Influence of Coptis Chinensis on pharmacokinetics of flavonoids after oral administration of Radix Scutellariae in rats

Radix Scutellariae (RS) and Coptis Chinensis (CC) are the most popular components in traditional Chinese medicine prescriptions. Flavonoids are the main effective ingredients in RS and berberine is the main effective ingredient in CC. The aim of this study was to determine the influence of CC on the pharmacokinetics of flavonoids following the administration of RS in rats and to investigate the effects of CC on the pharmacokinetic mechanism. Rats were administered RS or RS+CC by intragastric gavage (i.g.). Plasma concentrations of baicalin (baicalein 7-glucuronide) and wogonoside (wogonin 7-glucuronide) were measured by HPLC. Pharmacokinetic parameters were calculated from the plasma concentration time curve. The effect of CC on the metabolism of flavonoids in RS by rat intestinal flora was studied using rat fecal suspensions after ig administration of CC. The effect of berberine on the bi-directional transport of baicalein and baicalin was studied in Caco-2 monolayer models. The effect of CC on the metabolism of baicalein and baicalin by the liver was studied using rat liver microsomes after i.g. administration of CC. Compared to RS alone, RS+CC decreased AUC and C(max) of baicalin and wogonoside. CC decreased the hydrolyzation of baicalin and wogonoside by intestinal flora. Berberine decreased the amount of baicalein transported to the basolateral side and the amount of baicalin which appeared at the basolateral side. The results showed that CC may decrease the bioavailability of baicalin and wogonoside in RS and the mechanism was related to CC decreasing the transport of flavonoid aglycones from the mucosa side to the serosal side and the hydrolyzation of flavonoids by inhibiting intestinal flora.