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ETHNOPHARMACOLOGICAL RELEVANCE Yin-Chen-Hao Tang (YCHT), derived from "Treatise on Febrile Diseases" in ancient China, has been a very popular hepatoprotective three-herb formula in China and Japan, although its chemical base remains unclear. AIM OF THIS STUDY As the first step in revealing the hepatoprotective chemical base of YCHT, we aimed to clarify the absorbed ingredients and associated metabolic pathways for orally dosed YCHT in both normal and liver injury rats from a liver-centric perspective. MATERIALS AND METHODS With the aid of 10 reference compounds, the absorbed ingredients and generated metabolites were systematically characterized by high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF) in the portal vein plasma (the plasma before hepatic disposition) - liver - systemic plasma (the plasma after hepatic disposition), following oral administration of YCHT in normal and CCl4-induced liver injury rats. RESULTS A total of 38 compounds with six chemical structures, consisting of 10 prototypes and 28 metabolites generated through 9 biotransformations, were absolutely or tentatively identified, and 25 compounds were first reported on YCHT treatments. Among them, 8 compounds were absolutely confirmed by comparing with standard substances, and some had published hepatoprotective activities. Compared with the 35, 15, and 29 compounds identified in the portal vein plasma, liver, and systemic plasma of normal rats, respectively, the corresponding numbers of characterized compounds were 37, 13 and 29 in the liver injury rats. CONCLUSIONS Sulfation and glucuronidation were the predominant biotransformations, and intestinal metabolism, prior to hepatic metabolism, occurred for most compounds. CCl4-induced liver injury caused only slight changes in the metabolic profiles of rats orally administered YCHT. These results provided the precondition for further quantitative analysis and pharmacodynamic screening of compounds in YCHT.