Simultaneous determination of bioactive components of Radix Angelicae Sinensis–Radix Paeoniae Alba herb couple in rat plasma and tissues by UPLC–MS/MS and its application to pharmacokinetics and tissue distribution

A highly sensitive and rapid ultra performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) has been developed and validated for simultaneous quantification of seven components in rat plasma and five components in rat tissues after oral administration of the extracts of different combination Radix Angelicae Sinensis–Radix Paeoniae Alba herb couple and has been applied to compare the different pharmacokinetics and tissue distribution properties of these bioactive components. The extracts of Radix Angelicae Sinensis (RAS), Radix Paeoniae Alba (RPA) and Radix Angelicae Sinensis–Radix Paeoniae Alba herb couple (RRHC) were orally administrated to rats, respectively. The concentrations of ferulic acid, caffeic acid, vanillic acid, ligustilide, paeoniflorin, albiflorin and oxypaeoniflorin in rat plasma and the concentrations of ferulic acid, vanillic acid, paeoniflorin, albiflorin and oxypaeoniflorin in tissues were determined by UPLC–MS/MS. The plasma samples were pretreated by protein precipitation with methanol and the tissue samples were homogenated with water and pretreated by protein precipitation with methanol. Chromatographic separation was performed on a C18 column using 0.1% formic acid–acetonitrile as mobile phase for gradient elution. A triple quadrupole (TQ) tandem mass spectrometry equipped with an electrospray ionization source was used as detector operating both in positive and negative ionization mode and operated by multiple-reaction monitoring (MRM) scanning. Noncompartmental pharmacokinetic parameters were calculated by DAS 2.0 program. The differences between each group were compared by SPSS 16.0 with Independent-Samples T-test. The pharmacokinetic parameters (such as Cmax, Tmax, T1/2, AUC0–T, MRT0–T, Vz/F or CLz/F) of all the detected components between the single herb (RAS or RPA) and herb pair (RRHP) showed significant differences (P < 0.05). It indicated that the compatibility of RAS and RPA could alter the pharmacokinetics features of each component. Tissue distribution results showed that ferulic acid, vanillic acid, paeoniflorin, albiflorin and oxypaeoniflorin mostly distributed in liver and kidney both in herb couple and single herb distributed most in liver and kidney. Compared with single herb, RRHC could increase or decrease the concentrations of five components at different time points compared with the sing herb. The results indicated the method was successfully applied to the comparative study on pharmacokinetics and tissue distribution of different combination of RRHC in rats. The compatibility of two Chinese herbs could alter the pharmacokinetics and tissue distribution properties of major bio-active components in the single herb. The results might be helpful for further investigation of compatibility mechanism of RRHC.