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

Background

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.

Results

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 %.

Conclusions

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.