Semi-quantitative determination of monocarboxylate forms of ginkgolide B in plasma by UPLC-MS

Abstract

Ginkgolide B (GB) has a unique structure incorporating three γ-lactones that may be hydrolyzed in aquae as carboxylate forms. However, the determinations of them are challenging because there is no way to prepare the standards of any hydrolyzed products of GB in the solid state. In this report, a semi-quantitative method was developed to determine the monocarboxylate forms of GB in plasma. UPLC coupled with selected ion monitoring (SIR) of m/z 423 and m/z 441 were employed to detect the trilactone and monocarboxylates in assistances with the frozen method and the recovered method, which were, respectively, used to stabilize the hydrolyzed states and fully recover the monocarboxylates as the trilactone in samples. Two monocarboxylates were detected in pH 7.4 potassium phosphate buffers (PPB) after incubations, while only one was found in plasma in vitro and in vivo. The identifications of them require further studies. Following the bioanalytical validation of the trilactone, critical issues of the relative responses of the monocarboxylates in contrast to the trilactone, matrix effects, and stabilities were carefully investigated with subtly designed measures. The validation results supported the quantifications of monocarboxylates in PPB or plasma directly by using the corresponding calibration curve of the trilactone. The applications of this method presented a clear disparity between the hydrolysis kinetics of GB in plasma and PPB. Based on the quantification results and method applications, it was concluded that the present method was suitable to study the complex hydrolysis mechanisms of GB in vitro and in vivo.