Effects of Gut Microbiota on the Bioavailability of Bioactive Compounds from Ginkgo Leaf Extracts

Ginkgo leaf extract (GLE) is a popular herbal medicine and dietary supplement for the treatment of various diseases, including cardiovascular disease. GLE contains a variety of secondary plant metabolites, such as flavonoids and terpenoids, as active components. Some of these phytochemicals have been known to be metabolized by gut microbial enzymes. The aim of this study was to investigate the effects of the gut microbiota on the pharmacokinetics of the main constituents of GLE using antibacterial-treated mice. The bilobalide, ginkgolide A, ginkgolide B, ginkgolide C, isorhamnetin, kaempferol, and quercetin pharmacokinetic profiles of orally administered GLE (600 mg/kg), with or without ciprofloxacin pretreatment (150 mg/kg/day for 3 days), were determined. In the antibacterial-treated mice, the maximum plasma concentration (C_max) and area under the curve (AUC) of isorhamnetin were significantly (p < 0.05) increased when compared with the control group. The C_max and AUC of kaempferol and quercetin (other flavonol glycosides) were slightly higher than those of the control group, but the difference was not statistically significant, while both parameters for terpenoids of GLE showed no significant difference between the antibacterial-treated and control groups. These results showed that antibacterial consumption may increase the bioavailability of isorhamnetin by suppressing gut microbial metabolic activities.