Bioprospecting endophytic fungi for bioactive metabolites and use of irradiation to improve their bioactivities

The search for new bioactive compounds with innovative modes of action and chemistry are desperately needed to tackle the increased emergence of drug-resistant microbes. With this view, this paper was conducted for the isolation, identification, and biological evaluation of fungal endophytes of eleven different plant species. A total of 69 endophytic strains were isolated and tested for the presence of bioactive metabolites with antifungal, antibacterial, anticancer, and antioxidant properties in their extracts. Upon screening, two promising strains were found to have all the before-mentioned activities. These strains were Aspergillus sydowii isolated from the bark of Ricinus communis and Aspergillus flavus isolated from the twigs of Psidium guajava. Major compounds present in extracts of the two strains were identified by GC-Mass analyses. Several well-known bioactive compounds as well as unreported ones were identified in the fungal extracts of the two strains. Furthermore, gamma irradiation (at 1000 Gy) of the fungal cultures resulted in improved bioactivities of extracts from the two strains. These findings recommend the two fungal strains as sources of antimicrobial, anticancer, and antioxidant compounds which may aid in the development of novel drugs. The presented research also explains the high-value of fungal endophytes as untapped sources of bioactive metabolites.