Isolation and identification of bioactive secondary metabolites produced by strain QTYC38, a fungus isolated from the gut of Pantala flavescens larvae

Abstract:

[Objective] To identify strain QTYC38, a fungus isolated from the gut of Pantala flavescens larvae, and study its phytotoxic and antimicrobial metabolites.[Methods] QTYC38 was identified by morphological observation and molecular biological analysis. Growth rate method and agar disc diffusion assays were used to test the antimicrobial activities. Petri-dish bioassay was used to test the phytotoxic activity. Bioactive components were isolated via chromatographic methods, and the structures were determined by mass spectrum and nuclear magnetic resonance analyses.[Results] QTYC38 was identified as Neosartorya aureola. Ethyl acetate extract of QTYC38 inhibited radical growth of Echinochloa crusgalli and Amaranthus retroflexus with the inhibition rates above 65% with the concentration of 100 μg/mL, The extract also inhibited Staphyloccocus aureus with the mean halo diameter of 22.7 mm with the concentration of 30 μg/filter. Four compounds were purified from the solid fermentation product:helvolic acid, aromatic lactones, questin and erogosterol. Helvolic acid inhibited the growth of Bacillus subtilis and S. aureus with the MIC values of 3.1 and 1.5 μg/mL, respectively. Questin and erogosterol inhibited Dothiorella gregaria and Fusarium graminearum at the concentration of 100 μg/mL, with the inhibition rates of 52.4% and 71.3%, respectively.[Conclusion] Strain QTYC38 could be potentially developed as a microbial herbicide and new antimicrobial agent.