A LC-MS-based serum pharmacochemistry approach to reveal the compatibility features of mutual promotion/assistance herb pairs in Xijiao Dihuang decoction.

Xijiao Dihuang decoction (XDT), a famous formula, was usually used to improve the prognosis of patients with blood-heat and blood-stasis syndrome-related diseases. There were some mutual promotion and mutual assistance herb pairs in XDT. However, the exact functions of these herb pairs in the compatibility of XDT were not elucidated due to the lack of appropriate methodologies. Based on the theory of serum pharmacochemistry, a systematic method was established for the qualitative and quantitative analysis of characteristic components in the extracts and drug-containing plasma samples of XDT and its relational mutual promotion/assistance herb pairs. For qualitative analysis, 85 characteristic components were identified using the liquid chromatography with triple time-of-flight mass/mass spectrometry (LC-Triple QTOF-MS/MS) based on the mass defect filtering, product ion filtering, neutral loss filtering and isotope pattern filtering techniques. For quantitative detection, a relative quantitation assay using an extract ion chromatogram (EIC) of the full scan MS experiment was validated and employed to assess the quantity of the 85 identified compounds in the test samples of single herb, herb pairs and XDT. The results of multivariate statistical analyses indicated that both the assistant and guide herbs could improve the solubilization of active compounds from the sovereign and minister herbs in XDT in vitro, might change the trans-membrane transportation, and regulate metabolism in vivo. The methods used in present study might be also valuable for the investigation of multiple components from other classic TCM formulas for the purpose of compatibility feature study.