title: Metabolism of gambogic acid in rats: a rare intestinal metabolic pathway responsible for its final disposition.
abstract: Gambogic acid (GA) is a promising natural anticancer candidate. Although the anticancer activity of GA has been well demonstrated, information regarding the metabolic fate of GA is limited. Previous studies suggested that GA is mainly excreted into intestinal tract in rats through bile after intravenous administration, whereas only traces appeared in the feces, suggesting that GA is metabolized extensively in the intestine. However, there has been no report about the intestinal metabolism of GA either in animals or humans. In this study, large amounts of two sulfonic acid metabolites of GA were found in the feces samples of rats after intravenous administration, and their structures were identified as 10-α sulfonic acid GA and 10-β sulfonic acid GA by comparison of the retention times and spectral data with those of synthesized reference substances using liquid chromatography-diode array detector-tandem mass spectrometry. This rare intestinal metabolic pathway mainly involves Michael addition of the sulfite ion to the 9,10 carbon-carbon double bond of α,β-unsaturated ketone. In addition, a more detailed metabolic profile in rats is proposed, according to the results of in vitro and in vivo studies. It was found that GA can be metabolized by a variety of routes, including monooxidation, hydration, glutathionylation, glucuronidation, and glucosidation in the liver of rats. These findings provide information on the major metabolic soft spot of GA in the intestine and liver of rats, which is not only useful in the future human metabolic study of this compound but also of value in the metabolic studies of GA analogs.
authors.affiliation: Department of Pharmaceutical Analysis, Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Li
authors.initials: L
authors.lastname: Ding
authors.forename: Linlin
authors.initials: L
authors.lastname: Hu
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Qian
authors.forename: Shaohong
authors.initials: S
authors.lastname: Jin
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Sun
authors.forename: Zhenzhong
authors.initials: Z
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Xiao
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000032:analysis / Q000378:metabolism*; D001646:Bile / Q000737:chemistry / Q000378:metabolism*; D001688:Biological Products / Q000032:analysis / Q000378:metabolism*; D005243:Feces / Q000737:chemistry*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000737:chemistry; D008099:Liver / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D008862:Microsomes, Liver; D051381:Rats; D044004:Xanthones / Q000032:analysis / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D001688:Biological Products; D044004:Xanthones; C052659:gambogic acid