Hypoglycemic ingredients identification of Rheum tanguticum Maxim. ex Balf. by UHPLC-triple-TOF-MS/MS and interrelationships between ingredients content and glycosidase inhibitory activities

Rheum tanguticum Maxim. ex Balf. (RT), mainly is mainly produced in Gansu, Qinghai, Tibet and Sichuan of China, has long been used as a medicine for purging fire and quenching thirst. The RTR-2 (Rheum tanguticum root extract without polysaccharides and protein) had strong inhibitory activities against a-amylase, maltase and sucrase with the IC50 0.042 mg/mL, 0.124 mg/mL and 0.097 mg/mL, respectively. In addition, RTR-2 could significantly reduce PBG level of diabetic mice in starch/maltose/sucrose tolerance test. Total 48 constituents including 12 anthraquinones, 4 bianthmnes, 8 flavans, 3 stilbenes, 5 phenylbutanones, 4 naphthosides, 8 glucose gallates and 4 phenolic acids were determined in RTR-2 by UPLC-Triple-TOF/MS analysis of molecular ion, main fragments, retention time, and references. Furthermore, the components such as flavan ((-)-epicatechin 3-O-gallate) and phenylbutanone (lindleyin) were demonstrated to have sucrase and maltase inhibitory activites, and might be the main hypoglycemic active ingredients of RTR-2 extract. All these results offered an exhaustive knowledge for the hypoglycemic compounds of Rheum tanguticum, which was conducive to its further development and utilization as a valuable source of hypoglycemic plant in pharmaceutical industry.