To establish an HPLC-MS/MS method for the simultaneous determination of six characteristic components of Scutellariae Radix including baicalein, baicalin, wogonin, wogonoside, chrysin and oroxylin A in rat plasma, and to compare their pharmacokinetic profiles after oral administration of Scutellariae Radix and Niuhuang Jiedu tablets (NHJDT) to rats.

Rats were given 250 mg·kg^-1 of NHJDT suspension or the prescribed equivalent amount of Scutellariae Radix aqueous extract, and plasma samples were collected at different time intervals. Naringenin was used as internal standard. After precipitated with methanol, the plasma samples were separated on an Inertsil C₈-3 (150 mm×4.6 mm, 5 μm) column by linear gradient elution with 0.1% formic acid solution(A)-0.1% formic acid-methanol(B) as mobile phase. The flow rate was 1.0 mL·min^-1, and the column temperature was 35 ℃. The analytes were detected by tandem mass spectrometry with the electrospray ionization (ESI) source combined with multiple reaction monitoring(MRM) mode in positive ion mode. The pharmacokinetic parameters were calculated and statistically analyzed.

The six characteristic components of Scutellariae Radix were all in good linear relationships in the range of 5-500 ng·mL^-1. The RSDs for accuracy test were in the range of 88.43%-108.6%, and the RSDs for inter-batch and intra-batch precision tests were all below 15%. The matrix effect and plasma stability met the requirements of methodology validation in biological sample analysis. Baicalin and wogonoside were the major components detected in rat plasma after oral gavage of Scutellariae Radix aqueous extract and NHJDT suspension. The AUC_0-t of wogonoside was significantly increased in NHJDT group compared with Scutellariae Radix group. Furthermore, the C_max of wogonoside and baicalin were significantly increased while the T_max was decreased after NHJDT suspension administration.

This method is specific and sensitive for the determination of six characteristic components of Scutellariae Radix, and suitable for pharmacokinetic study of rat plasma. NHJDT with co-existing components enhances the absorption and influences the pharmacokinetic behaviors of active ingredients of Scutellariae Radix.