Screening of active endophytic fungi derived from Aegiceras corniculatum and their antibacterial chemical constituents

Abstract

In order to explore the antibacterial activity of endophytic fungi derived from Aegiceras corniculatum, antibacterial activity of ferment extract of endophytic fungi was used as evaluation index to screen active strains, the chemical constituents were separated on the basis of bioactivity-guiding method combined with various chromatographic techniques and identified by spectral technique together with comparison with literature data, and the antibacterial activity of pure compounds was determined by microplate method. The results were as follows: (1) Sixteen taxa of endophytic fungi isolated from A. corniculatum were distributed in 2 classes, 7 orders, 10 families and 10 genera. Fusarium was dominant genus. The ferment extract of endophytic fungi GXIMD02029 and GXIMD02039 displayed different levels of inhibitory effects on Bacillus subtilis, Staphylococcus epidermidis, methicillin-resistant S. aureus, Micrococcus luteus, Actinomyces viscosity, and Staphylococcus aureus when that of GXIMD02038 against methicillin-resistant S. aureus, Micrococcus luteus, and Staphylococcus aureus. (2) Seven pure compounds were isolated from endophytic fungi Phomopsis sp. GXIMD02029 and identified as (15R)-acetoxydothiorelone A (1), cytosporone B (2), pestalotiopsone H (3), pestalotiopsone B (4), p-hydroxybenzaldehyde (5), p-hydroxybenzoic acid (6), N-(2-phenylethyl)acetamide (7). (3) Compounds 1 and 2 showed different levels of antibacterial effects. Compound 1 exhibited inhibitory effect on Bacillus subtilis, Staphylococcus epidermidis and methicillin-resistant S. aureus with MIC value of 15.625 g·mL-1, Micrococcus luteus and Actinomyces viscosity with MIC value of 7.812 5 g·mL-1, and Staphylococcus aureus with MIC value of 31.25 g·mL-1. Compound 2 displayed inhibitory effect on Micrococcus luteus with MIC value of 62.5 g·mL-1, Bacillus subtilis, Staphylococcus epidermidis, methicillin-resistant S. aureus and Actinomyces viscosity with MIC values of 125 g·mL-1, and Staphylococcus aureus with MIC value of 250 g·mL-1. Three active strains were reported in the project. It is reported that Compound 1 shows the antibacterial activity for the first time. The result provides the basis for the antibacterial values of endophytic fungi of Aegiceras corniculatum.

Keywords

• aegiceras corniculatum
• endophytic fungi
• antibacterial activity
• chemical constituents
• phomopsis