Investigating the effects of emulsion formulations of olive leaf (olea europaea l.) ethanol extract and oleuropein isolated from the extract in diabetic rats

Aim: This study was designed to investigate the effects of emulsion formulations of olive leaf (Olea europaea L.) ethanol extract and oleuropein isolated from the extract in streptozotocin (STZ)-induced diabetic rats. Material and Method: Diabetic rats were treated with oral administrations of the emulsion formulations of the olive leaf ethanol extract (330 and 500 mg/kg b.w.) and oleuropein (150 and 225 mg/kg b.w.) in liquid form daily at a single dose for 4 weeks. At the end of the experimental period, the liver tissue samples of rats were also taken to determine of SOD activities, GSH and MDA levels. Also, the blood samples of rats were taken to determine of AST, ALT and glucose levels. Results: After the oral administrations of oleuropein or the emulsion containing oleuropein, at two different doses, a statistically significant increase in SOD activities and GSH levels and a statistically significant decrease in MDA levels of the treated diabetic rats were observed (p<0.05). Also, a statistically significant decrease in their AST and ALT levels were observed (p<0.05). The oral administration of the emulsion containing oleuropein at the high dose was found to be more effective than that of the low dose (p<0.05). In addition, a significant decrease in glucose levels of the diabetic rats receiving oleuropein at high dose or the emulsion containing oleuropein at high dose was observed (p<0.05). After the oral administration of the emulsion containing the extract at the high dose, a significant increase in GSH levels (p<0.05) and SOD activities (p<0.05) and a significant decrease in MDA levels (p<0.05) of the treated diabetic rats were observed. Also, the oral administration of the emulsion containing the extract at the high dose significantly decreased AST and ALT levels of the treated diabetic rats, but the decreases are not close to normal levels. Conclusion: The results indicate that the antidiabetic effect of the emulsion formulation of olive leaf ethanol extract may be due to its antioxidant activity, and the antidiabetic effect of the emulsion formulation of oleuropein isolated from the extract may be due to its hypoglycemia effect and antioxidant activity restraining the oxidative stress which is widely associated with diabetes.