Plasma pharmacochemistry combined with microdialysis to screen potential bioactive components and their metabolites in Anemarrhena asphodeloides saponin extract using ultrahigh-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry.

Although various techniques have been employed to analyze drug metabolites, the metabolism of multicomponent herbal medicine has seldom been fully addressed. In contrast to chemical drugs, a number of compounds in herbal medicine could get into circulation and then be metabolized. Metabolism study on active constituents in herbal medicine is a good way for us to explain and predict a variety of events related to the efficacy and toxicity of herbal medicine. The present work aims to elucidate the multicomponent metabolic characteristics of a herbal medicine by the combination of plasma pharmacochemistry and microdialysis sampling. Anemarrhena asphodeloides, a well-known traditional Chinese medicine, was chosen as a model. After oral administration of A. asphodeloides saponin extract to rats, microdialysis samples were collected continuously in the jugular vein and analyzed by ultrahigh-performance LC/quadrupole-TOF MS. The identification of compounds in biosamples was achieved by accurate mass measurement and detailed fragmentation pathway analysis. The results showed that unbound constituents in blood circulation of the rat included seven parent saponins and six metabolites, which might be the potential active components in vivo. Among which, three metabolites have not been previously reported and were identified in this study. It is the first report on systemic metabolism of total saponins of A. asphodeloides in mammalian plasma.