Phenolic
acids are widespread in plant foods; they contain important
biological and pharmacological properties, some of which were shown to be effective in preventing
cancer. We investigated the modulatory effects of phenolic
acids on an
antioxidant system in male Sprague-Dawley rats. Rats were orally administrated
gentisic acid (GEA),
gallic acid (GA),
ferulic acid (FA), and
p-coumaric acid (p-CA) at a dosage of 100 mg/kg
body weight for 14 consecutive days. At this dose, the activities of hepatic
superoxide dismutase (SOD),
glutathione peroxidase (GPx), and
catalase were greater after administration of all 4 phenolic
acids compared with the control group (P < 0.05). The activities of these
enzymes in the small intestine of rats were also significantly greater after GA and p-CA treatment compared with controls. The changes in hepatic CuZnSOD, GPx, and
catalase mRNA levels induced by phenolic
acids were similar to those noted in the
enzyme activities.
Oxidized glutathione levels were lower (P < 0.05) in the liver of all
phenolic acid-supplemented rats, whereas
reduced glutathione was markedly higher than in control rats, especially after administration of GA and p-CA. The liver homogenates obtained from rats that had been administered phenolic
acids had higher
oxygen radical absorbance capacity than those obtained from control rats. Immunoblot analysis revealed an increased total level of Nrf2, a
transcription factor governing the antioxidant response element in
phenolic acid-supplemented rats.
Phenolic acid-mediated
antioxidant enzyme expression was accompanied by upregulation of
multidrug resistance-associated protein Mrp3. These experiments show that modulation of phase II
antioxidant enzymes and oxidative status in the liver by phenolic
acids may play an important role in the protection against adverse effects related to mutagenesis and oxidative damage.