title: Determination of p-aminobenzoic acid and its metabolites in rabbit plasma by high-performance liquid chromatography with fluorescence detection.
abstract: A simple, accurate and sensitive high-performance liquid chromatographic method with fluorescence detection was used for measuring plasma concentrations of p-aminobenzoic acid (PABA) and its three metabolites: p-acetaminobenzoic acid (PAABA), p-aminohippuric acid (PAHA) and p-acetaminohippuric acid (PAAHA). A Cosmosil MS-C18 column (250 x 4.6 mm, 5 microns) was used under temperature control at 40 degrees C. The mobile phase was H2O-CH3CN-CH3COOH (100:3:1, pH 4.0) with a flow-rate of 1.5 ml/min. The excitation and emission wavelengths for fluorescence detection were set at 270 and 350 nm, respectively. Plasma samples (200 microliters) were acidified by the addition of 150 microliters of 1 m HClO4 solution containing salicylic acid (SA) as the internal standard. After centrifugation, 30 microliters of the supernatant were injected onto the column. Using this method, PABA and its three metabolites could be determined within 25 min. Within the investigated concentration ranges of PABA (0.1-50 micrograms/ml), PAABA (0.2-50 micrograms/ml), PAHA (0.1-50 micrograms/ml) and PAAHA (0.5-50 micrograms /ml), good linearity (r > 0.99) for the standard curves was obtained. The validation of this method showed coefficient of variance (C.V.) that was well below 15% for all compounds. After intravenous (i.v.) administration of PABA (20 mg/kg) to rabbits (n = 7), PABA followed a one-compartment open model elimination with a half-life of 10.90 +/- 1.03 min. The mean half lives for PAABA, PAHA and PAAHA were 24.61 +/- 6.42, 12.81 +/- 6.04 and 11.27 +/- 2.77 min, respectively.
authors.affiliation: Department of Pharmaceutics, School of Pharmacy, Taipei Medical College, Taiwan.
authors.forename: D J
authors.initials: DJ
authors.lastname: Song
authors.forename: K Y
authors.initials: KY
authors.lastname: Hsu
mesh_terms: D010129:4-Aminobenzoic Acid / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D000818:Animals; D001711:Biotransformation; D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D006207:Half-Life; D007202:Indicators and Reagents; D007275:Injections, Intravenous; D008297:Male; D011786:Quality Control; D011817:Rabbits; D012015:Reference Standards; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D007202:Indicators and Reagents; D010129:4-Aminobenzoic Acid