MR) and leaf blade (LB) of Nuphar lutea variegata as well as the antimicrobial and antioxidant potentials of their secondary metabolites. Morphological features observed showed four species were isolated. A broad-spectrum antimicrobial activity observed to be concentration-dependent was observed for all the fungal crude extracts 1 mg/mL. Crude extract of SD-LB3 showed the best antibacterial activities against S. aureus and P. aeruginosa with a minimum inhibitory concentration of 0.5 and 0.25 µg/mL respectively. The antioxidant capacities of the fungal crude extracts showed a better neutralizing effect of free radicals compared to the standard Quercitin. Effective inhibition of free radicals was observed for all the fungal extracts from 20 to 100 mg/mL (96.7 – 99.3 %). The highest antioxidant activity was shown by the extracts of fungi isolated from the leaf blade with an average of 98 to 99.2 % at the tested concentrations of 20 to 100 mg/mL. Our study provides evidence of diverse endophytic fungi associated with Nuphar lutea variegata, and the antibacterial and antioxidant activities observed confirm their capacities as producers of bioactive secondary metabolites.

This study is the first to isolate endophytic fungi form Nuphar lutea variegata and screen the antimicrobial and antioxidant activities of their secondary metabolites.