The in vitro screening for hypoglycemic and antihypertensive activities of Dipsacus fullonum L

Abstract

The aim of the present study was to evaluate the hypoglycaemic and antihypertensive activities of Dipsacus fullonum L. (Dipsacaceae). The genus Dipsacus characteristically contains iridoid glucosides [1], triterpene glycosides [2], alkaloids [3] and other constituents [4]. The aerial parts of D. fullonum (1.056kg) were exhaustively extracted with methanol at room temperature (yield 7.59%). In order to separate the chemical compounds in function of their polarity, the crude extract was dissolved in distilled water and partitioned with n-hexane (yield 0.41%), chloroform (yield 0.5%), ethyl acetate (yield 0.32%) and n-butanol (yield 1.27%). The Angiotensin Converting Enzyme (ACE) inhibitory activity was measured trough the cleavage of the chromophore-fluorophore labelled substrate dansyltriglycine by ACE preparation from rabbit lung (EC 3.4.15.1) into dansylglycine which is quantitatively measured by HPLC. The most effective fractions were obtained in chloroform and n-butanol which gave 74.68% and 75.35% inhibition at 300µg/ml. Hypoglycaemic effects were examined using the in vitro assay based on the inhibition of α-amylase. Inhibitors of this enzymes delay carbohydrate digestion and prolong overall carbohydrate digestion time, causing a reduction in the rate of glucose absorption and consequently blunting the post-prandial plasma glucose rise. The ethyl acetate fraction was the most active with an IC50 value 48.44µg/ml. The inhibitory activity of n-hexane and chloroform fractions was weaker with IC50 values of 310.66 and 293.82µg/ml, respectively. Further fractionations will be required to identify the major active constituents.