Antioxidant and neutrophil-inhibiting properties of new 2-O-methyl-6-(alkylthio)ascorbic acid derivatives.
J Med Chem
; 36(25): 4021-9, 1993 Dec 10.
Article
en En
| MEDLINE
| ID: mdl-8258824
ABSTRACT
A series of new 6-(alkylthio)ascorbic acids was synthesized, and their inhibitory effects on lipid peroxidation and the oxidative burst of human neutrophils were tested. Of 12 structurally different lipophilic ascorbic acid derivatives 6-S-n-hexadecyl-2-O-methyl-6-deoxy-6-thio-L-ascorbic acid (7b; B-003) inhibited the Fe2+/ADP-induced lipid peroxidation of rat liver microsomes with an IC50 value of 2 microM. In human neutrophils, 7b most potently inhibited the fMLP-induced oxidative burst in a cell density-dependent manner with an IC50 value of 0.6 microM at 5 x 10(5) cells/mL. Shorter alkyl chain lengths decreased the inhibitory potency for both lipid peroxidation and oxidative burst, but in general no correlation was found between the two parameters. Likewise, 6-S-n-hexadecyl-3-O-methyl-6-thio-L-ascorbic acid (7c; B-015), the regioisomer of 7b, was a potent antioxidant but did not affect the oxidative burst. Since superoxide anions generated by xanthine/xanthine oxidase were not quenched by 7b, it became evident that its target was somewhere between receptor stimulation and NADPH-oxidase activation. By measuring the cellular concentrations of 7b and 7c, an accumulation of the first was found explaining its potency and the dependence on cell density. Expecting a pKa value of 3.3 for 7b and 7.7 for 7c a protonophore action of 7b was likely and could be verified by the drop in intracellular pH (pHi) which did not occur with 7c. Ionophores such as nigericin, CCCP, or propionic acid also lowered the pHi but did not inhibit the oxidative burst, indicating that the pHi drop was not the cause for this inhibition. 7b also strongly inhibited the fMLP-induced secretion of azurophilic (IC50 = 7 microM) and specific (IC50 = 2.5 microM) granules.
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Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Ácido Ascórbico
/
Peroxidación de Lípido
/
Neutrófilos
/
Antioxidantes
Límite:
Animals
/
Humans
Idioma:
En
Revista:
J Med Chem
Asunto de la revista:
QUIMICA
Año:
1993
Tipo del documento:
Article