Antimicrobial activity of metabolites of an endophytic fungus isolated from the leaves of citrus jambhiri (Rutaceae)

Abstract

Some few studies on the endophytic fungal populations of Nigerian medicinal plants have confirmed the enormous potentials which abound in these organisms as sources of novel bioactive molecules. These studies highlight the need to further explore Nigeria’s plant biodiversity for endophytes producing biologically important molecules. In our study, an endophytic fungus was isolated from the leaves of Citrus jambhiri growing in South-East Nigeria. The fungus was subjected to solid state fermentation on rice medium and the metabolites were extracted using ethyl acetate. The fungal extract was screened for antimicrobial activity and some of the bioactive compounds of the extract were detected using high-performance liquid chromatography (HPLC) analysis. The antimicrobial assay was carried out using the agar diffusion method against several bacterial and fungal strains. The fungal extract, at a concentration of 1 mg/mL, showed antibacterial activity only against Staphylococcus aureus with an inhibition zone diameter (IZD) of 3 mm. No activity against the test fungi was recorded. The HPLC analysis of the extract revealed the presence of three bioactive compounds: protocathechuic acid, indole-3-acetic acid, and acropyrone. Results of this study suggest that endophytic fungi associated with C. jambhiri could be a promising source of novel compounds with pharmacological importance.