Flavonoid-rich fraction of Monodora tenuifolia Benth seeds improves antioxidant status in male Wistar rats with streptozotocin-induced Diabetes mellitus

Oxidative stress is a disruption in the balance between free radicals and the body's natural defenses. This study investigated the modulatory effect of a flavonoid-rich fraction of Monodora tenuifolia seed (FRFMTS) on oxidative stress and antioxidant enzymes in diabetic Wistar rats. The plant seeds were collected, and identified then, hydro-ethanolic extract was obtained with 80 % (v/v) ethanol and partitioned with solvents to obtain the FRFMTS. Diabetes mellitus was induced with a single dose of 40 mg/kg bwt streptozotocin and the rats were treated according to their grouping; group 1: non-diabetic control, groups 2 and 3: non-diabetic treated with 25 mg/kg FRFMTS and 50 mg/kg FRFMTS, respectively. Group 4: diabetic control group, groups 5 and 6: diabetic groups treated with 25 mg/kg and 50 mg/kg FRFMTS, respectively, while group 7: diabetic treated with 6.67 mg/kg metformin. Antioxidant status, oxidative stress biomarkers and activities of antioxidant enzymes were determined in plasma, heart, and kidney tissues using established procedures. Plasma total antioxidant status (TAS) was increased significantly (p < 0.05) in diabetic rats upon treatment with 25 mg/kg FRFMTS (70.4 %), while 50 mg/kg FRFMTS increased TAS by 70 %. The activities of glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD) in the plasma, heart, and kidney of diabetic rats significantly decreased (61.3 %, 58.8 % and 31.4 % respectively) while lipid peroxidation (LPO) was elevated when compared with normal control groups. Flavonoid-rich fraction of M. tenuifolia at 25 mg/kg bwt and 50 mg/kg bwt significantly increased the activity GPx enzyme by 32.3 % and 72 % in plasma, while there was no significant differences in both kidney and heart of diabetic rats when compared with diabetic control groups. The treatment of diabetic rats with 25 mg/kg FRFMTS and 50 mg/kg FRFMTS improved SOD activity in the plasma (51.5 % and 69.8 %), heart (32.3 % and 27.6 %) and kidney (31.4 % and 27.1 %) respectively, and CAT activity in plasma (44.2 % and 57 %), heart (28.6 % and 60 %) and kidney (69.6 % and 76.7 %) respectively. The concentration of malondialdehyde (MDA) in lipid peroxidation assay in the heart and kidney of diabetic rats treated with 25 mg/kg FRFMTS and 50 mg/kg FRFMTS reduced significantly by (62.5 % and 71.1 % in heart), while 50 mg/kg FRFMTS significantly reduced MDA in kidney by 43.8 %. The results showed that FRFMTS reduces oxidative stress and enhances the activities of antioxidant enzymes in STZ-diabetic Wistar rats. As such, FRFMTS could be useful in the management of oxidative stress-mediated diabetic complications.