Metabolism and plasma pharmacokinetics of isoorientin, a natural active ingredient, in Sprague-Dawley male rats after oral and intravenous administration

1. Several pharmacological effects have been revealed on isoorientin, suggesting its potential medicinal prospects. The metabolic and plasma pharmacokinetic profiles of isoorientin were investigated in rats. 2. For intra-gastric gavage, parent drug and three metabolites were detected in urine and feces by HPLC-MS/MS, but only one metabolite was found in plasma and identified as isoorientin 30-or 4'-O-sulfate (M1) according to MS and UV absorbance spectra. 3. After a single i.v. administration of isoorientin (5, 10, or 15 mg/kg B.W.) in rats, linear pharmacokinetic property was observed with favorable terminal half-lives (1.67 +/- 1.32-2.07 +/- 0.50 h). After a single p.o. administration of isoorientin (150 mg/kg B.W.) in rats, plasma isoorientin concentration was low, but the concentration of M1 was comparatively high. Low systemic exposure of oral isoorientin in rats could result from its low aqueous solubility and extensive first-pass metabolism, and plasma concentration of M1 can be used as a biomarker of isoorientin intake. Isoorientin showed low oral bioavailability (8.98 +/- 1.07%), and had about 6% or 45% dose recovery in urine or feces, respectively, 72 h after intra-gastric gavage. 4. These studies are the first to describe the pharmacokinetics of isoorientin via i.v. or p.o. dosing, providing important information for understanding its process in vivo.