An In Vitro Dissolution Determination of Multi-Index Components in Tibetan Medicine Rhodiola Granules

The composition of the Tibetan medicine Rhodiola granules (RG) is complex, and the overall quality of RG is difficult to determine. Therefore, establishing a method to determine the multi-component in vitro dissolution of RG is of great significance for quality control. This study uses the second paddle method of the fourth general rule 0931 from the Chinese Pharmacopoeia (2020 edition), compliant with apparatus 2 of the United States Pharmacopeia (USP). The dissolution apparatus was set to a rotation speed of 100 rpm with ultrapure water as the dissolution medium. A sample volume of 1 mL was collected at each timepoint. Furthermore, the cumulative dissolution of gallic acid, salidroside, and ethyl gallic acid in RG at different time points was determined by high-performance liquid chromatography (HPLC). Finally, the dissolution curves were drawn, and the curves were fitted to the GompertzMod, the Gompertz, the Logistic, and the Weibull equations. The results showed that the cumulative dissolution of gallic acid in RG was over 80% at 1 min, the cumulative dissolution of salidroside and ethyl gallic acid was over 65% at 5 min, and the cumulative dissolution of each index component decreased after 30 min. The curve fitting demonstrated that the GompertzMod equation was the best-fitting model for each index component of RG. In conclusion, the dissolution test method described in this protocol is simple, accurate, and reliable. It can characterize the dissolution behavior of the index components in RG in vitro, which provides a methodological reference for quality control of RG and quality evaluation of other ethnic compounds.