Production of oridonin‐rich extracts from Rabdosia rubescens using hyphenated ultrasound‐assisted supercritical carbon dioxide extraction

BACKGROUND Among active components in Rabdosia rubescens, oridonin has been considered a key component and the most valuable compound because it has a wide range of activities beneficial to human health. To produce a high‐quality oridonin extract, an alternative hyphenated procedure involving an ultrasound‐assisted and supercritical carbon dioxide (HSC‐CO2) extraction method to extract oridonin from R. rubescens was developed in this study. Fictitious solubilities of oridonin in supercritical CO2 (SC‐CO2) with ultrasound assistance were measured by using the dynamic method at temperatures ranging from 305.15 K to 342.15 K over a pressure range of 11.5 to 33.5 MPa. RESULTS Fictitious solubilities of oridonin at different temperatures and pressures were over the range of 2.13 × 10−6 to 10.09 × 10−6 (mole fraction) and correlated well with the density‐based models, including the Bartle model, the Chrastil model, the Kumar and Johnston model and the Mendez‐Santiago and Teja model, with overall average absolute relative deviations (AARDs) of 6.29%, 4.39%, 3.12% and 5.07%, respectively. CONCLUSION Oridonin exhibits retrograde solubility behaviour in the supercritical state. Fictitious solubility data were further determined and obtained a good fit with four semi‐empirical models. Simultaneously, the values of the total heat of solution, vaporisation and solvation of oridonin were estimated. © 2016 Society of Chemical Industry