Dietary sesame (Sesamum indicum cultivar Linn) oil inhibits iron-induced oxidative stress in rats

Abstract

The high stability of sesame oil against oxidative deterioration is attributed to lignans in its non-glycerol fraction. The present study evaluates the effects of feeding sesame lignans (sesamin and sesamolin) on Fe2+-induced oxidative stress in rats. Three groups, each of sixteen male weanling WNIN rats, were fed diets containing 200 g casein/kg and 100 g oil/kg (group 1, groundnut oil; group 2, sesame oil; group 3, sesame oil+sesamin (0·4 g/kg). After 45 d of feeding, eight rats from each group were injected with saline (9 g Na Cl/l, controls) intraperitoneally while the remaining eight rats were injected with 30 mg Fe2+/kg body weight as ferrous sulfate in normal saline. The animals were killed after 90 min to evaluate hepatic function and antioxidant status. Compared with those fed groundnut oil (group 1), sesame oil-fed rats (groups 2 and 3) had lower levels of hepatic thiobarbituric acid-reactive substances, serum glutamate:oxaloacetate transaminase activities and serum glutamate pyruvate transaminase activities, indicating protection against Fe-induced oxidative stress. Despite similar tocopherol levels in the three diets, hepatic α-tocopherol levels were higher in rats fed the sesame-oil diets (groups 2 and 3) compared with controls (group 1). However, activities of hepatic antioxidant enzymes (superoxide dismutase and glutathione peroxidase) were significantly (P<0·05) increased only in rats fed higher levels of lignans (group 3). These observations suggest that sesame lignans may have sparing effects on tocopherols. The increased bioavailability of tocopherols in the presence of dietary lignans might be due to the regeneration of oxidized tocopherols. The synergistic effects of lignans with tocols has nutritional and therapeutic implications.