Antimicrobial and antioxidant potentials of an endophytic cunninghamella sp. isolated from the leaves of Chrysophyllum albidum

Abstract

Background: Several studies have identified endophytic fungi associated with Nigerian plants as potential sources of new drug discovery. Aim: This study was carried out to investigate the antimicrobial and antioxidant properties of secondary metabolites isolated from an endophytic Cunninghamella sp. associated with leaves of Chrysophyllum albidum, a Nigerian indigenous plant. Method: The plant material was collected in Agulu, Anambra State, South-East Nigeria. Endophytic fungal isolation and identification, as well as fermentation and extraction of fungal secondary metabolites, were carried out using standard methods. The antimicrobial and antioxidant activities of the fungal extract were evaluated using the agar well diffusion method and the 1,1-diphenyl-2-picryl-hydraxyl (DPPH) free radical assay, respectively. Result: An endophytic fungus was isolated from the leaves of C. albidum. Following a molecular identification protocol of DNA amplification and sequencing of the fungal ITS region, the fungus was identified as Cunninghamella sp. The fungal extract exhibited antimicrobial activity against the test bacteria and fungus. At concentrations ranging from 2.5 - 20 mg/mL, the extract produced inhibition zone diameters (IZD) ranging from 2 - 11 mm against Pseudomonas aeruginosa. Antibacterial activity was also observed against Staphylococcus aureus at concentrations ranging from 10 - 20 mg/mL, with IZD ranging from 3 - 6 mm. Antifungal activity was observed against Candida albicans at concentrations ranging from 1.25 - 20 mg/mL, with IZD ranging from 2 - 7 mm. The fungal extract demonstrated significant antioxidant activity in the DPPH assay when compared to the standard control, quercetin. The extract showed a percentage inhibition range of 95 - 98% at concentrations ranging from 20 to 100 µg/mL. Conclusion: The findings of this study highlight the potential of endophytic Cunninghamella sp. and other endophytic microorganisms of indigenous Nigerian plants as sources of bioactive compounds with antimicrobial and antioxidant properties for pharmaceutical and industrial applications.