Yang Liang, Ding Wei, Xu Yuquan, Wu Dousheng, Li Shili, Chen Juanni, Guo Bing
Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University, Chongqing 400715, China.
Biotechnology Research Institute, The Chinese Academy of Agricultural Sciences, Beijing 100081, China.
Molecules. 2016 Apr 8;21(4):468. doi: 10.3390/molecules21040468.
Coumarins are important plant-derived natural products with wide-ranging bioactivities and extensive applications. In this study, we evaluated for the first time the antibacterial activity and mechanisms of action of coumarins against the phytopathogen Ralstonia solanacearum, and investigated the effect of functional group substitution. We first tested the antibacterial activity of 18 plant-derived coumarins with different substitution patterns, and found that daphnetin, esculetin, xanthotol, and umbelliferone significantly inhibited the growth of R. solanacearum. Daphnetin showed the strongest antibacterial activity, followed by esculetin and umbelliferone, with MICs of 64, 192, and 256 mg/L, respectively, better than the archetypal coumarin with 384 mg/L. We further demonstrated that the hydroxylation of coumarins at the C-6, C-7 or C-8 position significantly enhanced the antibacterial activity against R. solanacearum. Transmission electron microscope (TEM) and fluorescence microscopy images showed that hydroxycoumarins may interact with the pathogen by mechanically destroying the cell membrane and inhibiting biofilm formation. The antibiofilm effect of hydroxycoumarins may relate to the repression of flagellar genes fliA and flhC. These physiological changes in R. solanacearum caused by hydroxycoumarins can provide information for integral pathogen control. The present findings demonstrated that hydroxycoumarins have superior antibacterial activity against the phytopathogen R. solanacearum, and thus have the potential to be applied for controlling plant bacterial wilt.
香豆素是一类重要的植物源天然产物，具有广泛的生物活性和广泛的应用。在本研究中，我们首次评估了香豆素对植物病原菌青枯雷尔氏菌的抗菌活性及其作用机制，并研究了官能团取代的影响。我们首先测试了18种具有不同取代模式的植物源香豆素的抗菌活性，发现瑞香素、七叶亭、花椒毒素和伞形花内酯显著抑制青枯雷尔氏菌的生长。瑞香素表现出最强的抗菌活性，其次是七叶亭和伞形花内酯，其最低抑菌浓度分别为64、192和256mg/L，优于原型香豆素的384mg/L。我们进一步证明，香豆素在C-6、C-7或C-8位的羟基化显著增强了对青枯雷尔氏菌的抗菌活性。透射电子显微镜（TEM）和荧光显微镜图像显示，羟基香豆素可能通过机械破坏细胞膜和抑制生物膜形成与病原体相互作用。羟基香豆素的抗生物膜作用可能与鞭毛基因fliA和flhC的抑制有关。羟基香豆素引起的青枯雷尔氏菌的这些生理变化可为整体病原菌控制提供信息。目前的研究结果表明，羟基香豆素对植物病原菌青枯雷尔氏菌具有优异的抗菌活性，因此具有应用于防治植物青枯病的潜力。
