Identification of the antidiarrhoeal components in official rhubarb using liquid chromatography–tandem mass spectrometry

Though the purgative components in official rhubarb are well documented as anthraquinone glycosides and sennosides, the antidiarrhoeal effect and its chemical basis have not been reported before. In this study, liquid chromatography coupled with electrospray ionisation tandem mass spectrometry was used to investigate the main chemicals in the antidiarrhoeal fraction previously isolated from Rheum palmatum L. In total 10 compounds were identified in the fraction as follows: gallic acid, galloyl glucose, di-O-galloyl-glucose, glucopyranosyl-galloyl-glucose, coumaroyl-O-galloyl-glucose, trimer of catechin, catechin gallate, catechin-glucopyranoside, carboxyl-chrysophanol-O-glucose and emodin-O-glucose. The predominant components identified in the fraction were rhubarb tannins, except for two anthraquinone glycosides of low contents. The polyphenolic analysis also showed the occurrence of abundant tannins. So, the antidiarrhoeal basis of rhubarb was primarily proposed as tannin-related compounds.