ASSESSMENT OF SECONDARY METABOLITES AND ANTIOXIDANT ACTIVITY OF FUNGAL ENDOPHYTES ISOLATED FROM Ziziphus jujuba MILL

The present study aimed to isolate, characterize and assess the total phenol, flavonoid content along with the antioxidant activity of fungal endophytes isolated from Ziziphus jujuba Mill. from different parts of Burdwan town in Purba Bardhaman district of West Bengal, India. Isolation of fungal endophytes was carried out following the standard protocol using potato dextrose agar (PDA) media. Identification, determination of colonization frequency of the fungal endophytes, fermentation and extraction was done as stated in the standard protocol. Qualitative assay of the bioactive compound has been investigated following the standard procedures. Quantitative estimation of total phenol and flavonoid content was performed following the standard spectrophotometric methods. The antioxidant activity of the cell-free extract was determined by phosphomolybdenum assay and 2, 2- diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method. IC50 values of the fungal endophytes were determined from DPPH free radical scavenging.

Four dominant endophytic fungi from Ziziphus jujuba with maximum colonization frequency in ZSS2 (Cladosporium sp. 1) and ZSS4 (Aspergillus sp. 1) have been isolated and identified. Qualitative detection of secondary metabolites revealed that ZSS1 (Curvularia sp. 1) and ZSS4 (Aspergillus sp. 1) were found to be positive for the synthesis of various functional metabolites tested in this study. The quantitative study suggests that the production of the highest amount of phenol and flavonoid was observed in ZSS1 followed by ZSS4. The highest antioxidant activity was exhibited by ZSS1 in both total antioxidant capacity (TAC) by phosphomolybdenum assay and free radical scavenging activity (inhibition%). A significant positive correlation was found between the total phenol and flavonoid content and corresponding antioxidant activity of the fungal extract. The present investigation thus gives an insight that the secondary metabolites produced by the endophytic fungi isolated from Ziziphus jujuba Mill. would be a potential source of novel natural antioxidant compounds.