Comparative study on main compounds and hypoglycemic effects of dispensing granules of Coptidis Rhizoma and Scutellaria–Coptis herb couple with traditional decoction

Abstract

Abstract Background The clinical applications of dispensing granules (DG) have increased dramatically. However, it is controversial whether the DG has the same quality and efficacy compared with traditional decoction (TD). In this study, the contents of main compounds, hypoglycemic effects, and potential mechanism of Coptidis Rhizoma (CR) and Scutellaria–coptis (SC), constituted of a 1:1 mixture of CR and Scutellariae Radix (SR), in the forms of TD and DG were compared. Methods The quantitative analysis was performed on an UPLC-PDA method. The 6-weeks-old male db/db mice were used as Type 2 Diabetes Mellitus (T2DM) mouse modle to investigate the antidiabetic effects of CR and SC in TD form (CR TD and SC TD), as well as CR and SC in DG form (CR DG and SC DG). Results The total content of five alkaloids in CR TD ranged from 71.00 to 78.62 mg, whereas in CR DG it ranged from 38.77 to 53.68 mg in CR DG per 1 g of decoction pieces. Compared to CR TD, CR DG exhibited a 36% reduction on average. For SC samples, the precipitation occurred in the processing of TD but not in the DG, and the relative ratio of alkaloids to flavonoids was determined to be 1:1 in TD and 1:2 in DG. Furthermore, the animal experiments showed that the CR DG (equivalent to 3 g decoction pieces/kg) had almost the same hypoglycemic effect as CR TD when they were administered for 6 weeks. Compared with SC DG (equivalent to 6 g decoction pieces/kg), SC TD showed a better trend in ameliorating T2DM via ameliorating pancreatic structure and function, and activating Akt/AMPK/GLUT4 signaling pathways. Conclusion This study indicated that the contents of main compounds were generally higher in CR TD than CR DG originated from the same raw materials. Additionally, changes in the contents of the primary components validated that the compound interactions are exclusive to SC TD during co-decoction, rather than SC DG. The disparate prossing of SC DG and SC TD caused differences both in chemical composition and hypoglycemic effect, suggesting that the substitutability of DG and TD requires further research.