Antihyperglycemic effect of protocatechuic acid on streptozotocin-diabetic rats

Protocatechuic acid (PCA) (3,4-dihydroxybenzoic acid), a natural phenolic compound found in many edible and medicinal plants, is a major benzoic acid derivative with a strong antioxidative effect, 10-fold higher than that of alpha-tocopherol. The present study is aimed at evaluating the antidiabetic effect of PCA on STZ-diabetic rats. Diabetes was induced in male albino Wistar rats by the administration of STZ (40 mg/kg BW, i.p.). PCA was administered orally at three different doses (50, 100, 200 mg/kg BW/day) to STZ-diabetic rats for 45 days. Diabetic rats showed increase in plasma glucose and glycosylated hemoglobin (HbA1c) and a decrease in plasma insulin and hemoglobin (Hb). The activities of gluconeogenic enzymes like glucose 6-phosphatase and fructose 1,6-bisphosphatase increased whereas the glycolytic enzyme glucokinase decreased in the liver along with glycogen content. The oral administration of PCA or glibenclamide in saline, for 45 days, prevented the changes and improved toward normalcy. No significant effect was observed in normal rats treated with PCA. Thus, our results show that PCA at 100 mg possesses a potential antihyperglycemic effect that is comparable with glibenclamide.