An untargeted metabolomics approach to determine component differences and variation in their in vivo distribution between Kuqin and Ziqin, two commercial specifications of Scutellaria Radix

Kuqin (KQ) and Ziqin (ZQ), derived from the roots of Scutellaria baicalensis Georgi, are two important commercial specifications of Scutellariae Radix (SR, termed Huang qin in Chinese). According to traditional Chinese medicine, KQ is used for the treatment of upper energizer lung heat syndrome while ZQ is used to clear lower energizer large intestine heat syndrome. The chemical basis for differences in efficacy between KQ and ZQ is currently unknown. Here, we present an untargeted metabolomics approach to rapidly screen and identify chemical and in vivo distribution differences between KQ and ZQ. We identified 114 constituent differences between KQ and ZQ, of which 35 were identified in SR for the first time. Furthermore, 19 prototype constituents and 16 metabolites were tentatively identified in rat colon and lungs after oral administration of SR, of which six prototype constituents and 12 metabolites were reported for the first time. Distribution differences of baicalin, wogonoside, wogonin and oroxylin A between colon and lungs were observed. To interpret such differences, their metabolic pathways were proposed. The peak area ratio of baicalin to eriodictyol calculated from the extracted ion chromatogram was proposed as a differentiation index for the classification and quality control of KQ and ZQ. These results may partially explain the efficacy differences between KQ and ZQ, and provide references for clinical treatment of related diseases.