In Vitro Antidiabetic Evaluation of Cucurbitacins from Mauritanian Citrullus Colocynthis Leaves

Abstract

This study was carried out on Citrullus colocynthis (L.) Schrad leaves, which is a medicinal plant known locally in Mauritania for its antidiabetic effects. In this work, we identified five triterpenes: cucurbitacin E, cucurbitacin E glucoside (CEG), cucurbitacin I glucoside (CIG), cucurbitacin L glucoside (CLG) and Khekadaengoside K. Khekadaengoside K was identified for the first time in the leaves of Citrullus colocynthis. All compounds were isolated from the methanolic extract except cucurbitacin E which was isolated from the dichloromethane extract. Cucurbitacin E glucoside is the major product with a yield of 11.3 mg/g (This yield is approximately tenfold greater than previously reported values). The isolated products were evaluated for their antidiabetic activities for the first time via in vitro tests against α-amylase (compounds were isolated independently and then tested). The best activity was observed with CEG (IC₅₀ = 1378.14 ± 126.67 µM). In addition to isolated compounds, crude extracts (extraction with dichloromethane followed by another with methanol) were also assessed with α-amylase inhibition assay. These assays showed a greatest activity for the methanolic extract (IC₅₀ = 0.69 ± 0.04 mg/mL).