Anti-oxidant and anti-microbial potentials of some metabolites from an endophytic fungi isolated from Lorantus micranthus from south-eastern Nigeria

Abstract

Endophytes are currently considered as a well spring of novel secondary metabolites; offering the potential for medical, pharmaceutical, agricultural and industrial exploitation. This study aims at assessing the anti-oxidant and antimicrobial activities of the ethyl acetate extract of the metabolites produced by two endophytic fungi isolated from Loranthus micranthus, fermented on rice media. The healthy part of thee leaf was washed under tap water and cut into small fragments of 2 mm length. Stabilization and growth of endophytic fungi, solid state fermentation and isolation of the pure fungi was done following an established standard methods [1, 2]. Phytochemical analysis of the extracts reveals the presence of alkaloids, flavonoids, tannins, reducing sugar, steroids and proteins. The antimicrobial activity of the ethyl acetate extract of the secondary metabolites isolated from endophytic Aspergillus fumigatus identified by cultural and microscopic features was evaluated using the agar well diffusion method. The following test organisms were used; Staphylococcus aureus, Klebsiella pneumoniae, Salmonella typhi, Bacillus subtilis, Candida albicans and A. fumigatus. At the concentrations analyzed (5 – 0.625 mg/mL), the extract recorded only antibacterial and no antifungal activity against the test isolates. Antibacterial activity was observed against all test bacteria at 5 and 2.5 mg/mL; while at 1.25 mg/mL inhibition zone diameters (IZDs) of 2, 2, 0 and 4 mm were recorded against S. aureus, S. typhi, K. pneumoniae and B. subtilis, respectively. At 0.625 mg/mL, antibacterial activity was recorded only against B. subtilis with an IZD of 3 mm. No IZD was recorded against C. albicans and A. fumigatus at the various concentrations analyzed. The extracts exhibited poor DPPH radical scavenging assay activity. The measured DPPH activity at 100 µg was 15.8% – 12% of inhibition as compared to 47 and 74% of inhibition of Rutin and BHT positive controls.