Natural deep eutectic solvents as beneficial extractants for enhancement of plant extracts bioactivity

• Grape skin phenolics were successfully extracted with deep eutectic solvents.
• Deep eutectic solvents are more effective as extraction solvents than methanol.
• Applied deep eutectic solvents possesses low cytotoxicity toward tumour cell lines.
• Proper choice of extraction solvent could enhance plant extract bioactivity.

In the present study phenolic grape skin extracts were prepared by using five choline chloride based natural deep eutectic solvents (NADESs) containing glucose, fructose, xylose, glycerol, malic acid and valorised by testing their biological activity in vitro using two human tumour cell lines (HeLa and MCF-7). Initially, used NADESs were investigated regard to their toxicity and low cytotoxicity of solvents was observed toward HeLa and MCF-7 cells (EC50 values > 2000 mg/L). Among used choline chloride based NADESs, the one containing malic acid showed the best performance concerning extraction efficiency (total phenolic and total anthocyanin were 91 and 24 mg/g dw), as well as antioxidant (ORAC values were 371 μmol TE/g dw) and antiproliferative activity (percentage of cell viability were about 20%). Herein, for the first time it was showed that NADES components could be chosen not only to fine-tune solvent physicochemical characteristics but also to enhance biological activity of extracts prepared in NADESs. Therefore, our research confirmed that NADESs are excellent and promising choice of solvents for sustainable and green extraction, which will lead to its novel application in food and pharmaceutical industry.