Identification of Escherichia coli enterotoxin inhibitors from traditional medicinal herbs by in silico, in vitro, and in vivo analyses.
BACKGROUND
Glycyrrhiza uralensis has been used for the treatment of gastrointestinal disorders, such as diarrhea, in several ancient cultures. Glycyrrhizin is the principal component of liquorice and lots of pharmacological effects have been demonstrated.


OBJECTIVE
Heat-labile enterotoxin (LT), the virulence factor of enterotoxigenic Escherichia coli, induces diarrhea by initially binding to the GM1 on the surfaces of intestinal epithelial cells and consequently leading to the massive loss of fluid and ions from cells. Therefore, we evaluated the inhibitory effects of traditional medicinal herbs (TMH) on the B subunit of LT (LTB) and GM1 interaction.


METHODS
The inhibitory effects of TMH on LTB-GM1 interaction were evaluated by GM1-enzyme-linked immunosorbent assay (ELISA). The likely active phytochemicals of these TMH were then predicted by in silico model (docking) and analyzed by in vitro (GM1-ELISA) and in vivo (patent mouse gut assay) models.


RESULTS
We found that various TMH, which have been ethnomedically used for the treatment of diarrhea, inhibited the LTB-GM1 interaction. Docking data showed that triterpenoids were the most active phytochemicals and the oleanane-type triterpenoids presented better LTB-binding abilities than other types of triterpenoids. Moreover, by in vitro and in vivo models, we demonstrated that glycyrrhizin was the most effective oleanane-type triterpenoid that significantly suppressed both the LTB-binding ability (IC50=3.26+/-0.17 mM) and the LT-induced fluid accumulation in mice.


CONCLUSIONS
We found an LT inhibitor, glycyrrhizin, from TMH by in silico, in vitro, and in vivo analyses.
Chen
Jaw-Chyun
JC
Graduate Institute of Chinese Pharmaceutical Sciences, China Medical University, Taichung, Taiwan.
Ho
Tin-Yun
TY
Chang
Yuan-Shiun
YS
Wu
Shih-Lu
SL
Li
Chia-Cheng
CC
Hsiang
Chien-Yun
CY
D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D003967:Diarrhea / Q000139:chemically induced / Q000517:prevention & control*; D054307:Enterotoxigenic Escherichia coli / Q000187:drug effects* / Q000472:pathogenicity; D004768:Enterotoxins / Q000037:antagonists & inhibitors*; D004927:Escherichia coli Infections / Q000188:drug therapy*; D005260:Female; D005732:Gangliosides / Q000737:chemistry; D029882:Glycyrrhiza uralensis; D019695:Glycyrrhizic Acid / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D066298:In Vitro Techniques; D051379:Mice; D008807:Mice, Inbred BALB C; D009828:Oleanolic Acid / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D008517:Phytotherapy; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D037521:Virulence Factors
D000900:Anti-Bacterial Agents; D004768:Enterotoxins; D005732:Gangliosides; D010936:Plant Extracts; D037521:Virulence Factors; D019695:Glycyrrhizic Acid; D009828:Oleanolic Acid