The fatty acid-rich fraction of Eruca sativa (rocket salad) leaf extract exerts antidiabetic effects in cultured skeletal muscle, adipocytes and liver cells

Abstract

Context: Eruca sativa Mill. (Brassicaceae), commonly known as rocket salad, is a popular leafy-green vegetable with many health benefits. Objective: To evaluate the antidiabetic activities of this plant in major insulin-responsive tissues. Materials and methods: Five E. sativa leaf extracts of varying polarity were prepared (aqueous extract, 70% and 95% ethanol extracts, the n-hexane-soluble fraction of the 95% ethanol extract (ES3) and the defatted 95% ethanol extract). Eruca sativa extracts were investigated through a variety of cell-based in vitro bioassays for antidiabetic activities in C2C12 skeletal muscle cells, H4IIE hepatocytes and 3T3-L1 adipocytes. Guided by the results of these bioassays, ES3 was fractionated into the saponifiable (SM) and the unspaonifiable (USM) fractions. Glucose uptake was measured using [3H]-deoxy-glucose, while the effects on hepatic glucose-6-phosphatase (G6Pase) and adipogenesis were assessed using Wako AutoKit Glucose and AdipoRed assays, respectively. Results: ES3 and its SM fraction significantly stimulated glucose uptake with EC50 values of 8.0 and 5.8 µg/mL, respectively. Both extracts significantly inhibited G6Pase activity (IC50 values of 4.8 and 9.3 µg/ mL, respectively). Moreover, ES3 and SM showed significant adipogenic activities with EC50 of 4.3 and 6.1 µg/mL, respectively. Fatty acid content of SM was identified by GC-MS. trans-Vaccenic and palmitoleic acids were the major unsaturated fatty acids, while palmitic and azelaic acids were the main saturated fatty acids. Discussion and conclusion: These findings indicate that ES3 and its fatty acid-rich fraction exhibit antidiabetic activities in insulin-responsive cell lines and may hence prove useful for the treatment of type 2 diabetes.