Kinetics of reactive extraction of equol enantiomers from organic phase by hydroxypropyl-β-cyclodextrin

This paper reports on the kinetics of the reactive extraction of equol (EQU) enantiomers from the organic phase to the aqueous phase by hydroxypropyl-β-cyclodextrin (HP-β-CD). Theory of extraction accompanied by a chemical reaction was employed to achieve an insightful understanding of the extraction process. Important factors affecting the extraction rate were investigated, including stirring speed, interfacial area, pH value of aqueous phase, initial enantiomers concentration in organic phase as well as the concentration of HP-β-CD in aqueous phase. The experimental results demonstrate that the extraction reaction is a fast reaction. The reactions are first order in EQU and second order in HP-β-CD with forward rate constants of 3.08 × 10−4 m6 mol−2 s−1 for R-EQU and 2.72 × 10−4 m6 mol−2 s−1 for S-EQU, respectively.