ABSTRACT

In-vivo antidiabetic activity of Cydonia oblonga Mill. (quince) leaves, Helianthus tuberosus L.(Jerusalem artichoke) tubers, and Allium porrum L. (leek) bulb and leaves was determined in our previous studies. These plants are tradi-tionally used to lower blood glucose levels in Turkey. Therefore, inhibitory activities of quince leaves, Jerusalem artichoke tubers, leek bulbs and leaves on carbohydrate digestive enzymes (α-glucosidase and α-amylase) were investigated to enlighten the mechanism of action. On the other hand, their antioxidant activities, total phenol and flavonoid contents were investigated. The highest ABTS radical scavenging, total antioxidant activity and reducing power were found in C. oblonga leaf ethanol extract. Nevertheless, tested plant extracts did not inhibit α-amylase and α-glucosidase significantly. Total phenol and flavonoid contents of the extracts were found in the range of 7.91-163.33 mg gallic acid equivalent/g and 27.26-29.60 mg quercetin/g, respectively. Consequently, it is clearly seen that the mechanism of action of these three plants was not determined to be related to the inhibition of α- amylase and α-glucosidase enzymes.