Metabolism and distribution of two major constituents of ‘Xing-Nao-Jing Injection’—germacrone and curdione in rats

Germacrone and curdione are germacrane-type sesquiterpenoids that are widely distributed and have extensive pharmacological activities; they are the main constituents of ‘Xing-Nao-Jing Injection’ (XNJ). Studies on the metabolic features of germacrane-type sesquiterpenoids are limited. In this study, the metabolites of germacrone and curdione were characterized by UHPLC-Q-Exactive Oribitrap mass spectrometry after they were orally administered to rats. In total, 60 and 76 metabolites were found and preliminarily identified in rats administered germacrone and curdione, respectively, among which at least 123 potential new compounds were included. New metabolic reactions of germacrane-type sesquiterpenoids were identified, which included oxidation (+4 O and +5 O), ethylation, methyl-sulfinylation, vitamin C conjugation, and cysteine conjugation reactions. Among the 136 metabolites (including 113 oxidation metabolites, two glucuronidation, two methylation, nine methyl-sulfinylation, three ethylation, six cysteine conjugation, and one Vitamin C conjugation metabolites), 32 metabolites were detected in nine organs, and the stomach, intestine, liver, kidneys, and small intestine were the main organs for the distribution of these metabolites. All 136 metabolites were detected in urine and 64 of them were found in feces. The results of this study not only contribute to research on in vivo processes related to germacrane-type sesquiterpenoids but also provide a strong foundation for a better understanding of in vivo processes and the effective forms of germacrone, curdione, and XNJ.