4-Mercaptoimidazoles derived from the naturally occurring antioxidant ovothiols 1. Antioxidant properties.
4-Mercaptoimidazoles derived from the naturally occurring family of antioxidants, the ovothiols, were assayed for their antioxidant properties. These compounds are powerful HOCl scavengers, more potent than the aliphatic thiol N-acetylcysteine. They react slowly with hydrogen peroxide with second order rate constants of 0.13-0.89 M(-1)s(-1). Scavenging of hydroxyl radical occurs at a diffusion-controlled rate (k=2.0-5.0 x 10(10)M(-1)s(-1)) for the most active compounds, which are also able to inhibit copper-induced LDL peroxidation. The combination of radical scavenging and copper chelating properties may explain the inhibitory effects on LDL peroxidation. Two molecules of mercaptoimidazole can chelate a copper ion and form a square planar complex detected by EPR. Compounds bearing an electron-withdrawing group on position 2 of the imidazole ring are the most potent antioxidant molecules in this series.
Zoete
V
V
Laboratoire de Chimie Organique Physique associée à l'Ecole Nationale Supérieure de Chimie de Lille, ESA CNRS 8009, Villeneuve d'Ascq, France.
Bailly
F
F
Vezin
H
H
Teissier
E
E
Duriez
P
P
Fruchart
J C
JC
Catteau
J P
JP
Bernier
J L
JL
D000975:Antioxidants / Q000494:pharmacology*; D002614:Chelating Agents; D003300:Copper / Q000737:chemistry / Q000494:pharmacology; D016166:Free Radical Scavengers; D006861:Hydrogen Peroxide / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D006997:Hypochlorous Acid / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry* / Q000494:pharmacology*; D015227:Lipid Peroxidation; D008077:Lipoproteins, LDL / Q000737:chemistry; D008762:Methylhistidines / Q000737:chemistry*; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000737:chemistry*
D000975:Antioxidants; D002614:Chelating Agents; D016166:Free Radical Scavengers; D007093:Imidazoles; D008077:Lipoproteins, LDL; D008762:Methylhistidines; D013438:Sulfhydryl Compounds; C061475:ovothiol A; D017665:Hydroxyl Radical; D006997:Hypochlorous Acid; D003300:Copper; D006861:Hydrogen Peroxide