RT Journal Article SR Electronic T1 Metabolism of Echinacoside, a Good Antioxidant, in Rats: Isolation and Identification of Its Biliary Metabolites JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 431 OP 438 DO 10.1124/dmd.108.023697 VO 37 IS 2 A1 Jia, Cunqin A1 Shi, Haiming A1 Jin, Wei A1 Zhang, Ke A1 Jiang, Yong A1 Zhao, Mingbo A1 Tu, Pengfei YR 2009 UL http://dmd.aspetjournals.org/content/37/2/431.abstract AB Echinacoside (ECH) is one of the major active phenylethanoid glycosides (PEGs) in famous traditional Chinese medicine, Herba Cistanches. Although it has various bioactivities, such as antioxidation, neuroprotection, and hepatoprotection, knowledge about its metabolic fate is scant. In the present study, eight phase II metabolites, 3,4-O-dimethyl-ECH-3-O-β-d-glucuronide (M1); 4,4-O-dimethyl-ECH-3-O-β-d-glucuronide (M2); 3,4-O-dimethyl-ECH-4-O-sulfate ester (M3); 4,4-O-dimethyl-ECH-3-O-sulfate ester (M4); 3,3-O-dimethyl-ECH (M5); 3,4-O-dimethyl-ECH (M6); 4,3-O-dimethyl-ECH (M7); and 4,4-O-dimethyl-ECH (M8), were isolated from rat bile sample after intravenous administration of ECH and identified by mass spectra and NMR spectroscopy, including 1H NMR, 13C NMR, nuclear Overhauser effect difference spectroscopy, and two-dimensional NMR (heteronuclear single quantum correlation, heteronuclear multiple-bond correlation spectroscopy, gradient-selected correlation spectroscopy, and nuclear Overhauser effect spectroscopy). Among them, M5 to M8 were O-di-methylated conjugates; M1 and M2 and M3 and M4 were O-dimethyl glucuronides and O-dimethyl sulfates, respectively. In the three types of metabolites of rat, the major metabolites were the methyl ethers and the glucuronides, whereas the sulfates were minor. The regioselectivity of conjugation for ECH and metabolic pathway of ECH were proposed, which gave insight into the mechanism of ECH for its bioactivities in vivo. The American Society for Pharmacology and Experimental Therapeutics