RESUMO
The redox potentials have been determined for nine azaanthraquinones in phosphate buffer at pH 7.2 by means of cyclic voltammetry. A definite correlation has been found between the redox potentials and the inhibitory effects of the azaanthraquinones on Epstein-Barr virus early antigen (EBV-EA) activation. It has further been shown that the correlation can be made better by introducing an electronic property, i.e., the atomic charge at O11 as an additional parameter.
Assuntos
Antraquinonas/química , Antivirais/farmacologia , Compostos Aza/química , Herpesvirus Humano 4/efeitos dos fármacos , Ativação Viral/efeitos dos fármacos , Células Cultivadas , Eletroquímica , Concentração de Íons de Hidrogênio , Indicadores e Reagentes , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Oxirredução , Espectrofotometria InfravermelhoRESUMO
Reaction mechanisms of polyphenolic antioxidants were studied using electrochemical methods (flow column electrolysis and cyclic voltammetry). In flow column electrolysis, the numbers (ns) of electrons involved in the oxidation of catechols (chlorogenic acid and caffeic acid) became larger than two (i.e. the number of -OH moieties) at pH > 7; the n-values finally reached ca. 4 at pH 10. Other polyphenols including catechin, ellagic acid, and curcumin exhibited higher n-values than the numbers of -OH moieties in the whole pH range studied (4 < pH < 10). Such unusually large n-values for polyphenols were found to correlate to their irreversible behavior in cyclic voltammetry. A digital simulation analysis of the voltammograms of chlorogenic acid clearly showed that the electrode reaction at higher pHs can be elucidated in terms of a quasi-reversible electron transfer followed by a chemical reaction and also suggested that the chemical reaction is of second order to the concentration of chlorogenic acid, i.e. a dimerization reaction. In a similar manner, polyphenolic antioxidants generally undergo certain chemical reactions on the occasion of their oxidation. As a result, some oxidizable, phenolic -OH moieties are reproduced in the polymeric products. The unusually large n-values of polyphenols and thus their higher radical scavenging activities may be ascribed to such reproduction of -OH moieties by oxidative polymerization.
Assuntos
Antioxidantes/química , Ácido Clorogênico/química , Catequina/química , Curcumina/química , Eletrodos , Eletrólise , Elétrons , Ácido Elágico/química , Concentração de Íons de Hidrogênio , Modelos Químicos , Oxirredução , PolímerosRESUMO
The redox potentials have been determined for nine anthraquinones in phosphate buffer at pH 7.2 by means of cyclic voltammetry. A definite correlation has been found between the redox potentials and the inhibitory effects of the anthraquinones on the EBV-EA activation. It has further been shown that the correlation can be made better by introducing an electronic property, i.e. the atomic charge at O12 as an additional parameter.
Assuntos
Antraquinonas/química , Antraquinonas/farmacologia , Anticarcinógenos/farmacologia , Herpesvirus Humano 4/efeitos dos fármacos , Herpesvirus Humano 4/crescimento & desenvolvimento , Ativação Viral/efeitos dos fármacos , Antígenos Virais/fisiologia , Carcinógenos/farmacologia , Eletroquímica , Humanos , Concentração de Íons de Hidrogênio , Linfócitos/efeitos dos fármacos , Linfócitos/virologia , Oxirredução , Oxigênio/química , Acetato de Tetradecanoilforbol/antagonistas & inibidores , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
A simple voltammetric method for the determination of phosphonate ion is described. A 12-molybdodiphosphonate complex is formed in a 50mM Mo(VI)-0.5M HCl-70% (v/v) CH(3)CN system containing phosphonate ion. The yellow heteropolyanion undergoes apparent two-step reductions at a glassy carbon electrode. The voltammetric reduction currents depend linearly on the phosphonate concentration in the range 1 x 10(-5)-1 x 10(-3)M.
