每年有數百萬人死於下痢相關疾病，腸產毒素性大腸桿菌(enterotoxigenic E. coli)則是其中最常被分離出的菌株。然而其導致下痢最主要的毒力因子為其所分泌的忌熱性腸毒素(heat-labile enterotoxin; LT)，其作用機轉是經由B 次單位(B subunit of LT; LTB) 先與腸上皮細胞表面的神經苷節脂(ganglioside GM1)結合而發揮毒力並誘發下痢相關的症狀。因此我們以一分子生物學分析平台(Competitive GM1-ELISA)搜尋常用中草藥，尋找能抑制LTB 和GM1的結合作用的中草藥。其中發現五倍子、木瓜、甘草等中草藥萃取物，可有效抑制LTB 結合到GM1 能力。進ㄧ步搜尋並分析這些中草藥中可能的抗下痢活性成分，結果顯示五倍子中的沒食子酸、木瓜所含之三萜類化合物(齊墩果酸、熊果酸和樺木酸)以及甘草的甘草甜素，均對GM1 與LTB 的結合均有不同程度的抑制，且動物實驗證實可抑制腸毒素所誘發的小鼠腸液堆積效應。進ㄧ步以生物資訊工具-分子模擬平台(docking)，分析木瓜及甘草中的三萜類化合物與LTB 之間的交互作用。總而言之，我們成功的以分子生物學及生物資訊學工具，找到中草藥中具抗下痢作用的活性成分。
Enterotoxigenic Escherichia coli (ETEC) is the most frequently isolated enteropathogen, accounting for millions of deaths annually. ETEC-induced diarrhea is initiated by the binding of B subunit of heat-labile enterotoxin (LTB) to the ganglioside GM1 on the surface of intestinal epithelial cell. Therefore, we evaluated the inhibitory effects of traditional Chinese medicine (TCM) on the LTB and GM1 interaction. We found various TCM inhibited the interaction, such as Chinensis Galla, Chaenomelis Fructus and Glycyrrhizae Radix extracts. Then we searched and identified the active components of Chinensis Galla (gallic acid) and Chaenomelis Fructus (oleanolic acid, ursolic acid, betulinic acid). Additionally, we set up a phytochemical database from the TCM to evaluate the anti-toxin-binding ability by docking analysis. Docking results indicated that glycyrrhizin blocked the binding of LTB to GM1, and suppression of LT-induced diarrhea in mice. In conclusion, we have identified inhibitors of LT from TCM by molecular biology and bioinformatics tools.
