Comprehensive Study of In vivo and In vitro Metabolites of Cycloastragenol Based on UHPLC-Q-Exactive Orbitrap Mass Spectrometer.

Background: Cycloastragenol (CAG) is a sapogenin derived from the main bioactive constituents of Astragali Radix (AR). However, the current research on CAG metabolism in vivo and in vitro is still inadequate, and the metabolite cluster is incomplete due to incomplete analysis strategy.

Objective: The objective of this study was to screen and identify the metabolic behavior of CAG in vivo and in vitro.

Methods: A simple and rapid analysis strategy based on UHPLC-Q-Exactive Orbitrap mass spectrometry combined with data-mining processing technology was developed and used to screen and identify CAG metabolites in rat body fluids and tissues after oral administration.

Results: As a result, a total of 82 metabolites were fully or partially characterized based on their accurate mass, characteristic fragment ions, retention times, corresponding Clog P values, and so on. Among the metabolites, 61 were not been reported in previous reports. These metabolites (6 metabolites in vitro and 91 in vivo) were generated through reactions of hydroxylation, glucuronidation, sulfation, hydrogenation, hydroxylation, demethylation, deisopropylation, dehydroxylation, ring cleavage, and carboxyl substitution and their composite reactions, and the hydroxylation might be the main metabolic reaction of CAG. In addition, the characteristic fragmentation pathways of CAG were summarized for the subsequent metabolite identification.

Conclusion: The current study not only clarifies the metabolite cluster-based and metabolic regularity of CAG in vivo and in vitro, but also provides ideas for metabolism of other saponin compounds.