Simultaneous determination of ten flavonoids of crude and wine-processed Radix Scutellariae aqueous extracts in rat plasma by UPLC-ESI-MS/MS and its application to a comparative pharmacokinetic study.

Radix Scutellariae (RS) is a herbal medicine with various pharmacological activities to treat inflammation, respiratory and gastrointestinal infections, etc. In this study, a rapid, sensitive and selective UPLC-ESI-MS/MS method was developed for simultaneous determination of 10 flavonoids - scutellarin, scutellarein, chrysin, wogonin, baicalein, apigenin, wogonoside, oroxylin A-7-O-glucuronide, oroxylin A and baicalin - from RS aqueous extracts in rat plasma with propyl paraben as internal standard (IS). Chromatographic separation was achieved on a C18 column using gradient elution with the mobile phase consisting of methanol and water (containing 0.1% formic acid) at a flow rate of 0.2 mL/min. The detection was performed in multiple reaction monitoring mode using electrospray ionization in negative mode. The validated method showed good linearity over a wide concentration range (r >0.9935). The intra- and interday assay variabilities were <9.5% and <12.4% for all analytes, respectively. The extraction recovery ranged from 71.2 to 89.7% for each analyte and IS. This method was successfully applied to pharmacokinetic comparision after oral administration of crude and wine-processed RS aqueous extracts. There were significant differences in some pharmacokinetic parameters of most analytes between crude and wine-processed RS. This suggested that wine-processing exerted effects absorption of most flavonoids.