3, 4-Dihydroxymandelic acid

The effect of released norepinephrine wanes quickly, because approx. 90% is actively transported back into the axoplasm, then into storage vesicles (neuronal re-uptake). Small portions of norepinephrine are inactivated by the enzyme catechol-0-methyltransferase (COMT, present in the cytoplasm of postjunctional cells, to yield normeta-nephrine), and monoamine oxidase (MAO, present in mitochondria of nerve cells and postjunctional cells, to yield 3,4-dihydroxymandelic acid). 

From Catechol. Several routes have recently been developed for the synthesis of heliotropin from catechol. In one such route, catechol is converted into 3,4-dihydroxymandelic acid with glyoxylic acid in an alkaline medium in the presence of aluminum oxide. 3,4-Dihydroxymandelic acid is oxidized to the corresponding keto acid (e.g. with copper-(II) oxide), which is decarboxylated to 3,4-dihydroxybenzaldehyde [176]. The latter product is converted into heliotropin, for example, by reaction with methylene chloride in the presence of quaternary ammonium salts [177]. 

The assay procedure for catecholamines based on the formation of fluorescent products with ethylenediamine, originally described by Weil-Malherbe and Bone, 197, 198, 270 and considered by some workers to be the most sensitive method, suffers to some extent by a lack of specificity since catechol and 3,4-dihydroxymandelic acid give the same fluorophore as noradrenaline. However, most of the interfering compounds can be eliminated by use of suitable extraction procedures. 

Deeble DJ, von Sonntag C (1992) Decarboxylation of 3,4-dihydroxymandelic acid induced by the superoxide radical anion a chain reaction. Int J Radiat Biol 62 105 Deeble DJ, Parsons BJ, Phillips GO (1987) Evidence for the addition of the superoxide anion to the anti- oxidant -propyl gallate in aqueous solution. Free Rad Res Commun 2 351-358 Deeble DJ, Parsons BJ, Phillips GO, Schuchmann H-P, von Sonntag C (1988) Superoxide radical reactions in aqueous solutions of pyrogallol and n-propyl gallate the involvement of phenoxyl radicals. A pulse radiolysis study. Int J Radiat Biol 54 179-193 Denisov ET, Denisova TG (1993) The polar effect in the reaction of alkoxy and peroxy radicals with alcohols. Kinet Catal 34 738-744... 

After reuptake of it NE is stored again or it is degraded. The major metabolic pathway of NE is its oxidation into 3,4-dihydroxymandelic acid by the type A of the enzyme monoamine oxidize (MAO). Numerous drugs have MAO as their primary target. Their can be divided into two groups non-reversible MAO inhibitors (MAOIs) and reversible MAO inhibitors (RIMAs). Respective examples for these groups are phenelzine and moclobemide (Blier and de Montigny 1985 Blier et al., 1986). 

Solutes 1 = homo-vanillic acid, 2 = 5-hydroxyindol-3-acetic acid, 3 = 3,4-dihydroxyphenylacetic acid, 4 = tyrosine, 5 - L-DOPA, 6 = dopamine, 7 = octopamine, 8 = adrenaline, 9 = 3,4-dihydroxymandelic acid, 10 = noradrenaline. 

At adrenergic nerve terminals norepinephrine and epinephrine can be taken up, oxidized [via MAO] to 3,4-dihydroxymandelic aldehyde and thence oxidized to 3,4-dihydroxymandelic acid (DOMA) and 3,4-dihydroxyphenylglycol (DHPG). Extracellular DOMA and DHPG can then be converted via COMT to the methylated derivatives VMA and MHPG. 

Li et al. (1990) developed an assay to measure the diphenol oxidase activity of tyrosine by following the conversion of 3,4-dihydroxymandelic acid (DHMA) to 3,4-dihydroxybenzaldehyde (DHBZ). Tyrosinase is involved in the formation of melanotic pigments in a wide variety of plants and animals. 

Separation of 3,4-dihydroxymandelic acid and 3,4-dihydroxybenzaldehyde occurred at 40°C on an Altex Ultrasphere ODS column (4.6 mm x 250 mm, 5 fim). The mobile phase at a flow rate of 1.0 mL/min consisted of 0.4 citrate buffer (pH 3.2) containing 0.5 mM Na2EDTA and 5% (v/v) acetonitrile. An amperometric detector fitted with a glassy carbon electrode was used. The electrode was maintained at +650 mV. 

Deamination to the deaminated acid metabolite, 3,4-dihydroxymandelic acid (DHMA), is not a favored pathway. 

Fig. 4.4.12. Separation of a mixture of acidic and basic catecholamines on a LiChrosorb RP-8 column (0.28x25 cm). Eluent Water containing 0.02 M citrate (pH 2.5)/l% propanol/NaCIQ4 (0.08 M)/0.3% sodium dodecyl sulphate. Peaks DHMA, 3,4-dihydroxymandelic acid VMA, vanilmandelic acid HGA, 2,5-dihydroxyphenylacetic acid DOPAC, 3,4-dihydroxyphenylacetic acid 5-HIAA, 5-hydroxyindole-3-acetic acid HVA, homovanillylmandelic acid E, epinephrine NE, norepinephrine N-Syn, norsyneph-rine Syn, synephrine Dopa, 3,4-dihydroxyphenylalanine NM, normetanephrine MN, metanephrine Isopren, isoprenaline 3-H-Tyrm, dopamine Tyrm, tyramine 3-M-Tyrm, 3-methoxytyramine. Reprinted from Ref. 21 with permission.

Ribotta et al. [281] studied a series of six catecholamine metabolites (vanilman-delic acid, homovanillic acid, 3,4-dihydroxymandelic acid, 3,4-dihydroxy- and 4-hydroxy-3-methoxyphenylacetic acid, vanillic acid). They were well resolved on a C g column (electrochemical detector, 0.75 V). A 15/85 methanol/water (2mM tetrabutylammonium bromide at pH 4.5) mobile phase eluted all compounds in <10 min. A linear range of 3 x 10 to 5 x 10 M and detection limits of 2 x 10 (S/N = 3) were reported. A considerable amount of supportive data such as retention time vs. pH, % methanol, and tetrabutylammonium bromide concentration is also given. Also, detector response versus potential from 0.3 to 0.8 V is shown. 

Analysis of Urinary Homovanillic Acid, Vanilmandelic Acid and 3,4-Dihydroxymandelic Acid by Mass Fragmento graphy... 

Wada, Y. and Watanabe, N., Urinary excretion of 3,4-dihydroxymandelic acid (doma) in patients with hypertension and with hyperthyroidism, Tohoku J. Exp. Med. 84, 161 (1964). 

Ala-ala and related compounds D,L-4-hydroxy-3-metho-xymandelic acid D,L-3,4-dihydroxymandelic acid... 

As illustrated in Figure 4.10, noradrenaline (norepinephrine) may be )V-methylated in some human tissues. Deamination of either noradrenaline or adrenaline (epinephrine) leads to 3,4-dihydroxymandelic aldehyde, and this intermediate may be oxidised to 3,4-dihydroxymandelic acid (DHMA)... 

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