Abstract
The protective role of antioxidants against free-radical associated diseases has been widely studied, leading to the development of new types of antioxidants to remove reactive oxygen species such as O2•- and •OH. We synthesized a new type of synthetic antioxidant in which the catechol (B ring) and chroman moieties (AC ring) within the (+)-catechin (CA) structure were constrained to be planar. As compared with CA, planar catechin (PCA) showed strong radical scavenging activities towards both galvinoxyl and cumylperoxyl radicals. Reduced prooxidant activity was also observed, consistent with the dianion form of PCA being weaker at generating O2•- than the dianion form of CA. PCA completely inhibited DNA-strand scission induced by the Fenton reaction, whereas CA exhibited not only antioxidant properties but also prooxidant properties consistent with enhanced DNA strand cleavage. As compared with hydrophilic CA, the lipophilicity of PCA due to its planarity may aid in penetration of these antioxidant molecules past the cell membrane. Further development of planar PCA may be a favorable approach towards new clinically useful antioxidants for the treatment of free-radical associated diseases.
