title: An accurate and reproducible method for the quantitative analysis of isoflavones and their metabolites in rat plasma using liquid chromatography/mass spectrometry combined with photodiode array detection.
abstract: To study the safety and potential health benefits of soy isoflavones, a rapid and simple method based on liquid chromatography combined with mass spectrometry (LC/MS) and photodiode array detector (PDA) was developed for the determination of isoflavones in rat plasma. The analytes included daidzein, genistein, glycitein, equol, 4-ethyl phenol, and biochanin A over a concentration range of 1.0-4320.0 nM using 75 microL of rat plasma. Rat plasma samples were hydrolyzed by adding an enzyme mixture from Helix pomatia containing glucuronidase and sulfatase to convert the isoflavone beta-glycosides daidzin, genistin, and glycitin to their active aglycone forms. A liquid-liquid extraction method using ethyl acetate as the extraction solvent was used to extract aglycones and the internal standards (phenolphthalein beta-D glucuronide, 4-methylumbelliferyl sulfate, and apigenin) from digested plasma samples. The extract was evaporated to dryness under a nitrogen stream, reconstituted with 0.1% formic acid in water-acetonitrile (85 + 15), and injected into a Zorbax SB-CN reversed-phase column (4.6 x 75 mm, 3.5 microm particle size). The Micromass ZQ detector was operated in the positive ion selected-ion monitoring mode. The flow rate for LC was 1.0 mL/min, with a split where 25% of the effluent was introduced into the electrospray ionization probe of the MS instrument and 75% into the PDA. The chromatographic run time was 16.0 min, with delay of 10 min/injection. The interday precision and accuracy of the standard samples were <2.6% relative standard deviation and <10% relative error, respectively. Recovery of the reported isoflavones with this method varied from 86 to 100%.
authors.affiliation: Health Canada, Health Products and Food Branch, Nutrition Research Division, Banting Research Centre, Tunney's Pasture, Ottawa, Ontario, Canada K1A OL2.
authors.forename: Estatira
authors.initials: E
authors.lastname: Sepehr
authors.forename: Patrick
authors.initials: P
authors.lastname: Robertson
authors.forename: G Sarwar
authors.initials: GS
authors.lastname: Gilani
authors.forename: Gerard
authors.initials: G
authors.lastname: Cooke
authors.forename: Benjamin Pui-Yan
authors.initials: BP
authors.lastname: Lau
mesh_terms: D000085:Acetates / Q000032:analysis; D000818:Animals; D002138:Calibration; D002845:Chromatography; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid / Q000379:methods*; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D006372:Helix, Snails; D006868:Hydrolysis; D007529:Isoflavones / Q000032:analysis* / Q000097:blood*; D013058:Mass Spectrometry / Q000379:methods*; D051381:Rats; D015203:Reproducibility of Results; D012997:Solvents
chemical_list: D000085:Acetates; D007529:Isoflavones; D012997:Solvents; C007650:ethyl acetate; D004121:Dimethyl Sulfoxide