title: Development of an HPLC-fluorescence determination method for carboxylic acids related to the tricarboxylic acid cycle as a metabolome tool.
abstract: We report the simultaneous determination of the carboxylic acids related to the tricarboxylic acid (TCA) cycle, which plays an important role in producing adenosine triphosphate (ATP) and generating energy in mitochondria. Seven carboxylic acids from the TCA cycle, and pyruvic acid and 2-methylsuccinic acid, as an internal standard, were derivatized with a fluorescent reagent for carboxyl groups, 4-N,N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ), in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 4-N,N-dimethyaminopyridine as the coupling reagents, at 60 degrees C for 120 min. Subsequently, the excess DBD-PZ was removed efficiently using a cation-exchange cartridge, SDB-RPS (Empore). These fluorescent derivatives were separated well from each other on an octadecyl silica column (TSKgel ODS-80Ts, 250 x 4.6 mm, i.d.) with an eluent of acetonitrile-water containing 1% formic acid at a flow rate of 0.8 mL/min, and were detected fluorometrically at 560 nm, with excitation at 450 nm. The validation data were satisfactory in the range of 2.5-100 microm citric acid, isocitric acid, 2-oxoglutaric acid, succinic acid and fumaric acid. The detection limit (S/N = 3) for citric acid was 2 fmol on the column. The structures of these derivatives were confirmed by high-performance liquid chromatography-mass spectrometry, which proved that their carboxylic groups were completely labeled with DBD-PZ, except for oxaloacetic acid. This HPLC method was successfully applied to the analysis of TCA cycle metabolites in rat urine. The method will also be useful for metabolome research, such as for target analyses of metabolites with carboxyl groups, not only in urine but also in cells and organs.
authors.affiliation: Laboratory of Bio-Analytical Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kubota
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fukushima
authors.forename: Reiko
authors.initials: R
authors.lastname: Yuji
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyano
authors.forename: Kazuo
authors.initials: K
authors.lastname: Hirayama
authors.forename: Tomofumi
authors.initials: T
authors.lastname: Santa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Imai
mesh_terms: D000818:Animals; D002264:Carboxylic Acids / Q000032:analysis* / Q000652:urine; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D002952:Citric Acid Cycle; D005456:Fluorescent Dyes / Q000737:chemistry; D008297:Male; D010069:Oxadiazoles / Q000737:chemistry; D010879:Piperazines / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D013050:Spectrometry, Fluorescence / Q000379:methods; D021241:Spectrometry, Mass, Electrospray Ionization; D013449:Sulfonamides / Q000737:chemistry
chemical_list: D002264:Carboxylic Acids; D005456:Fluorescent Dyes; D010069:Oxadiazoles; D010879:Piperazines; D013449:Sulfonamides; C076762:4-(N,N-dimethylaminosulphonyl)-7-(1-piperazinyl)-2,1,3-benzoxadiazole