Abstract
Gegen-Qinlian-Tang (GQT), a popular Chinese medicine prescription, consists of Puerariae Radix, Scutellariae Radix, Coptidis Rhizoma, and Glycyrrhizae Radix. This study investigated the pharmacokinetics of GQT in rats and compared the bioavailability between two dosage forms, that is, traditional decoction (TD) and concentrated powder (CP). Rats were given TD and CP of GQT in a crossover design, and blood samples were withdrawn at predetermined time points. The quantitation methods of ten constituents in two dosage forms of GQT and in serum specimen using HPLC were developed and validated in this study. The pharmacokinetic parameters were calculated using noncompartment model. The results showed that daidzein, baicalein, wogonin, berberine, palmatine, and coptisine were not found in the circulation, whereas the sulfates/glucuronides of daidzein, baicalein, and wogonin were the major forms after oral administration of GQT. Comparison between two dosage forms indicated that the AUC0–t of daidzein sulfates/glucuronides after administration of CP was significantly lower than that of TD by 28.9%, whereas the bioavailabilities of baicalin/baicalein and wogonoside/wogonin were comparable between two dosage forms. In conclusion, the major flavonoids of GQT were extensively metabolized into sulfates/glucuronides and present as the major molecules in the circulation. TD of GQT revealed higher bioavailability of daidzin/daidzein than CP.
Highlights
Gegen-Qinlian-Tang (GQT) was a famous prescription firstly described in Shang-Han-Lun and commonly used to treat virus diarrhea, bacillary dysentery, and general fever clinically [1]
GQT is composed of four Chinese herbs, including Puerariae Radix (roots of Pueraria lobata (Willd.) Ohwi, PR), Scutellariae Radix, Coptidis Rhizoma, and honey-processed Glycyrrhizae Radix
Many endogenous sulfates and glucuronides as well as the conjugated metabolites of xenobiotics have been reported as substrates of multidrug resistance-associated proteins (MRPs) [11, 12] and organic anion transporters (OATs) [12, 13]
Summary
Gegen-Qinlian-Tang (GQT) was a famous prescription firstly described in Shang-Han-Lun ( called “treatise on febrile diseases”) and commonly used to treat virus diarrhea, bacillary dysentery, and general fever clinically [1]. Based on recent findings of polyphenol pharmacokinetics, it has been generally recognized that most polyphenols are present predominantly as sulfates/glucuronides rather than their parent forms in the bloodstream [8,9,10]. The alkaloids, such as berberine, coptisine, and palmatine, the constituents of CR, have been reported to be transformed to sulfates and glucuronides after being absorbed and metabolized by dealkylation [10]. This study investigated the pharmacokinetics of GQT in rats and, the relative bioavailability between TD and CP was evaluated
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