6- hydroxyindole-3-acetic acid

FIGURE 3-27 Three-dimensional chromatogram for oxidizable biological compounds at a multichannel amperometric detection system, consisting of an array of 16 carbon-paste electrodes held at different potentials. AA = ascorbic acid NE = norepinephrine DOPAC = 3,4-dihydroxyphenylacetic acid 5-HIAA = 5-hydroxyindole-3-acetic acid DA = dopamine HVA = homovanillic acid. (Reproduced with permission from reference 68.)... 

Figure 2 Selective electrochemical detection of a mixture on multielectrode amper-ometry. AA = Ascorbic acid, NE = norepinephrine, DOPAC = 3-4-dihydroxy-phenylacetic acid, E = epinephrine bitartrate, 5-HIAA = 5-hydroxyindole-3-acetic acid, HVA = homovanillic acid, TRP = tryptophan, 5-HT = 5-hydroxytryptamine, and 3-MT = 3-methoxytyramine (separated by RPLC). Detection was with a 4-electrode glassy carbon array, with electrode 1 at 500 m V) electrode 2 at 700 mV, electrode 3 at 900 mV, and electrode 4 at 1100 mV. Note that at electrode 1, HVA, TRP, and 3-MT are not seen. At electrode 2, only TRP is not seen. A standard calomel electrode was used as reference. (Reprinted with permission from Hoogvliet, J. C., Reijn, J. M., and van Bennekom, W. P., Anal. Chem., 63, 2418, 1991. 1991 Analytical Chemistry.)...

Figure 9 Chromatogram of 5-hydroxyindoles derivatized with 6-AMP. Peaks (2.5 pmol each on column) 1 = 5-hydroxytryptophan 2 = serotonin 3 = 5-hydroxyindole-3-acetic acid. (From Ref. 50.)...

Metabolites of biogeiuc amines have also been analyzed by GC-ECD. For the simultaneous analysis of 5-hydroxyindole-3-acetic acid (5-HIAA), homovanillic acid (HVA) and m- and p-hydroxyphenylacetic acid (m-, p-HPAA), (metabolites of 5-HT, DA, and m- and p-tyramine acid respectively) in urine, a simple acidic extraction followed by derivatization with PFPA (derivatizes phenols) and hexafluoroisopropanol (deriva-tizes carboxylic acid groups) has been used (Davis et al., 1982 Baker et al., 1987). 

Baker GB, Yeragani VK, Dewhurst WG, Coutts RT, Mac Donald RN, et al. 1987. Simultaneous analysis of urinary m- and p-hydroxyphenylacetic add, homovanillic acid and 5-hydroxyindole-3-acetic acid using electron-capture gas chromatography. Biochem Arch 3 257. 

Numerous assays are also available in the literature for analysis of biogenic amines and their acid metabolites in brain tissue. For example, Chi and colleagues (1999) developed a rapid and sensitive assay for analyzing NE, DA, 5-HT, 5-hydroxyindole-3-acetic acid (5-HIAA), and homovanilHc acid (HVA) in rat brain. The assay used a C18 column (150 x 4.6 mm) coupled to an amperometric electrochemical detector. The mobile phase consisted of a phosphate buffer (pH 4.75) and octane sulphonic acid as an ion-pair reagent in acetonitrile. The sensitivity of the analytes reported was 3-8 pg on column. 

Kroll CA, Magera MJ, Helgeson JK, Matern D, Rinaldo P (2002) A liquid chromatography-tandem mass spectrometry method for the determination of 5-hydroxyindole-3-acetic acid in urine. Clin Chem 48 2049-2051... 

Baker GB, Reynolds GP (1989) Biogenic amines and their metabolites in Alzheimer s disease noradrenaline, 5-hydroxytryptamine and 5-hydroxyindole-3-acetic acid depleted in hippocampus but not in substantia innominata. Neurosci. Lett. 100 335-339. 

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. 

C10H9NO3 5-hydroxyindole-3-acetic acid 54-16-0 27.50 1.2860 2 19119 C10H10O2 methyl cinnamate 1754-62-7 36.00 1.0420 1... 

Chou PP, Jaynes PK. Determination of urinary 5-hydroxyindole-3-acetic acid using solid-phase extraction and reversed-phase high-performance liquid chromatography with electrochemical detection. J Chromatogr 1985 341 167-71. 

Skrinska V, Hahn S. High-performance Hquid chromatography of 5-hydroxyindole-3-acetic acid in urine with direct sample injection. J Chromatogr 1984 311 380-4. 

Stroomer AE, Overmars H, Abeling NG, van Gennip AH. Simultaneous determination of acidic 3,4-dihydroxyphenylalanine metabolites and 5-hydroxyindole-3-acetic acid in urine by high-performance hquid chromatography. Clin Chem 1990 36 1834-7. 

Fig. 17. GLC of a mixture of indole derivatives (1 /jg of each derivative injected). For conditions see text. IAN = indole-3-acetonitrile lAA-ME = methyl ester of in-dole-3-acetic acid lAA-EE = ethylindole 3-acetate ICA-ME = methyl ester of in-dole-3-carboxylio acid IPA-ME = methyl ester of indole-3-propionic acid IBA-ME = methyl ester of indole-3-butyrio acid 6-OH-IAA-ME = 5-hydroxyindole-3-acetic acid (methyl ester). Reproduced from Brook et al. (B22) with permission.

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.

Norepinephrine reduction can be due to a severe cell loss in LC of AD brains. Serotonin, its metabolite 5-hydroxyindole-3-acetic acid and norepinephrine are measured to be decreased in hippocampal formation. The substantia innominata may be unaffected (Baker and Reynolds, 1989). The loss of serotonin correlates to many neuropathological findings in serotonergic cells of the nuclei raphe (Quirion et al., 1986). 

Serotonin, or 5-HT, is biosynthesized (3) from its dietary precursor L-tryptophan (Fig. 14.1). Serotonergic neurons contain tryptophan hydroxylase (L-tryptophan-5-monooxygenase) that converts tryptophan to 5-hydroxytryptophan (5-HTP) in what is the rate-limiting step in 5-HT biosynthesis and aromatic L-amino acid decarboxylase (previously called 5-HTP decarboxylase) that decarboxylates 5-HTP to 5-HT. This latter enzyme also is responsible for the conversion of L-DOPA to dopamine (see Chapter 12). The major route of metabolism for 5-HT is oxidative deamination by monoamine oxidase (MAO-A) to the unstable 5-hydroxyindole-3-acetaldehyde, which is either reduced to 5-hydroxytryptophol ( 15%) or oxidized to 5-hydroxyindole-3-acetic acid ( -85%). In the pineal gland, 5-HT is acetylated by 5-HT N-acetyltransferase to N-acetylserotonin, which undergoes O-methylation by 5-hydroxyindole-O-methyltransferase to melatonin. 

HIAA, 5-hydroxyindole-3-acetic acid DOPAC, 3,4-dihydroxyphenylacetic add HVA, homovanillic acid AA, ascorbic add and UA, uric acid. 

X 10" M n= ) and 5-hydroxyindole-3-acetic acid (Ka = 2.0x 10" M = 1). The rhenium(I) indole complexes can inhibit another indole-binding protein, tryptophanase. A standard assay, which is on the basis of the conversion of L-serine to pyruvate by the enzyme, has been carried out. Under the standard experimental conditions, at [L-serine] = 800 mM, free indole inhibit 53% of the enzyme activity, while the indole-containing complexes... 

One of its metabolites, 5-hydroxyindole-3-acetic acid, is gaining more and more significance in clinical diagnosis. Increased amounts of it are eliminated in the urine of cancer cases. Nothing is yet known about the function of serotonine in plant metabolism. 

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