Urinary Pharmacokinetics of Baicalein, Wogonin and Their Glycosides after Oral Administration of Scutellariae Radix in Humans

Baicalin, baicalein, wogonoside and wogonin are flavone constituents of Scutellariae Radix with various beneficial biological activities. The purpose of this study was to investigate the urinary pharmacokinetics of these flavones after oral administration of Scutellariae Radix commercial powder. Ten healthy male volunteers received a dose of 5.2 g commercial powder (comparable to 9 g crude drug), respectively. The concentrations of baicalin, baicalein and wogonin in the commercial powder as well as their metabolites in urine were assayed by HPLC method. The glucuronides and sulfates of baicalein and wogonin in urine were hydrolyzed with β-glucuronidase and sulfatase, respectively. Our results showed that the mean cumulated renal excretion of baicalein glucuronides and sulfates were 43.1±4.5 μmol (2.9% of dose) and 64.8±6.3 μmol (4.3% of dose), respectively, whereas wogonin glucuronides and sulfates were 21.6±2.0 μmol (5.9% of dose) and 20.7±1.7 μmol (5.7% of dose), respectively. The result indicated that the renal excretion of conjugated metabolites of wogonin (11.6% of dose) were higher than that of baicalein (7.2% of dose). The baicalein sulfates was predominant than the corresponding glucuronides, whereas wogonin sulfates was comparable to the corresponding glucuronides.