Comparative Pharmacokinetics of Baicalin, Wogonoside, Baicalein and Wogonin in Plasma after Oral Administration of Pure Baicalin, Radix Scutellariae and Scutellariae-Paeoniae Couple Extracts in Normal and Ulcerative Colitis Rats

The aim of this study was to investigate the pharmacokinetic profiles of baicalin, wogonoside, baicalein and wogonin after oral administration of pure baicalin, Radix scutellariae and Scutellariae-Paeoniae couple extracts were administered and the pharmacokinetics profiles were compared between normal and ulcerative colitis rats. The plasma concentrations of the four flavonoids were determined by using a simple and rapid high-performance liquid chromatography method. All the rats were divided randomly into two groups (ulcerative colitis and normal groups). Each group contained three subgroups: pure baicalin, Radix scutellariae and Scutellariae-Paeoniae couple extracts subgroup. Each group received oral administration of pure baicalin, Radix Scutellariae and Scutellariae-Paeoniae couple extracts at the same dose of 200 mg/kg baicalin. The results showed that wogonoside, possibily as a methylated product of baicalin, was found in plasma after oral administration of pure baicalin or formulas to rats. Baicalin and wogonoside demonstrated bimodal phenomenon. Baicalin and wogonoside in Scutellariae-Paeoniae couple extract had shown better absorption than which in pure baicalin and Radix Scutellariae extract. Whether oral administration of pure baicalin, Radix Scutellariae or Scutellariae-Paeoniae couple extracts, ulcerative colitis rats showed better absorption than normal rats. For example AUC(0–t) of baicalin were: (41.46 ± 0.62), (59.12 ± 6.42) and (104.87 ± 0.86) (μg/mL)·h in UC groups vs (17.77 ± 0.66), (28.04 ± 4.06) and (49.01 ± 4.61) (μg/mL)·h in normal groups, respectively. The pharmacokinetics properties of the four flavonoids differed between ulcerative colitis and normal rats, including AUC(0–t) and Cmax (p < 0.05).