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At least 19 recordsLinked to original sources
PubMed1975

Intermediates in the metabolism of m-carboxy-substituted aromatic amino acids in plants. Phenylpyruvic acids, mandelic acids, and phenylglyoxylic acids.

Tracer experiments with 14C-labelled precursors in Iris times hollandica cv. Wedgwood, Reseda Iutea L. And Keseda Odorata L. have demonstrated that 3-(3-carboxyphenyl) alanine and 3-(3-carboxy-4-hydroxyphenyl) alanine can be derived from the corresponding pyruvic acids, presumably by unspecific transaminations, and that (3-carboxyphenyl) glycine and (3-carboxy-4-hydroxyphenyl) glycine can be derived from the corresponding phenylglyoxylic acids. The glycine derivatives are derived from the alanine derivatives, and the corresponding mandelic acids are intermediates in these transformations. The corresponding phenylacetic acids are incorporated only slightly into the glycine derivatives, indicating that oxidation at the benzylic position in the C6-C3 compounds takes place early in the transformation. The corresponding cinamic acids are not metabolized at all in the plants.

Alcohols↗
PubMed1977

Isotachophoretic analysis of mandelic acid, phenylglyoxylic acid, hippuric acid and methylhippuric acid in urine after occupational exposure to styrene, toluene and/or xylene.

A simple, rapid and sensitive analytical method has been developed for the determination of phenylglyoxylic acid, mandelic acid, hippuric acid and methylhippuric acid; 0-, m- and p-methylhippuric acids are partly separated. These compounds are found as metabolites after occupational exposure to styrene, toluene and xylene. The method has been applied successfully to samples extracted from human urine by diethyl ether. The method can be used to accurately and simultaneously determine as little as 0.5 nmole of all of these acids in less than 20 min.

Chromatography, Gas↗
PubMed1976

Reaction pathways of in vivo stereoselective conversion of ethylbenzene to (-)-mandelic acid.

1. Mandelic acid formed in vivo from ethylbenzene as well as from various oxidation intermediates was laevo mandelic acid and was of surprisingly high optical purity. 2. Reaction sequences are proposed for the stepwise oxidation of ethylbenzene to mandelic acid. 3. Although the initial hydroxylation of ethylbenzene to methylphenyl-carbinol is stereoselective, the optical activity of mandelic acid is not established at this point since the optical centre is destroyed in the second step, dehydrogenation to acetopheneone. 4. Acetophenone appears to be a precursor of not only mandelic acid and benzoylformic acid but benzoic acid as well. 5. The route from acetophenone involves conversion to omega-hydroxyacetophenone and subsequent reduction to glycol and/or oxidation to phenylglyoxal. 6. The configuration of mandelic acid is determined either during reduction of hydroxyacetophenone or reduction of phenylglyoxal.

Animals↗
PubMed1977

[Determination of the urinary metabolites hydroxyindole-acetic acid, vanillyl mandelic acid and homovanillic acid by means of lipophilic gel chromatography and gas chromatography (author's transl)].

A specific and practicable method is described for the quantitative determination of urinary phenol- and indole-carboxylic acids. High specificity is achieved by a preliminary separation of the free acids (extracted from the urine sample) with the aid of organophilic gel chromatography on Sephadex LH 20, followed by gas chromatographic analysis of the silyl derivatives of the acids. The organophilic gel chromatography of the free acids shows a high recovery rate in the micro- and submicrogram range. The difficulties encountered in other techniques in the derivatisation and gas chromatographic separation of the individual components are avoided by using the preliminary separation, and by using N-methyl-N-trimethylsilyl-trifluoroacetamide for the derivatisation. Use of this preparation technique with a direct read-out gas chromatograph with automatic sample introduction, gives high accuracy and precision, and a facility for the determination of a wide range of aromatic acids in urine.

Chromatography, Gas↗
PubMed1976

Involvement of 4-hydroxymandelic acid in the degradation of mandelic acid by Pseudomonas convexa.

A microorganism capable of degrading DL-mandelic acid was isolated from sewage sediment of enrichment culture and was identified as Pseudomonas convexa. It was found to metabolize mandelic acid by a new pathway involving 4-hydroxymandelic acid, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, and 3,4-dihydroxybenzoic acid as aromatic intermediates. All the enzymes of the pathway were demonstrated in cell-free extracts. L-Mandelate-4-hydroxylase, a soluble enzyme, requires tetrahydropteridine, nicotinamide adenine dinucleotide phosphate, reduced form, and Fe2+ for its activity. The next enzyme, L-4-hydroxymandelate oxidase (decarboxylating), a particulate enzyme, requires flavine adenine dinucleotide and Mn2+ for its activity. A nicotinamide adenine dinucleotide-dependent, as well as a nicotinamide adenine dinucleotide phosphate-dependent, benzaldehyde dehydrogenase has been resolved and partially purified.

Carboxy-Lyases↗
PubMed1992

Discrimination in resolving systems: ephedrine-mandelic acid.

Resolution of mandelic acid with (-)-(1R,2S)-ephedrine in water and ethanol produces intermediate diastereomeric salts with greatly disparate solubilities and melting points. Single crystal X-ray analysis of the less (L) and more (M) soluble (-)-ephedrinium mandelates (I, II) shows crystal structures which are isosteric, each crystallizing in the monoclinic system, space group C2. Protonated ephedrines occupy the same relative positions in the L- and M-salts, and mandelates are in the same general locations. Hydrogen bonds link alternating protonated ephedrine nitrogens and mandelate carboxylate oxygens in each salt forming columns of ions. The helical H-bonded chain winds down the crystallographic 2-fold screw axis. Additional H-bonds form between 2-fold related mandelates in the L-salt. Mixed crystals, containing both mandelate isomers, (2R)- and (2S)-mandelates, are obtained from the resolving system partly depleted of the L-salt. A specimen with nearly equal amounts of the mandelates (III) is also isosteric with the commensurate structures. I (294K), L-salt: a = 18.160(7), b = 6.538(2), c = 13.898(4) A, beta = 92.02(3) degrees, V = 1649.1(9) A3; IIa (294K), M-salt: a = 17.978(11), b = 7.164(4), c = 13.574(6)A, beta = 96.41(4) degrees, V = 1737.3(16) A3; IIb (223K), M-salt: a = 17.805(8), b = 7.115(2), c = 13.50(5) A, beta = 96.89(3) degrees, V = 1697.9(15) A3; III (294K), mixed-salt: a = 18.184(22), b = 6.792(7), c = 13.808(19) A, beta = 93.74(10) degrees, V = 1701.7(35) A3.

Ephedrine↗
PubMed1989

The metabolism of ethylbenzene and styrene to mandelic acid: stereochemical considerations.

1. The stereochemistry of mandelic acid, produced as a major urinary metabolite of ethylbenzene and styrene in rat and man has been investigated. Although these solvents are both achiral they are metabolized to chiral metabolites, via a series of chiral intermediates. 2. Analytical methods (g.l.c.-mass spectrometry, h.p.l.c. and 19F-n.m.r.) have been developed for the determination of the enantiomeric composition of mandelic acid in urine. 3. These methods have been applied to the study of the metabolic stereochemistry of ethylbenzene and styrene in rats dosed orally (100 mg/kg body weight) and in human volunteers exposed to atmospheres containing these solvents at the upper limits prescribed for workplaces by the UK Health and Safety Executive (100 ppm in air). 4. Results show that whereas only the R-enantiomer of mandelic acid was excreted after ethylbenzene exposure, the mandelic acid formed from styrene was essentially racemic. In three workers occupationally exposed to styrene, ratios of R to S isomers of 1.16, 1.27 and 1.14 were found. A synthetic R/S mixture of mandelic acid had an R/S ratio of 1.03. 5. The implications of these findings for the biological monitoring of workers occupationally exposed to stryrene and/or ethylbenzene are discussed.

Animals↗
PubMed1990

The stereoselectivity of 1,2-phenylethanediol and mandelic acid metabolism and disposition in the rat.

1. The steps involved in determining the chirality of the mandelic acid excreted by rats after administration of ethylbenzene and styrene were investigated by studying the fate of racemic, (R)- and (s)1,2-phenylethanediol, a precursor of mandelic acid. These investigations indicate the occurrence of two alternative routes of metabolism for 1,2-phenylethanediol, one involving retention of configuration and the other resulting in the loss of the chiral centre. 2. The stereoselectivity of the disposition of mandelic acid was investigated; rats were dosed with mandelic acid either as the racemate or as the individual enantiomers, G.1.c.-mass spectrometry and h.p.l.c. were used to determine the enantiomers of mandelic acid. 3. There were at least two routes by which mandelic acid could be metabolized and/or excreted; there is a stereoselective pathway in rat for (s)-mandelic acid, which gives rise to phenylglyoxylic acid. 4. The chiral inversion of (s)-mandelic acid to (R)-mandelic acid is reported; although this has been observed in bacteria it has not previously been observed in mammals. 5. The extent to which mandelic acid is metabolized to phenylglyoxylic acid is dependent on the enantiomeric composition of the mandelic acid administered. There is no evidence to indicate significant ketone-alcohol conversion, that is phenylglyoxylic acid is not significantly reduced to mandelic acid in vivo.

Animals↗
PubMed1991

Production of R-(-)-mandelic acid from mandelonitrile by Alcaligenes faecalis ATCC 8750.

R-(-)-Mandelic acid was produced from racemic mandelonitrile by Alcaligenes faecalis ATCC 8750. Ammonium acetate or L-glutamic acid as the carbon source and n-butyronitrile as the inducer in the culture medium were effective for bacterial growth and the induction of R-(-)-mandelic acid-producing activity. The R-(-)-mandelic acid formed from mandelonitrile by resting cells was present in a 100% enantiomeric excess. A. faecalis ATCC 8750 has an R-enantioselective nitrilase for mandelonitrile and an amidase for mandelamide. As R-(-)-mandelic acid was produced from racemic mandelonitrile in a yield of 91%, whereas no S-mandelonitrile was left, the S-mandelonitrile remaining in the reaction is spontaneously racemized because of the chemical equilibrium and is used as the substrate. Consequently, almost all the mandelonitrile is consumed and converted to R-(-)-mandelic acid. R-(-)-Mandelic acid was also produced when benzaldehyde plus HCN was used as the substrate.

Acetonitriles↗
PubMed1976

Urinary mandelic acid concentration after occupational exposure to styrene and its use as a biological exposure test.

Excretion of mandelic acid from workers in the reinforced polyester plastic industry was studied with the determination of urinary mandelic acid concentrations. The styrene exposure level at the workplaces was evaluated with measurements of the styrene concentration in the ambient air. Three different groups (I, II and III) were studied. In group I [n=9, median of the time-weighted average (TWA) of exposure = 23 ppmof styrene, postexposure observation period = 64 h] two excretion slopes were observed, the first with a median half-time of 9.4 h (postexposure period 0--18 h) and a second with a median half-time of 16.6 h (postexposure period 19--64 h). For group II (n=9, median TWA exposure = 248 ppm, postexposure observation period = 15 h) a half-time of 6.4 h was found. These results suggest that the excretion rate of mandelic acid is dependent on the styrene exposure level. In addition the mandelic acid concentrations of 29 workers (group III) before and after the work shift were analyzed. The urinary mandelic acid concentrations of groups I, II and III, sampled immediately after the 8-h work shift, correlated with the 8-h TWA of styrene exposure (n=47, r=0.93). Accordingly about 2,300 mg of mandelic acid per gram of creatinine corresponded to 100 ppm of styrene.

Air Pollutants, Occupational↗