Cytotoxicity and antimicrobial activities of secondary metabolites produced by endophytic fungi isolated from Gongronema latifolia and Loranthus micrantus

Abstract

This study was carried out to evaluate the cytotoxicity and antimicrobial properties of secondary metabolites produced by endophytic fungi isolated from Gongronema latifolia and Loranthus micranthus. Isolation of endophytic fungi from plant leaves was carried out using a previously described method. Solid state fermentation was carried out in rice medium for 30 days at 25 – 27 °C and the secondary metabolites were extracted using ethyl acetate. Cytotoxic effects of the extracts were tested on mouse lymphoma cell line (L5178Y) using MTT assay. The antimicrobial properties of the extracts were evaluated using agar well diffusion assay method. HPLC-DAD analysis was carried out to identify the compounds that may be responsible for the recorded activities. Six endophytic molds were isolated from G. latifolia and four from L. micranthus. The results of the cytotoxicity test revealed that the extracts of three fungi from G. latifolia, ACA-L1 – 2.2, ACA-L-1, and ACD-S2 – 1.1 showed significant inhibition of the growth of mouse lymphoma cell line with percentage inhibitions of 57.9, 96.8 and 98.7 respectively. Extracts from two fungi from L. micranthus, ACC-S2 – 1.1 and ACD-S2 – 1.1 showed moderate inhibition of 32.9 and 45.9% respectively, others showed poor activity. At 1 mg/mL, some extracts showed antibacterial activity against all test bacteria. At same concentration, none of the extracts recorded antifungal activity. Extracts from ACC-S2 – 1.1 and ACC-S2 – 2.1 specifically showed good antimicrobial activity against the test bacteria with inhibition zone diameter in the range of 2 – 10 mm. HPLC-DAD analysis of the active extracts revealed the presence of xanthones, depsidones, cinnamic acid, protochatechic acid and indole acetic derivatives. The present study may serve as the baseline for the isolation and characterization of the active molecules which may be used as anticancer or antimicrobial compounds; or as lead compounds for further development into novel therapeutic molecules.