Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MANDELIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources

A novel electrophilic reagent, 4-(N-chloroformylmethyl-N-methyl)amino- 7-N,N-dimethylaminosulphonyl-2,1,3-benzoxadiazole (DBD-COCl) for fluorometric detection of alcohols, phenols, amines and thiols.

A novel electrophilic reagent for alcohols, phenols, amines and thiols, 4-(N-chloroformylmethyl-N-methyl)amino-7-N,N-dimethylaminosulph onyl-2,1,3- benzoxadiazole (DBD-COCl) was synthesized. The reactivity of the reagent to these nucleophiles was studied using high-performance liquid chromatography (HPLC) with precolumn derivatization techniques. DBD-COCl reacted in benzene solution at the room temperature or 60 degrees C with androsterone (a representative of hydroxyls), (-)-mandelic and D,L-lactic acid (hydroxy acid), estrone (phenol), benzylamine (primary amine), phenetidine (aromatic amine) and alpha-mercapto-N,2-naphthylacetamide (thiol) to give fluorescent products bearing fluorescence wavelengths at between 543 nm and 555 nm (excitation at between 437 nm and 445 nm). The base catalyst, quinuclidine was required to complete the reaction with the nucleophiles except aromatic amines. The reaction solution was subjected to a reversed phase HPLC and the detection limits of the derivatives were at the femto mol range on column.

Alcohols↗

Simultaneous determination of urinary mandelic, phenylglyoxylic, and mercapturic acids of styrene by high-performance liquid chromatography.

We have developed a relatively simple and reproducible HPLC procedure for the determination of urinary metabolites of styrene. Urine samples (pH 2) are extracted with ethyl acetate, the organic layer is evaporated to dryness, and the residues are dissolved in water-methanol (1:1). Samples are analyzed by HPLC with a C18 reversed-phase column and a water (pH 6, 5mM tetrabutylammonium dihydrogen phosphate)-acetonitrile gradient and ultraviolet detection at 225 nm. Using this method, it is possible to determine simultaneously mandelic and phenylglyoxylic acids, N-acetyl-S-(1-phenyl-2-hydroxyethyl)-L-cysteine (M1), and N-acetyl-S-(2-phenyl-2-hydroxyethyl)-L-cysteine (M2). The internal standard is p-hydroxybenzoic acid. Additional validation data are obtained by analysis of urine samples obtained from rats treated with a wide range of styrene doses.

Acetylcysteine↗

Biological monitoring of styrene: a review.

Recent literature about the biological monitoring of styrene-exposed workers is reviewed. Styrene primarily exhibits its toxicity on the central and peripheral nervous systems, although its mutagenicity and chromosome damaging ability also may be relevant. Uptake, transformation and excretion of styrene show that beside the usual biological indicators, such as urinary mandelic and phenylglyoxylic acids (main metabolites), other indicators also may be of interest. These include styrene in expired air, in blood or in urine. Moreover, intermediate or final metabolites such as styrene glycol or mandelic acid in blood also have been proven to be useful in the interpretation of individual values. The most widely used analytical methods for these indicators are gas or high performance liquid chromatography. Correlations between exposure and the different biological indicators mentioned above show that the most reliable indicators are mandelic acid (MA) in urine sampled at the end of the work shift (but not the first day of the week) and the sum of mandelic and phenylglyoxylic acids (MA + PGA) in urine sampled 16 hr after exposure (before the next shift). The biological exposure limit values corresponding to the threshold limit value-time-weighted average (TLV-TWA) of 50 ppm of styrene are 850 mg MA/g creatinine in the end-of-shift sample and 330 mg MA + PGA/g creatinine in the next-morning sample. Other biological indexes, such as styrene glycol (phenyl ethylene glycol) in blood or styrene in urine, look promising but require further research in field situations.

Absorption↗

Styrene, its metabolism and the evaluation of hazards in industry.

The main products of styrene biotransformation excreted in human urine are mandelic and phenylglyoxylic acids. Phenylethylene oxide seems to be the first metabolite; this compound has been reported to be mutagenic and carcinogenic. The polarographic determination of mandelic acid has been used for about 20 years in Czechoslovakia as an exposure test for persons occupationally exposed to styrene. Only single cases of health damage have been reported to be due to styrene exposure during this time. Recently, however, elevated frequencies of chromosomal aberrations in peripheral lymphocytes have been observed in persons exposed to styrene in Czechoslovakia. The amount of phenylethylene oxide that can be formed in the human body during exposure to 50 ppm of styrene in air during a workshift is about 0.7 g. It would be hardly justifiable now to believe that styrene is not carcinogenic and mutagenic in man. The present Czechoslovakian maximum allowable concentration of styrene (200 mg/m3) should be reduced, and the concentration of 50 mg/m3 may be recommended as reasonable at this time. The corresponding biological limit value of mandelic acid might be 300 mg/l of urine from the last 2 h of the workshift.

Air Pollutants↗

Therapeutic doses of cyproheptadine do not inhibit monoamine oxidase in man.

Cypro, a serotonin and histamine antagonist, has been shown to be a moderately potent reversible inhibitor of tissue monoamine oxidase (MAO) obtained from hamsters and rabbits. In the present study, Cypro inhibits MAO obtained from human platelets with the same potency as harmine (Ki = 5 x 10(-5) M). However, when ten normal volunteers received conventional therapeutic doses of Cypro (16 mg/day) for two days, there was no alteration in their urinary excretion of tryptamine, 5-hydroxyindoleacetic acid, 3-methoxy-4-hydroxymandelic acid, epinephrine, or norepinephrine. We conclude that, when used in conventional clinical doses, Cypro does not inhibit MAO in man.

Adult↗