title: Stability of baicalin in biological fluids in vitro.
abstract: The stability of baicalin in buffered aqueous solutions at different pHs and in biological fluids, including plasma, urine and tissue homogenates, were investigated in vitro. Structures of the degradation products of baicalin were elucidated by liquid chromatography-electrospray ion trap mass spectrometry and the degradation mechanism was proposed with the aid of electron paramagnetic resonance spectrometry. The results showed that the degradation of baicalin was pH- and temperature-dependent. The oxidation-reduction reaction intermediated by phenoxyl radicals is the major degradation process for baicalin in plasma and urine in vitro, whereas baicalin mainly undergoes hydrolysis and phase II metabolic pathways when spiked in tissue homogenates. It is found that acidification can stabilize baicalin in urine and plasma (the final pH adjusted to 3.0-4.0), and baicalin is relatively stable in tissues homogenized with methanol.
authors.affiliation: Laboratory of Drug Metabolism and Pharmacokinetics, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenyang 110016, PR China.
authors.forename: Jie
authors.initials: J
authors.lastname: Xing
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Chen
authors.forename: Dafang
authors.initials: D
authors.lastname: Zhong
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000032:analysis* / Q000737:chemistry / Q000493:pharmacokinetics*; D047310:Apigenin / Q000032:analysis; D002138:Calibration; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D002853:Chromatography, Liquid / Q000379:methods*; D004345:Drug Industry / Q000379:methods*; D004574:Electromagnetic Fields; D004578:Electron Spin Resonance Spectroscopy; D005419:Flavonoids / Q000032:analysis* / Q000737:chemistry / Q000493:pharmacokinetics*; D005965:Glucuronates / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010636:Phenols; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013696:Temperature; D013997:Time Factors
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D005419:Flavonoids; D005965:Glucuronates; D010636:Phenols; C484876:scutellarin; C042329:phenoxy radical; C038044:baicalin; D047310:Apigenin