42241-03-2Relevant academic research and scientific papers
Electrochemical oxidation of histamine and serotonin at highly boron- doped diamond electrodes
Sarada,Rao, Tata N.,Tryk,Fujishima
, p. 1632 - 1638 (2007/10/03)
The electrochemistry of histamine and serotonin in neutral aqueous media (pH 7.2) was investigated using polycrystalline, boron-doped diamond thin- film electrodes. Cyclic voltammetry, hydrodynamic voltammetry, and flow injection analysis (FIA) with amperometric detection were used to study the oxidation reactions. Comparison experiments were carried out using polished glassy carbon (GC) electrodes. At diamond electrodes, highly reproducible and well-defined cyclic voltammograms were obtained for histamine with a peek potential at 1.40 V vs SCE. The voltammetric signal-to-background ratios obtained at diamond were I order of magnitude higher than those obtained for GC electrodes at and above 100 μM analyte concentrations. A linear dynamic range of 3-4 orders of magnitude and a detection limit of 1 μM were observed in the voltammetric measurements. Well-defined sweep rate-dependent voltammograms were also obtained for 5-hydroxytryptamine (5-HT). The characteristics of the voltammogram indicated lack of adsorption of its oxidation products on the surface. No fouling or deactivation of the electrode was observed within the experimental time of several hours. A detection limit of 0.5 μM (signal-to-noise ratio 13.8) for histamine was obtained by use of the FIA technique with a diamond electrode. A remarkably low detection limit (10 nM) was obtained for 5-HT on diamond by the same method. Diamond electrodes exhibited a linear dynamic range from 10 nM to 100 μM for 5-HT determination and a range of 0.5-100 μM for histamine determination. The FIA response was very reproducible from film to film, and the response variability was below 7% at the actual detection limits.
Influence of L-Cysteine on the Oxidation Chemistry of Serotonin
Wrona, Monika Z.,Singh, Satendra,Dryhurst, Glenn
, p. 421 - 445 (2007/10/02)
L-Cysteine (CySH) intervenes in the normal electrochemically driven oxidation of 5-hydroxytryptamine (5-HT; serotonin) at physiological pH by scavenging the quinone imine proximate oxidation product of this indolic neurotransmitter to give 4-S-cysteinyl-5-hydroxytryptamine (4-S-CyS-5-HT). The latter cysteinyl conjugate is more easily electro-oxidized than 5-HT and, in the presence of free CySH, undergoes a complex series of reactions leading to 8-(2-aminoethyl)-1,2,3,5,6,9-hexahydro-5,9-dioxo-pyrrolobenzothiazine-2-carboxylic acid (20) and N--3-(2-aminoethyl)-1,4-dihydro-4-oxo-5H-indol-5-ylidene>-L-cysteine (4). CySH also reacts with another normal oxidation product of 5-HT, tryptamine-4,5-dione, to give 4 and 20. There is evidence that aberrant oxidative metabolism of 5-HT occurs in the brains of Alzheimer's Disease patients. In the event that such reactions occur in the cytoplasm of serotonergic nerve terminals or axons they would necessarily expose electrophilic intermediates and products to the intraneuronal nucleophiles CySH and GSH. The results of this study indicate that 4 and 20 might represent aberrant oxidative metabolites formed in such reactions. However, the ease of oxidation of 4-S-CyS-5-HT compared to 5-HT suggest that this conjugate is likely to be only a transient species in vivo under conditions where the neurotransmitter is oxidized.
