title: Concurrent measurement of unbound genistein in the blood, brain and bile of anesthetized rats using microdialysis and its pharmacokinetic application.
abstract: Genistein, the major isoflavone in soybeans, has been shown to have a wide range of effects. We used an HPLC-UV combined with microdialysis method to detect unbound genistein in rat blood, brain and bile. Genistein dialysates were eluted with a mobile phase containing acetonitrile-water (40:60, v/v, pH 3.5 adjusted by 0.1% acetic acid). Samples were separated using a phenyl (5 microm) column maintained at ambient temperature. The UV detector wavelength was set at 259 nm. The flow rate was 1.0 m/min. The limit of quantitation for genistein was 50 ng/ml. The in vitro recoveries of genistein were 31 +/- 1, 13 +/- 1 and 59 +/- 4% in microdialysis probes of blood, brain and bile, respectively (n = 4). Inter- and intra-assay accuracy and precision of the analysis were less than 10% in the concentration ranges of 0.05-5.0 microg/ml. A small ratio of genistein penetrates the blood-brain barrier (BBB) and goes through hepatobiliary excretion after genistein administration (10 or 30 mg/kg, i.v.). The brain-to-blood (AUC(brain)/AUC(blood)) and bile-to-blood (AUC(bile)/AUC(blood)) distribution ratios were 0.04 +/- 0.01 and 1.85 +/- 0.42, respectively for the dosage of genistein 30 mg/kg. After co-administration of cyclosporine, a P-glycoprotein (P-gp) inhibitor, the distribution ratios of genistein in brain and bile were not significantly altered. These results suggest that the BBB penetration and hepatobiliary excretion of genistein may not regulated by P-gp.
authors.affiliation: National Research Institute of Chinese Medicine, 155-1, Li-Nong Street Section 2, Taipei 112, Taiwan. thtsai@nricm.edu.tw
authors.forename: Tung-Hu
authors.initials: TH
authors.lastname: Tsai
mesh_terms: D000818:Animals; D019540:Area Under Curve; D001646:Bile / Q000737:chemistry*; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D016572:Cyclosporine / Q000737:chemistry; D019833:Genistein / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics*; D008297:Male; D017551:Microdialysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity
chemical_list: D016572:Cyclosporine; D019833:Genistein