Antioxidative properties of probucol estimated by the reactivity with superoxide and by electrochemical oxidation

The reaction of probucol with superoxide (O(2)radical anion) was investigated in acetonitrile using both electron spin resonance (ESR) and electrochemical techniques. The formation of phenoxyl radical was observed during the reaction of probucol with O(2)radical anion by ESR spectroscopy. The reaction of probucol with O(2)radical anion in acetonitrile was followed by cyclic voltammetry. With the addition of probucol, the oxidation peak current of O(2)radical anion decreased concentration dependently. This suggests that probucol reacts with O(2)radical anion, that is, probucol scavenges O(2)radical anion in acetonitrile. 2,6-Di-tert-utyl-p-benzoquinone was identified as the major product of the reaction of probucol with O(2)radical anion in acetonitrile. Electrochemical oxidation of probucol was also performed. Probucol gives an irreversible oxidation peak at ca. + 1.4 V vs. the saturated calomel electrode in the cyclic voltammogram. Controlled-potential electrolysis was carried out at + 1.2 V in a divided cell. 2,6-Di-tert-butyl-p-benzoquinone, 4,4'-dithiobis(2,6-di-tert-butylphenol), and 4,4'-trithiobis(2,6-di-tert-butylphenol) were identified as the products of anodic oxidation. These re ox properties of probucol may correlate with the physiological activities.