Characterization of glutathione conjugates derived from reactive metabolites of seven silymarin isomers. (2nd November 2019)

• Record Type: Journal Article
• Authors: Chen, Yan; Yu, Jing; Wang, Xu; Li, Hui; Mao, Xu; Peng, Ying; Zheng, Jiang
• Is Part Of: Xenobiotica. Volume 49:Number 11(2019:Nov.)
• Page Start: 1269
• Page End: 1278
• Publication Date: 2019-11-02
• Subjects: Silymarin isomers -- P450 -- bioactivation -- metabolite profile -- glutathione conjugates; Metabolism -- Periodicals; Drugs -- Physiological effect -- Periodicals; Food additives -- Periodicals; Chemicals -- Physiological effect -- Periodicals; Biochemistry -- Periodicals; Pharmaceutical Preparations -- metabolism -- Periodicals; Metabolism -- Periodicals; 574.133
• DOI: 10.1080/00498254.2018.1549340
• Languages: English
• ISSNs: 0049-8254

Abstract

Abstract: 1. Silymarin refers to a class of flavonoid lignans occurring in the fruits and seeds of the Silybum manalttlm (L). Gaertn, and is widely used in dietary supplements. 2. The main active ingredients of silymarin are silychristins A and B, silydianin, silybins A and B, and isosilybins A and B. However, the metabolism of silymarin has never been investigated. The major objectives of the present study were to investigate the metabolic pathways of silymarin isomers and to identify reactive metabolites. 3. Fourteen glutathione (GSH) conjugates were detected in rat/human liver microsomes incubations containing NADPH, GSH and seven individual isomers. Seven GSH conjugates (M1-M7) resulted from demethylated silymarin. M8-M14 originated from hydroxylated silymarin. Moreover, we found that GSH was probably conjugated on either ring A or ring E of silymarin based on the mass spectrometric fragments. In addition, recombinant enzyme incubation experiments demonstrated that CYP3A4 was the predominant P450 responsible for the metabolism of silymarin. 4. Several P450 enzymes were reportedly inactivated by some of bioactive constituents of silymarin to some extent. Our findings facilitate the understanding of mechanisms of the reported inactivation of P450 enzymes induced by silymarin.