Effects of certain natural phenolic compounds on experimental diabetes and diabetic complications of smooth muscles

In this thesis, diabetic complications developed in isolated aorta, Vas deferens, gastric fundus and ileum from rats with streptozotocin (STZ)-induced diabetes for 6 weeks and effects of 3 weeks treatment with p-OH benzoic acid, protocatechic acid and gallic acid, which have antioxidant activities with increasing potency order related to their hydroxyl number, were investigated on the development of these complications by using isolated organ experiments. In STZ-diabetic rats for 6 weeks, hyperglycemia was developed, water and food consumptions along with urine and feces outputs were increased and body weights decreased. Protocatechic acid prevented significant increases in food consumption and feces output due to diabetes. In diabetic animals, responses of isolated organs, aorta to phenylephrine, Vas deferens to phenylephrine and acetylcholine, ileum to acetylcholine were found to be increased, while responses of gastric fundus to serotonin were observed to be decreased. It was found that the in vivo administration of p-OH benzoic acid, protocatechic acid and gallic acid inhibited, unchanged or promoted the changes occurred in smooth muscles, and sometimes, they caused alterations in unchanged smooth muscle activity due to diabetes relative to control animals. On the basis of these findings, it was concluded that by p-OH benzoic acid, protocatechic acid and gallic acid exhibit the improving or impairing effects in a manner independent of their antioxidant power and from diabetic complications and they may exhibit prooxidant activities in the experimental conditions applied.