Abstract This study was undertaken to investigate the biological properties of secondary metabolites of two endophytic fungi (code names: GA and GC) isolated from Psidium guajava leaves. Isolation of the endophytic fungi, fermentation and extraction of fungal secondary metabolites was carried out using standard procedures. The fungal extracts were screened for antimicrobial, antioxidant and cytotoxic activities using the agar well diffusion, DPPH and MTT assay methods respectively. Also, the extracts were subjected to high performance liquid chromatography (HPLC) analysis for the identification of the constituents. Result of the antimicrobial assay revealed that at 1 mg/mL, the crude extract of GA displayed broad spectrum antibacterial activity against all the test bacteria – E. coli, S. aureus, B. subtilis and S. typhi with inhibition zone diameter (IZD) of 5, 6, 5 and 4 mm respectively. Extract of GC showed antibacterial activity only against S. aureus, with IZD of 7 mm. In the DPPH antioxidant assay, GA and GC extracts at 100 µg/mL displayed average antioxidant activity with inhibitions of 56.7 and 55.2% respectively, which is comparable to the 63.7% inhibition recorded for the positive control ascorbic acid. At 10 µg/mL, GA and GC extracts showed poor cytotoxic activities against mouse lymphoma cells L5178Y, with inhibitions of 38.5 and 12.4% respectively.HPLC analysis of GA extract revealed the presence of citreoisocoumarinol, while acropyrone and citreoisocoumarin were detected in the extract of GC. The results of this study indicate that endophytic fungi isolated from leaves of P. guajava produced secondary metabolites that can play vital role in the development of drugs for effective treatment of diseases.
Keywords Psidium guajava, endophytic fungi, secondary metabolites, antioxidant, antimicrobial, cytotoxicity, HPLC analysis.