Effect of antioxidant protection by p-coumaric acid on low-density lipoprotein cholesterol oxidation

Mechanisms in which p-coumaric acid (CA) acts as an antioxidant are not wel l understood. This study investigated whether CA can act as a direct scaven ger of reactive oxygen species (ROS) and whether it minimizes the oxidation of low-density lipoprotein (LDL). Rats were administered CA in drinking wa ter at low or high doses for 10, 21, and 30 days (uptakes were 29 and 317 m g/day, respectively). Blood levels of 8-epiprostaglandin F-2 alpha were mon itored as a marker of LDL oxidation. Oral administration of CA (317 mg/day) for 30 days significantly inhibited LDL oxidation. CA also reduced LDL cho lesterol levels in serum but had no effect on levels of high-density lipopr otein cholesterol. In vitro studies that used electron spin resonance in co mbination with spin trapping techniques were used to determine the ability of CA to scavenge ROS and alter LDL oxidation. CA effectively scavenged . O H in a dose-dependent manner. IC50 and maximum velocity for CA scavenging o f . OH were 4.72 mu M and 1.2 mu M/s, respectively, with a rate constant of 1.8 X 10(11) M-1.s(-1). Our studies suggest that the antioxidant propertie s of CA may involve the direct scavenging of ROS such as . OH.