Mean plasma concentration-time profiles of hispid and homoplantaginin after oral administration of homoplantaginin.
The purpose of the present paper was to study the pharmacokinetic characteristics of homoplantaginin, a major active ingredient of Salvia plebeia R.Br. In this study, the effective partition coefficient, in situ absorption in rat intestinal segments and in vitro biotransformation of homoplantaginin by rat intestinal bacteria were determined. In addition, homoplantaginin was administered to rats by intravenous, peritoneal injection and oral administration. The concentrations of homoplantaginin and hispidulin, a metabolite of homoplantaginin, were determined by a validated highperformance liquid chromatographic (HPLC) assay. After intravenous, peritoneal injection, the concentration of hispidulin could not be determined. In contrast, after oral administration, hispidulin and homoplantaginin were simultaneous quantified, homoplantaginin was rapidly absorbed (Tmax = 16.00 ± 8.94 min), reaching a mean Cmax between 0.77 and 1.27 nmol/mL. The absolute oral bioavailability was calculated to be only 0.75%, and the area under curve (AUC) of hispidulin was about 5.4 times than that of homoplantaginin. The poor oral bioavailability may be attributed to the biotransformation of homoplantaginin by rat intestinal bacteria.