黄蜻幼虫肠道菌QTYC01除草活性代谢产物的分离和鉴定

Phytotoxic metabolite from QTYC01, a fungus residing in the gut of Pantala flavescens larvae

摘要:

[目的]从黄蜻幼虫肠道中分离出具有除草活性的真菌，并在其代谢产物中寻找具有除草活性的先导化合物。[方法]采用涂布平板法对黄蜻幼虫肠道共生真菌进行分离，通过形态学观察和5.8SrRNA序列分析初步确定目标菌株QTYC01的分类地位。利用离体的方法测定菌株发酵液及其乙酸乙酯提取物的除草活性以及粗提物对常见农作物的安全性；利用盆栽方法测定发酵液对稗草幼苗的活性。运用重结晶的方法对发酵产物进行分离、纯化，利用质谱和核磁共振谱分析鉴定出化合物的结构。[结果]菌株QTYC01被鉴定为Curvularia crepinii。离体活性测试发现QTYC01发酵液可显著抑制稗草和反枝苋幼根的生长，其抑制率分别可达95.0%和90.1%，并可使经喷施发酵液的稗草幼苗的受害率达到71.1%。发酵液的乙酸乙酯提取物对稗草和反枝苋幼根具有很好的抑制效果，在100 μg/mL的浓度条件下，粗提物对稗草和反枝苋的抑制活性分别为56.8%和71.2%，且在该浓度条件下对一些常见农作物具有很好的安全性，其抑制率均低于32.6%。进一步从其乙酸乙酯提取物中分离得到化合物（5Z）-7-oxozeaenol，活性测试表明化合物具有较好的抑制反枝苋活性，其IC₅₀为4.8 μg/mL。[结论]菌株QTYC01具有开发为新型微生物除草剂的潜力。

Abstract:

[Objective] To isolate the fungus with phytotoxic activity from the gut of Pantala flavescens larvae and find the phytotoxic lead compound from the fungal metabolites.[Methods] QTYC01 was isolated from the gut of P. flavescens larvae by means of spread plate and identified by 5.8S rRNA sequence analysis and morphologic observation. Phytotoxic activities of the fermentation broth and ethyl acetate extracts against the radical growth of weeds as well as the safety of crude extract to the selected crops were tested by Petri dish bioassay. The herbicidal activity of QTYC01 against Echinochloa crusgalli seedlings was carried out by potted bioassay. Fermentation product was purified by recrystallization and identified by extensive spectroscopic analysis.[Results] QTYC01 was identified as Curvularia crepinii. The fermentation broth of QTYC01 significantly inhibited the radical growth of E. crusgalli and Amaranthus retroflexus with the inhibition rate of 95.0% and 90.1%, respectively. The fermented liquid showed significant inhibitory activity to the seedling of E. crusgalli with the victimization rate of 71.1%. Under the concentration of 100 μg/mL, ethyl acetate extracts exhibited significant phytotoxic activities against the radical growth of E. crusgalli and A. retroflexus with inhibitory rates of 56.8% and 71.2%, respectively, and showed good security to the selected common crops with the inhibition rate of lower than 33%. Therewith, a bioactive compound was isolated from the ethyl acetate extract and determined as (5Z)-7-oxozeaenol. The compound showed good phytotoxic activity against A. retroflexus with the IC₅₀ value of 4.8 μg/mL.[Conclusion] Strain QTYC01 could be potentially developed as a new microbial herbicide.