Contribution of the glucosinolate fraction to the overall antioxidant potential, cytoprotection against oxidative insult and antimicrobial activity of Eruca sativa Mill. leaves extract

Background: Eruca sativa Mill. (Brassicaceae) is commonly utilized as ingredient in salads and also as a folk remedy to treat various diseases. Objective: To establish the contribution of the glucosinolate (GLS) fraction to the overall antioxidant, cytoprotective against oxidative insult and antimicrobial properties of the hydro-alcoholic extract of E. sativa leaves from Sicily (Italy), phytochemically characterised. Materials and Methods: The antioxidant activity was evaluated by different in vitro systems. The cytoprotective effect against H2O2-induced oxidative stress was tested in human peripheral blood mononuclear cells (PBMCs). The antimicrobial potential against bacteria and fungi was assayed by standard methods. Results: E. sativa extract exhibited both radical scavenging (IC50 1.04 ± 0.04 mg/mL) and ferrous ions chelating activity (IC50 0.327 ± 0.0032 mg/mL), and mild reducing power; the GLS fraction showed chelating ability only (IC50 0.225 ± 0.009 mg/mL). In the experimental model of H2O2-induced oxidative stress in human PBMCs, a significant cytoprotective effect and a suppression of ROS production by both extract and GLS fraction were observed (p<0.001). E. sativa extract displayed moderate antimicrobial activity against Gram-positive bacteria, and Staphylococcus aureus was the most sensitive strain (MIC 0.125 mg/mL), whereas the GLS fraction was not active. Conclusion: GLSs are not involved in the primary antioxidant activity of E. sativa leaves extract, but they are, almost in part, responsible for its ferrous ion chelating properties. Iron chelating compounds contained in E. sativa extract may protect cells under conditions of oxidative stress, and GLSs might play a chief role in this effect.