Screening For α-Amylase Inhibitory Activity Of Crataegus And Rubus Genera In Syria, Isolation And Identification Of The Active Principle

Abstract

One of the treatment strategies for diabetes mellitus is to inhibit specific digestive enzymes in order to reduce carbohydrates absorption in the intestines. In this study, inhibitory activity toward the α-amylase enzyme were determined for the methanolic extracts of the leaves of two species of the genus Crataegus; monogyna, and azarolus var aronia, and three species of the genus Rubus; sanctus, hedycarpus, and collinus. The leaves were collected during spring and autumn seasons from different regions across the Syrian Arab Republic. The methanolic extract of C.azarolus var aronia harvested in autumn exhibited the strongest inhibitory activity toward α-amylase compared to the other extracts with an IC50=103 µg/ml. For a closer look into this plant, the dry methanolic extract was suspended in water and extracted (liquid-liquid) using diethyl ether and ethyl acetate as extracting solvents. Due to the promising inhibitory activity of the ethyl acetate extract toward α-amylase with an IC50=96 µg/ml, this extract was further fractionated by means of preparative HPLC. The structure of the isolated compound that revealed the strongest inhibitory activity toward α-amylase enzyme (IC50=84 µg/ml) was elucidated using nuclear magnetic resonance (NMR), and mass spectroscopy (MS) techniques. The structure was identified based on MS and NMR data to be (–)-Epicatechin, a biologically active flavan-3-ol compound