Simple method for rapid quantification of branched-chain 2-oxo acids in physiological fluids as quinoxalinol derivatives by high-performance liquid chromatography

Proton magnetic resonance spectroscopy reflects metabolic decompensation in maple syrup urine disease

Using localized proton magnetic resonance spectroscopy (1H-MRS), accumulation of branched-chain amino acids (BCAA) and their corresponding 2-oxo acids (BCOA) could be non-invasively demonstrated in the brain of a 9-year-old girl suffering from classical maple syrup urine disease. During acute metabolic decompensation, the compounds caused a signal at a chemical shift of 0.9 ppm which was assigned by in vitro experiments. The brain tissue concentration of the sum of BCAA and BCOA could be estimated as 0.9 mmol/l. Localized 1H-MRS of the brain appears to be suitable for examining patients suffering from maple syrup urine disease in different metabolic states.

A convenient enzymatic method for the determination of 4-methyl-2-oxopentanoate in plasma: comparison with high performance liquid chromatographic analysis

A simple and rapid spectrophotometric method for the estimation of 4-methyl-2-oxopentanoate in plasma samples by use of NAD+-dependent D-2-hydroxyisocaproate dehydrogenase from Lactobacillus casei ssp. pseudoplantarum is described. It is based on the kinetic measurement of the decrease of NADH absorbance at 334 nm. Applicability is demonstrated by comparative measurement of 4-methyl-2-oxopentanoate content in plasma of patients with maple syrup urine disease by the enzymatic and a reversed phase high performance liquid chromatographic method.

Gas chromatographic determination of oxo- and hydroxycarboxylic acids in serum and urine of diabetic and normal subjects

Oxo- and hydroxycarboxylic acids in serum and urine are metabolites of valine, leucine and isoleucine and products of ketogenesis. They are simultaneously determined in the form of their methyl esters and methyl esters-O-methyloximes by gas chromatography, using internal and external standards. Normal values for the urinary excretion of these amino acid metabolites are between 3 +/- 2 mumole per 24 h (mean +/- standard deviation) for 2-oxoisocaproic acid and 122 +/- 58 mumole per 24 h for 3-hydroxyisobutyric acid. In diabetic ketoacidosis the values are increased by a factor of 2-10. In the urine of diabetic patients under fasting conditions all metabolites are elevated and reach a maximum on about the seventh day of fasting. In the serum only 2-oxoisocaproic acid, 3-oxobutyric acid and 3-hydroxybutyric acid reach elevated levels under fasting conditions.