Bioactive compounds and antibacterial activity of endophytic fungi isolated from Black Mangrove (<i>Avicennia africana</i>) leaves

Abstract

The antibacterial potential of fungal endophytes from black mangrove against pathogenic marine bacteria was evaluated and the bioactive compounds identified and quantified. Black mangrove (Avicennia africana) healthy leaves were obtained from a Mangrove Forest in Eagle Island, Port Harcourt, Nigeria. The fungal endophytes were cultured on acidified Potato dextrose agar plates for 5 days at 28^oC. The isolated fungal endophytes were identified based on microscopic and colonial morphologies. Different concentrations (0, 20, 40, 60, 80 and 100 mg/ml) of ethyl acetate extract of the fungal isolates were screened against pathogenic marine bacteria (Salmonella spp., Staphylococcus aureus and Shigella spp.) via agar well diffusion assay. The most active isolate was identified using molecular method. Gas chromatography – Mass spectrometry was employed in the identification and quantification of its bioactive secondary products. Fungi of the genera Aspergillus, Penicillium, Fusarium, Collectotrichum, Phomopsis, Epicoccum and Rhizopus were isolated. Two bioactive compounds were identified in ethyl acetate extract of Fusarium sp. which was molecularly identified as Fusarium phyllophilum KU350622.1. Dibutyl phthalate (C₁₆H₂₂O₄ ) is the major compound at 55.926% peak area. The results showed that fungal endophytes from black mangrove exhibited antibacterial action against pathogenic marine bacteria. The bioactive secondary products identified have vast potentials for use in agriculture and industries.

Keywords: Avicennia africana, fungal endophytes, antibacterial activity, bioactive compounds