Curcumin protects against gallic acid-induced oxidative stress, suppression of glutathione antioxidant defenses, hepatic and renal damage in rats.

Curcumin (Cur) and gallic acid (Gal) are major food additives. Cur has well-known antioxidant properties, whereas Gal has both antioxidant and pro-oxidant effects. The present study investigated the effects of oral administration of Gal with or without Cur on antioxidant enzymes activities, glutathione (GSH) and the enzymes in its metabolism in rat liver in vivo and markers of tissue damage in the serum. Results showed that the increase in serum creatinine level, alkaline phosphatase and lactate dehydrogenase activities by Gal treatment were inhibited by combined administration of Gal and Cur. The decrease in GSH-peroxidase, GSH-S-transferase, superoxide dismutase and GSH-reductase activities by Gal treatment were inhibited when both Gal and Cur were administered together. The malondialdehyde concentration and catalase activity were significantly increased following administration of Gal but not when the administration of Gal was combined with Cur. Finally, the increase in GSH level was seen following administration of Cur alone or in combination with Gal but not with Gal alone. These results suggest that Gal might induce oxidative stress in the rat liver and affect renal function that can be inhibited by the combined administration of Gal and Cur.