Endocrine Abstracts

Associated with the increased generation of free radicals and reduced activity of antioxidant system, oxidative stress is a pathogenetic mechanism underlying the onset of diabetic complications. Antioxidants are known to facilitate normalization of lipid peroxidation, composition, structures and functions of biological membranes. Antioxidants are universal membrane-trophic agents protecting against damaging factors. Plant antioxidants play a significant role in treatment of diabetes mellitus (DM).

The work was initiated to study oxidative stress in experimental DM and its correction with natural antioxidants.

Materials and methods

Antioxidant properties of medications based on phenolic compounds isolated from the leaves of cotton Gossypium hirsutum L. (gossitan) and euphorbia Euphorbia Fergansis (euphorbin), as well as extract of safflower Carthamus tinctorius blossoms and quercetin were studied in the models of adrenaline autoxidation and ascorbate-dependent lipid peroxidation in vitro. Hypoglycemic effects of the medications were studied in the experimental model of alloxan diabetes in rats. Blood glucose reaching more than 9–11 mmol/l, the medications and gliclazide, a commercially available blood glucose lowering drug (Servier, France), as a control at the recommended dose o.d. for 10 days were administered to the animals by a gastric tube. The orthotoluidine test was used to measure blood glucose. Activity of the rat liver glucokinase was calculated by changes in concentrations of exogenous glucose in % to the control upon the 30-minute incubation with the liver homogenates from rat with alloxan diabetes before and after the 10-day administration of polyphenols.

Results

Demonstrating high antioxidant activity, gossitan, euphorbin, safflower extract and quercetin were found to cause reduction in blood glucose concentrations in animals with experimental diabetes, associated with a reduction in free-radical lipid oxidation and an increase in activity of enzymes involved in glucose utilization. The medications demonstrated significantly higher antidiabetic effect than gliclazide. The combination of antioxidative and hypoglycemic effects in the medications under study would make possible correction not only of glycemia, but also of the free-radical processes taking place in diabetes mellitus to decrease the risk of onset and progression of diabetic complications.