Isolation, identification and antiviral activities of metabolites of calycosin-7-O-β-d-glucopyranoside

In vivo and in vitro metabolites of calycosin-7-O-β-d-glucopyranoside in rats were identified using a specific and sensitive high performance liquid chromatography–tandem mass spectrometry (HPLC–MSn) method. The parent compound and twelve metabolites were found in rat urine after oral administration of calycosin-7-O-β-d-glucopyranoside. The parent compound and six metabolites were detected in rat plasma. In heart, liver, spleen, lung and kidney samples, respectively, six, eight, seven, nine and nine metabolites were identified, in addition to the parent compound. Three metabolites, but no trace of parent drug, were found in the rat intestinal flora incubation mixture and feces, which demonstrated cleavage of the glycosidic bond of the parent compound in intestines. The main phase I metabolic pathways of calycosin-7-O-β-d-glucopyranoside in rats were deglycosylation, dehydroxylation and demethylation reactions; phase II metabolism included sulfation, methylation, glucuronidation and glycosylation (probably). Furthermore, two metabolites commonly found in rat urine, plasma and tissues were isolated from feces and characterized by NMR. The antiviral activities of the metabolite calycosin against coxsackie virus B3 (CVB3) and human immunodeficiency virus (HIV) were remarkably stronger than those of calycosin-7-O-β-d-glucopyranoside.