Alpha-glucosidase inhibition and antihyperglycemic activity of flavonoids rich fractions of Rosmarinus officinalis in normal and streptozotocin diabetic mice

Abstract

The aim of the present study was to evaluate the antihyperglycemic effect of flavonoids rich fractions of Rosmarinus officinalis L. namely n-butanol fraction (BUT) and diethyl ether fraction (D.E). Antihyperglycemic action was studied in vitro through the inhibitory tests on α-glucosidase of Saccharomyces cerevisiae. In vivo, the antidiabetic effects were tested in both normal and streptozotocin (STZ) induced diabetic mice using various tests including: the decrease of post prandial hyperglycemia, oral glucose tolerance test (OGTT), hypoglycemic effect and inhibition of glucose intestinal transporters. The in vitro α-glucosidase inhibition activity showed that both fractions (BUT and D.E) presented a potent effect. The maximum inhibition with D.E and BUT fractions was, 77 and 72% at 250 μg/ml, respectively. In vivo, BUT fraction at 800 mg/kg, showed a significant impact on post prandial hyperglycemia with 40.77% and 28.2% as a maximum glucose level reduction using sucrose and maltose, respectively. In OGTT, the maximum antihyperglycemic effect (51.65%) was also obtained with BUT fraction at 800 mg/kg. When testing the impact on glucose intestinal transport, a dose of 800 mg/kg of D.E fraction exhibited a significant inhibition with 24.12% as a maximum reduction. The present results clearly demonstrated the complementary effect of Rosmarinus officinalis flavonoids rich fractions, resulting to α-glucosidase inhibition and to antihyperglycemic action through glucose transport inhibition and blood glucose level reduction.