赣南两种半枫荷属植物抗柑橘溃疡病菌活性三萜的发现及其作用机理研究

Citrus canker, caused by the pathogen Xanthomonas citri subsp. citri, leads to huge economic loss by deteriorating quality and reducing quantity of citrus fruits. The wide-used pesticides controlling this disease currently, had a lots of severe disadvantages such as difficult degradation, environmental pollution, limited effect, and inducing the production of antibiotic-resistant bacteria, making the discovery of novel environmentally friendly pesticides highly urgent. In the process of searching for high-effect and environmentally benign pesticides from natural resources, we fortunately identified two wild plants, Semiliquidambar cathayensis Chang and Semiliquidambar chingii (Metc.) Chang, belonging to the genus Semiliquidambar, all of whose crude extracts exhibited not only excellent anti-bacterial effect against the Xanthomonas citri subsp. citri, but also displayed rich chemical fingerprint in HPLC profile, intriguing our great interest for further investigation. Previously, over ten bioactive triterpenoids were isolated from the species Semiliquidambar chingii (Metc.) Chang. Based on the preliminary SAR research on compounds isolated, one oleanolic acid derivative with excellent anti-bacterial effect, better than the positive control CuSO4, was designed and synthesized. In this proposal, the applicants plan to systemically explore the bioactive secondary metabolites of these two target plants, using the bioassay platforms of inhibiting bacterial growth and inhibiting the bacterial biofilm formation. Afterwards, the applicants will carry out the comprehensive SAR research toward the bioactive molecules using modern organic synthetic method, figuring out the groups or moieties responsible for biological effect, followed by the exploration of the antibacterial mechanism underlying the bioactivity. The successful accomplishment of our proposal will result in the discovery of potential lead compounds against the pathogen Xanthomonas citri subsp. citri, highly contributing to the production of environmentally friendly novel pesticides controlling the disease citrus canker.

由病原菌柑橘黄单胞柑橘亚种 (Xanthomonas citri subsp. citri) 引起的柑橘溃疡病给柑橘产业造成严重经济损失。目前常用防治药剂存在难降解、破坏生态环境、防治效果有限及产生耐药菌等严重问题。前期研究发现，赣南地区两种半枫荷属植物（半枫荷及细柄半枫荷）粗提物均显示很好的抗柑橘溃疡病菌活性。已从细柄半枫荷中分离获得15个三萜类活性化合物，通过构效关系研究，成功合成一个齐墩果酸衍生物，其抗柑橘溃疡病菌活性好于阳性对照硫酸铜。申请人拟在资金的资助下，综合运用抑制柑橘溃疡病菌生长及抑制该病菌生物膜形成这两个活性筛选平台，双管齐下，首次从这两种目标植物中系统发掘抗柑橘溃疡病菌活性分子，尤其是三萜化合物，研究构效关系，总结显效基团，探讨抗菌机理，以获得结构明确、活性显著的新型柑橘溃疡病农药先导化合物，为研制开发具有自主知识产权的绿色高效柑橘溃疡病农药奠定基础。

由病原菌柑橘黄单胞柑橘亚种 (Xanthomonas citri subsp. citri) 引起的柑橘溃疡病给柑橘产业造成严重经济损失。目前常用防治药剂存在难降解、破坏生态环境、防治效果有限及产生耐药菌等严重问题。课题按照研究计划，对前期发现的两种半枫荷属植物（半枫荷及细柄半枫荷）中抗柑橘溃疡病菌活性物质开展了活性追踪分离以及抗菌作用机理研究。在此基础上，利用已经建立起来的抗菌活性平台，开展了赣南脐橙果皮及其内生菌的抗柑橘溃疡病菌活性研究。从两种半枫荷属植物、赣南脐橙果皮及其一株内生菌中分离鉴定了一系列具有显著抗柑橘溃疡病菌的活性分子。基于生长曲线、可溶性糖消耗量、胞外蛋白含量、生物膜形成抑制率、体内ROS水平以及扫描电镜分析等技术，研究了活性成分的抗柑橘溃疡病菌作用机理。结合构效关系及盆栽实验研究，发现多个具有应用开发潜能的柑橘溃疡病农药先导分子。在基金的资助下，申请人也开展了半枫荷提取物的抗炎活性研究，为半枫荷在民间治疗炎症相关疾病中的应用提供理论依据。同时，结合地方经济发展需求，申请人在完成项目书研究内容的同时，利用基金资助建立的实验平台，开展了赣南地方特色柑橘资源的综合开发利用研究。项目执行期间，相关研究成果以第一或者通讯作者发表SCI收录研究论文8篇，申请发明专利2项，培养研究生4名。项目研究结果将为半枫荷属植物资源的开发利用以及绿色高效柑橘溃疡病农药的研制提供科学依据和理论基础。

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