Study on extraction kinetics of Salviae Miltiorrhizae Radix et Rhizoma: model establishment and investigation of critical process parameters

Abstract

In this study, Fick's first law and partition equilibrium were used to represent the internal and external mass transfer processes of Salviae Miltiorrhizae Radix et Rhizoma at the macroscopic level, and a mass transfer model was established. The specific surface area was integrated into the mass transfer resistance, which effectively avoided the irregular shape of medicinal materials and expanded the application scope of the model. Meanwhile, the mass transfer model was further combined with the kinetic model of salvia-nolic acid degradation to establish the extraction kinetic models of salvianolic acid B, lithospermic acid and Danshensu. The model was applied to study the extraction process of Salviae Miltiorrhizae Radix et Rhizoma. According to the sensitivity analysis results, the relative error of the model prediction was within 5% near the maximum extraction rate(320 min), and the prediction performance of the model was good. According to the investigation results of different process parameters, stirring could significantly accelerate the mass transfer rate of salvianolic acid B, while the mass transfer resistance and degradation rate constant were not affected by solvent-to-solid ratio. The linear relationship between the reciprocal of temperature and the logarithm of mass transfer resistance was good(R~2=0.996), indicating that the temperature and mass transfer resistance conformed to Arrhenius formula. In addition, we also found that the concentration changes of lithospermic acid and Danshensu were weakly affected by mass transferwhen the extraction temperature was higher than 358 K. This study has provided the basis for the process optimization and quality control of traditional Chinese medicine extraction.