ABSTRACT
The search and discovery of new natural products with antifeedant and larvicidal potentials to mitigate harmful insects are scientific pressing issues in the modern agriculture. In this paper, the antifeedant and larvicidal potentials of 69 fungal isolates were screened against the Egyptian cotton leafworm Spodoptera littoralis. A total of 17 isolates showed the insecticidal potentials with three promising isolates. These strains were Aspergillus sydowii, Lasiodiplodia theobromae, and Aspergillus flavus isolated from Ricinus communis (bark), Terminalia arjuna (Bark), and Psidium guajava (twigs), respectively. The effect of gamma irradiation on the antifeedant and larvicidal activities of the three strains was investigated. Exposure of the fungal spores to 1000 Gy of gamma rays significantly intensified both the antifeedant and larvicidal potentials. To identify compounds responsible for these activities, extracts of the three strains were fractionated by thin layer chromatography. The nature of the separated compounds namely, Penitrem A, 1, 3, 5, 8- tetramethyl- 4, 6-diethyl- 7- [2- (methoxycarbonyl)ethyl] porphyrin (from A. sydowii), Penitrem A, 2, 7, 12, 17-Tetramethyl-3, 5:8, 10:13, 15:18, 20-tetrakis (2,2-dimethylpropano) porphyrin (from A. flavus), N,N-Diethyl-3-nitrobenzamide, and Diisooctyl-phthalate (from L. theobromae) were studied by GC-MS analysis. These findings recommend endophytic fungi as promising sources of novel natural compounds to mitigate harmful insects.
ABSTRACT
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.
