Optimisation of an Ultrasound‐assisted Extraction Followed by RP‐HPLC Separation for the Simultaneous Determination of Oleanolic Acid, Ursolic Acid and Oridonin Content in Rabdosia rubescens

INTRODUCTION: Rabdosia rubescens is a commonly used herb in traditional Chinese medicine and contains diterpenoids, triterpenoids and various other compounds. Among these components, oridonin, oleanolic acid and ursolic acid have gained considerable interest concerning anti‐cancer activities. However, there is no suitable currently available method for the simultaneous evaluation of these three bioactive compounds in R. rubescens. OBJECTIVE: To develop an optimised ultrasound‐assisted extraction (UAE) method and an efficient HPLC method for the simultaneous evaluation of the three bioactive compounds in R. rubescens. METHODOLOGY: Various parameters that can potentially affect the UAE process were investigated and optimised. HPLC operating conditions were also optimised, and the chromatographic separation was performed on a C18‐column with an acetonitrile–water gradient as the mobile phase. RESULTS: Validation of the HPLC technique developed showed that the method has good linearity, sensitivity, precision and accuracy. The combined UAE–HPLC method was applied to quantitate the amount of oridonin, oleanolic acid and ursolic acid in the plant sample and exhibited good repeatability (RSD (%)