The potential hypoglycemic effect of aqueous extract of gamma-irradiated olive leaves in alloxan-induced diabetic rats

Background: The present study aimed to evaluate the effect of gamma-irradiation (5kGy) on total phenolic and total flavonoid content, antioxidant capacity, and concentration of phenolic compounds of olive leaves, and to assess the potential hypoglycemic effect of gamma-irradiated olive leaf extract (GOLE) in alloxan-induced diabetic rats. Results: The results indicated that gamma-irradiation caused a significant increase in the total phenol content, total flavonoids, and antioxidant activity in olive leaves compared to raw leaves. High-Performance Liquid Chromatography (HPLC) analysis showed that gamma-irradiation increased the values of phenolic compounds in olive leaves such as hydroxytyrosol, hydroxytyrosol-1-glucoside, rutinhydrate, and tyrosol. The results of the biological study showed that the co-administration of alloxan (150 mg/kg body weight) together with either raw (ROLE) or gamma-irradiated olive leaf extract (GOLE) (1ml/100 gm /body weight/ day/ 8 weeks) to rats caused hypoglycemia, hyperinsulinemia, decreased level of the homeostatic index of insulin resistance (HOMA-IR), alpha-amylase and alpha-glucosidase activity, and a significant elevation in hepatic glycogen storage and the activity of hepatic hexokinase, glucose-6phosphate dehydrogenase, pyruvate kinase and glycogen synthase associated with a significant reduction in hepatic glucose 6-phosphatase, fructose 1,6-bisphosphatase, glycogen phosphorylase, the activity of liver marker enzymes and decreased level of serum creatinine, uric acid, and urea compared to the diabetic group. Conclusion: The results also showed that the anti-diabetic effect of GOLE was more significant than that observed with ROLE because of the effectiveness of gamma-irradiation (5 kGy) in improving the antioxidant activity and increasing the concentration of biological components of olive Leaf.