Fatty Acid Composition, Total Sugar Content and Anti-Diabetic Activity of Methanol and Water Extracts of Nine Different Fruit Tree Leaves Collected from Mediterranean Region of Turkey

In this research, the total sugar content, fatty acid compositions, and α-amylase and α-glucosidase inhibitory activity of methanolic and water extracts of nine different fruit tree leaves were determined. α-amylase and α-glycosidase inhibitory activity were determined by using Caraway-Somogyi iodine/potassium iodide and 4-nitrophenyl-α-D-glucopyranoside as substrate, respectively. The total sugar content of the nine different fruit tree leaves varies from 281.02 mg GE/g (glucose equivalents) to 643.96 mg GE/g. Methanolic extract from avocado leaves had the strongest in α-amylase and α-glucosidase inhibitory activity, 69.21 and 96.26%, respectively. Fatty acid composition of nine fruit tree leaves was characterized by gas chromatography and 24 components were identified. Among the tested fruit tree leaves, the main component was linolenic acid (49.09%). The level of essential fatty acids are over 50% in mulberry, grape, and loquat leaves. Polyunsaturated fatty acids were the major group of fatty acids present in oils of mulberry, fig, pomegranate, grape, and loquat leaves. Therefore, these oils can be considered as a good source of polyunsaturated fatty acids. Furthermore, avocado can be regarded as a new source for diabetic therapies.