Bioactivity Screening and Identification of Secondary Metabolites from Fungal Endophytes of Carica papaya L. Leaves

Objectives: This work describes the chemical and in-vitro bioactivity studies on endophytic fungi derived from the leaves of Carica papaya L. Methods: Column Chromatography was employed for isolation of fungal metabolites. Nuclear Magnetic Resonance (NMR) spectral data was utilized to elucidate the structure of the isolated compounds and physicochemical properties of them were also examined. As a part of in-vitro bioactivity screening disc diffusion method, 1, 1-diphenyl-2- picryl-hydrazyl (DPPH) scavenging assay and brine shrimp lethality bioassay were conducted to evaluate antimicrobial, antioxidant and cytotoxic activities, respectively. Results: A total of four fungal isolates were identified as endophytic fungi and purified from the young leaves of Carica papaya. These fungi, encoded as CPLE-1, CPLE-2, CPLE-3 and CPLE-4, were identified up to the genus level on the basis of their macroscopic and microscopic characteristics as Colletotrichum sp., Carvularia sp., and next two as Alternaria sp., respectively. Chemical profiling and preliminary bioactivity screening of the fungal endophytes signified strain CPLE-3 with highest potentiality to produce bioactive compounds which directs its large scale cultivation. Ergosterol and Alternariol monomethyl ether were isolated from the ethyl acetate extract of the fungus, CPLE-3. Conclusion: Bioactivity and chemical screening of the endophytic fungal extracts of Carica papaya leaf along with the isolation of fungal secondary metabolites suggested these endophytic fungi to be possible source of bioactive leads for developing new and improved medicines.