Antibacterial Activity of Endophytic Fungi Isolated from Rapanea melanophloeos (Myrsinaceae)

Abstract

Background: Endophytic fungi associated with medicinal plants may produce compounds with antibacterial effects, but the culturable fungal endophytes of Rapanea melanophloeos remain insufficiently characterised. Aims: This study aimed to isolate fungal endophytes from the leaves, stem bark and roots of Rapanea melanophloeos and evaluate their antibacterial potential. Study design: Fresh material was collected in March 2024 from the Botanical Garden at Egerton University and used to isolate endophytic fungi. The resulting cultures were maintained on potato dextrose agar. Place and Duration of Study: The work was conducted in the Department of Chemistry, Biotechnology Laboratory, Egerton University, between March and December 2024. Methodology: Root, stem and leaf segments underwent surface disinfection using 70% ethanol, followed by 2% sodium hypochlorite and sterile distilled water. Fungal isolates were cultured on potato dextrose agar, and their antibacterial activity was assessed by a dual-culture assay. Inhibition-zone diameters were recorded in millimetres. The bacterial panel comprised Staphylococcus aureus (ATCC259923), Escherichia coli (ATCC25922), Streptococcus agalactiae, Klebsiella pneumoniae (ATCC70063) and Pseudomonas aeruginosa (ATCC27853). Results: A total of 25 fungal endophytes were recovered, with most isolates originating from stem bark (75%), followed by roots (17%) and leaves (8%). Across the bacterial tests, inhibition-zone diameters ranged from 11.5 to 44.6 mm. All recovered isolates inhibited E. coli, with reported zones of 11.5–32.5 mm. Conclusion: Endophytic fungi associated with R. melanophloeos showed antibacterial potential and may constitute sources of biologically active compounds of pharmaceutical interest.