Antibacterial activity of secondary metabolites from Aspergillus awamori F12 isolated from rhizospheric soil of Rhizophora stylosa Griff

Abstract:

Abstract: [Objective] To identify Aspergillus awamori strain F12 isolated from rhizospheric soil of Rhizophora stylosa Griff and to characterize antibacterial compounds from the ethyl acetate extracts of its fermentation broth. [Methods] Strain F12 was identified based on its morphological characters and internal transcribed spacer (ITS) sequence. Its secondary metabolites were purified by chromatography, and elucidated by mass spectroscopy, 1H-NMR, 13C-NMR and physicochemical characters. The antibacterial activities of these compounds were tested against Staphyloccocus aureus and Bacillus subtilis. [Results] Strain F12 was identified as Aspergillus awamori. Three compounds, including 1,4-dimethoxybenzene (1), emodin (2) and 3, 6-dibenzylpiperazine-2, 5-dione (3), were purified and elucidated from the ethyl acetate extracts of fermentation broth, among which compound 1 was first reported for the genus of Aspergillus. Compound 2 suppressed the growth of Staphyloccocus aureus and Bacillus subtilis with MIC values of 16 μg/mL and 32 μg/mL respectively, while the other two compounds have no effects on these bacteria. [Conclusion] Aspergillus awamori strain F12 isolated from rhizospheric soil of Rhizophora stylosa Griff can produce 1, 4-dimethoxybenzene and emodin, among which the latter can suppress the growth of bacteria apparently.