Background: It has been reported that induction of diabetes mellitus is associated with increasing production of reactive oxygen species and depletion of the antioxidants defense systems. Grape seed has potent-free radical scavengers called proanthocyanidins and hence provide significant protection against oxidative stress. The purpose of this study was to determine whether black grape seed (Shahani grape) plays any protective role against hyperglycemia and beta cells damages in the injected alloxan rats.

Materials and Methods: Adult male Wistar rats (200–220g) were purchased from the institute pastor animal house in Iran. Totally, 90 rats were used and divided into three groups: 1) control group (given 2 ml distilled water) 2) a test group given high dosage grape seed (2gr/kg.bw/day) group 3) another test group given low dosage grape seed (1gr/kg.bw/day). Rats in groups 2 and 3 were pretreated by aqueous grape seed’s suspension via oral gavage). Pretreatment continued for 4 days (once daily). Then alloxan was injected subcutaneously (70 mg/w). 24, 48 and 72 hours after alloxan injection, the animals were sacrificed by decapitation. Their blood was collected and its serum glucose level (by commercially kit)¸ serum insulin level (by ELISA kit) and serum total antioxidant power (by FRAP assay) were measured.

Results: The results indicated that only high dosage�of grape seeds significantly inhibited the increase of serum glucose level caused by alloxan (p<0.05). Also, high and low dosages grape seed caused a significant increase in serum insulin level on pretreated rats in 24, 48 and 72 hours after alloxan injection (p<0.05). While serum total antioxidant levels increased significantly (24 and 48 hours) in rats receiving low doses grape seed (p<0.05) it was not significant in other groups.

Conclusion: The study suggests that grape seed is effective in ameliorating the oxidative damage to pancreatic tissues in experimental diabetes mellitus. Such an effect may be related to their potent antioxidant properties among other factors. It seems that in addition to the existing proanthocyanidin factor in the grape seed, there also exist other related factors.