K-targeted isolation of C-glycosylflavones from Vitex agnus-castus by countercurrent methodology

Abstract

C-glycosylated flavones, including orientin, isoorientin, vitexin, and isovitexin, are minor but biologically significant constituents of fruit extracts of the chaste-tree (Vitex agnus-castus L.), a botanical supplement used to treat PMS and postmenopausal symptoms. The partition coefficient, or K-value, is the ratio of the concentration of a compound in each phase of a biphasic solvent mixture and is a physicochemical property of a particular compound in a particular solvent system. This value can be used to predict retention volume (V ret) in a countercurrent separation procedure. The K-values of C-glycosylflavones present in complex botanical fractions have been determined in a number of solvent system families (HEMWat, EBWat, HterAcWat, terAcWat) using the shake-flask technique combined with relative LC-MS quantification. This K-value database has been used to develop targeted centrifugal partition (CPC) and high-speed countercurrent chromatography (HSCCC) methods. In each separation procedure the actual K value and V ret was reasonably predicted by the shake-flask partition experiment, confirming the utility of this approach in choosing a solvent system and targeting the fraction that contains the desired compound. This K-value database allowed for the efficient isolation of C-glycosylflavones from V. agnus-castus using orthogonal CCC and CPC methods.