Screening of secondary metabolites produced by a mangroove-derived Nigrospora species an endophytic fungus isolated from Rhizophora racemosa for antioxidant and antimicrobial properties

Abstract

Marine fungi have shown large chemo-diversity of unharnessed important secondary metabolites required for drug development. In this study, endophytic fungi Nigrospora species (5S3) was isolated from the fresh stem of Rhizophora racemosa from a mangrove forest in Lagos Nigeria and axenic colonies were fermented on sterile rice medium for 21 days. The antimicrobial and antioxidant activities of the extract were evaluated. Chemical analyses such as High Performance Liquid Chromatography Diode Array Detector (HPLC-DAD) and Nuclear magnetic Resonance Imaging (NMR) analyses of selected Vacuum Liquid Chromatography (VLC) fractions revealed the presence of ten known compounds with established biological activities. Tested fractions of the extract exhibited antimicrobial activities against at least one Gram positive and Gram negative bacteria with MIC values that ranged between 0.13 to 1 mg/mL. FE2 and FE3 fractions of the extract demonstrated poor antioxidant activity of less than 10%. Septicine, Aureonitol, Papuamine, Di-iso-octylphtalat, 1-(2,4 Dihydroxy-3,5-Dimethylphenyl)-Ethanone, Cladosporin, Tetrabenzofuran, Dihydrophthalate, 9-Octadecaenoic acid and Eicosane were the compounds detected in the extracts. Our findings reveal that Nigrospora spp an endophytic fungi possesses unique chemo diversity of bioactive secondary metabolites that could be utilized for development of new drugs.