RESUMO
Diabetes mellitus is a chronic metabolic disorder with many complications which has associated with oxidative stress. The present work aimed to study the protective effect of the Egyptian guava [Psidium guajava L.] leaves aqueous extract on streptozotocin [STZ]-induced diabetic rats and its complementary effects. The volatile compounds of guava leaves aqueous extract were isolated and analyzed by using GC and GC/MS. The total phenolic content and in vitro antioxidant activity were done by Folin-Ciocalteu reaction and thiobarbituric acid [TBA] assay, respectively. Four groups of rats [six rats each] used in this study [control, guava extract supplemented, STZ-diabetic, and protected groups]. Serum glucose level was determine as well as liver function, kidney function, lipid profile, activities of some antioxidant enzymes, blood hemoglobin, and histopathological changes in the liver, kidney and pancreas were investigated. Fifty six components were identified using GC and GC/MS. The main chemical compounds in guava leaves volatile oils were; alpha-pinene [11.77%], epi-alpha-bisabolol [10.85%], 1, 8-cineol [9.22%], 1-epi cubenol [8.56%], globulol [5.88%], thujone [5.35%], hexenal [5.03%] and terpipineol [4.35%]. The Egyptian guava volatile extract exhibited a high antioxidant activity in vitro. Also, the results revealed that administration of aqueous guava extract [1gm/dl] to streptozotocin [STZ] induced diabetic rats for 4 weeks as their only source of fluid, enhanced most of the endogenous antioxidant enzymes activity as glutathione reductase [GR], superoxide dismutase [SOD] and total antioxidant capacity [TAC] and produced a pronounced hypoglycemic effect as well as the amelioration of most of the studied biochemical parameters in STZ-induced diabetic rats, which confirmed by histo-pathological examination of different body organs, The potential antioxidant and hypoglycemic activities of guava leaves extract, respectively, are attributed to the presence of relatively high percentage of phenolic compounds [456 +/- 10.4 mg gallic acid equivalent/L] and other active volatile compounds with high antioxidant activity. Egyptian guava aqueous extract is effective in controlling hyperglycemia, reducing diabetic complications arising due to oxidative stress in diabetic rats, improve lipid metabolism as well as amelioration of the associated biochemical parameters