Background: Diabetes mellitus is a major endocrine disorder and growing health problem in most countries. Diabetes manifested by experimental animal models exhibit high oxidative stress due to persistent and chronic hyperglycemia which increases the generation of free radicals, Streptozotocin (STZ) provides an animal model of type 1 diabetes. Thereby depleting the activities of antioxidative defense systems with alteration of antioxidant activities of enzymes such as green tea and curcumin. Aim: Biochemical histological and histochemical investigations were carried on to reveal the effect of STZ on the liver and pancreas cells. Natural antioxidants were used as a new way for ameliorated diabetic effect on the cells. Material and methods: Diabetes was induced by a single intraperitoneal injection of freshly prepared STZ dissolved in 0.05 M of sodium citrate buffer, pH=4.6, (STZ; 45 mg/kg B.wt.).Three days after degeneration of beta cells, diabetes was induced in all animals. After induction of diabetes, diabetic and normal animals were kept in metabolic cages separately. Green tea (EGCG) and curcumin are used as a natural antioxidant to improve the disorders and structural changes induced by STZ. Cellular and histochemical investigations were carried on the changes induced in pancreatic and hepatic tissues. Body weight, levels of serum glucose and insulin were calculated, and compared. For a microscopic study of degeneration of both hepatocytes and pancreatic cells of diabetic rats, tissue samples from diabetic and treated rats were collected, and pathologically examined. Results: Our investigations reveled that there was a detectable amelioration on the injures induced by STZ on both hepatocytes and pancreatic cells using green tea or curcumin with a detectable dose level. Also it can be observed that the ameliorated effect induced was a time dependant. Conformation of these results from histochemical detection of glycogen and DNA contents were detected by PAS and feulgen reactions. Conclusion: Curcumin and green tea looks to have a powerful effect against diabetic cell injury induced in both rat liver and pancreas. The ameliorating effect seems to be time dependant.