Phase II metabolism of asarone isomers in vitro and in humans using HPLC-MS/MS and HPLC-QToF/MS

Hermes, Lena; Römermann, Jannis; Cramer, Benedikt; Esselen, Melanie

Abstract

(1) Background: Metabolism data of asarone isomers, in particular phase II, in vitro and in humans is limited so far. For the first time, phase II metabolites of asarone isomers were characterized and human kinetic as well as excretion data after oral intake of asarone-containing tea infu-sion was determined. (2) Methods: A high pressure liquid chromatography coupled with quadru-pole time-of-flight mass spectrometry (HPLC-qTOF-MS) approach was used to identify phase II metabolites using liver microsomes of different species and in human urine samples. For quantita-tion of the respective glucuronides, a beta-glucuronidase treatment was performed prior to analysis via high pressure liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). (3) Results: Ingested beta-asarone and erythro and threo-asarone diols were excreted as diols and respective diol glucuronide conjugates within 24 h. An excretion rate about 42% was estimated. O-Demethylation of beta-asarone was also indicated as a human metabolic pathway because a corre-sponding glucuronic acid conjugate was suggested. (4) Conclusions: Already reported O-demeth-ylation and epoxide-derived diols formation in phase I metabolism of beta-asarone in vitro was verified in humans and glucuronidation was characterized as main conjugation reaction. The excretion rate of 42% as erythro and threo-asarone diols and respective asarone diol glucuronides suggests that epoxide formation is a key step in beta-asarone metabolism, but further, as yet unknown metabolites should also be taken into consideration. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.