Glucuronidation of emodin in human liver and intestinal microsomes

AIM: To investigate the glucuronidation of emodin in human liver and intestinal microsomes,and to elucidate the UDP-glucuronosyltransferase(UGT) isoforms involved in emodin glucuronidation.METHODS: After incubation of emodin using in vitro human liver or intestinal microsomal system,ultra-performance liquid chromatography(UPLC) was utilized to determine the glucuronides of emodin.Mass spectrum(MS) and nuclear magnetic resonance(NMR) were employed to elucidate the structures of metabolite.Screening assays with recombinant human UGTs were used to identify the UGT isoforms involved in the glucuronidation of emodin.RESULTS: Only one metabolite was identified and elucidated to be emodin-O-monoglucuronide.The metabolic behavior of emodin was followed typical monophasic Michaelis-Menten kinetics.Except UGT1A4 and UGT2B17,the other 10 UGTs were determined to participate in the glucuronidation of emodin.CONCLUSION: Emodin-O-monoglucuronide is the only metabolite of emodin in the incubation system of human liver and intestinal microsome.Different microsomes are responsible for the metabolism of emodin in different organs/regions of the digestive system.The glucuronidation of emodin in the intestine contributes significantly to that of emodin in the liver.