Analysis of condensed tannins' constituent units by thiolysis with cysteamine hydrochloride and analysis of thiolysis products' HPLC behavior / 国际药学研究杂志

ABSTRACT

Objective To establish a method of analyzing the structural units of condensed tannins from Chinese patent medicine Wei MaiNing. Methods The ethanol extract of Wei MaiNing capsule was depolymerized in the presence of cysteamine and analyzed by HPLC, and eight major thiolysis products were identified by LC-MS analysis combined with reference sample. Meanwhile, the influence of mobile phases with different pH values on the HPLC behavior of thiolysis products was investgated. Results Eight major thiolysis products were 4β-(2-aminoethylthio)catechin, 4β-(2-aminoethylthio)epicatechin, catechin, 4β-(2-aminoethylthio)epicatechin-3-O-gallate, epicatechin, 4β-(2-aminoethylthio)catechin-3-O-gallate, epicatechin-3-O-gallate and catechin-3-O-gallate. Variation of the pH value had more impact on the retention time of catechins' aminomethylthio derivatives than that of catechins', which led to the changes of chromatographic peaks order. Conclusion The method is simple, reliable, and could be used to determine the structural units of condensed tannins. In order to ensure the stability of derivatives retention time, pH values of mobile phases should be controlled strictly when thiolysis products are analyzed by HPLC.