EXPLOITING NATURAL DEEP EUTECTIC SOLVENT FOR THE EXTRACTION OF BIOACTIVE COMPOUNDS FROM PLANTS

In recent years, the increasing attention on green chemistry has led to the implementation of more sustainable chemical procedures, materials and products. In particular, the research of greener extraction techniques has been promoted by exploring more environmentally friendly alternatives compared to the conventional processes that have traditionally been used. There has also been an increasing interest in utilizing natural matrices and biomasses to recover natural bioactive compounds to be potentially employed in food supplements and nutraceuticals. In view of the above, this study was focused on extracting phenolic compounds from Vitis vinifer L. pruning by using a specific food-grade NADES system (betaine : lactic acid 1:5 + 20% H2O) as a green extraction solvent comparing its extraction performance to the use of a conventional organic solvent (methanol). Optimization of non-conventional solid-liquid extraction procedures, i.e. ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE), and operative conditions (temperature, time, amount of green pruning residues, water amount and solvent/sample ratio) was conducted, proving MAE, carried out at moderate temperatures and at short extraction time, to be a good method to extract phenolic compounds from this plant material. Traditional organic solvents produce a higher amount of waste and cause environmental and health concerns because of their volatility and toxicity. In contrast, the use of NADES is more advantageous because of the reduced number of extraction steps as well as amount of solvents needed and waste generated, their non-toxicity and the obtaining of safer and superior products. The greenness of NADES-based extractions was indeed confirmed with AGREEprep, a metric tool specifically developed to measure the greenness of sample preparation. Furthermore, NADES exhibited a better extraction performance on green pruning residues, compared to the methanolic solvent, as demonstrated by the HPLC-PDA analysis of selected marker compounds. However, since the NADES could not be removed from the phytocomplex, these target compounds resulted to be less concentrated than in the dried extract obtained after evaporation of the methanolic solvent. The bioactivity of these extracts was tested by preliminar in vitro spectrophotometric assays to assess the well-known antioxidant activity of phenolic compounds. A superior antioxidant activity was detected in the pure phytocomplex through radical scavenging colorimetric assays. Nonetheless, NADES-based extracts obtained from MAE showed a remarkable antioxidant power. In addition, the potential inhibition activity towards enzymes involved in metabolic diseases of these extracts was tested by in vitro colorimetric assays on α-glucosidase and pancreatic lipase, which are target enzymes of type 2 diabetes mellitus and anti-obesity treatments, respectively. Specifically, the pure phytocomplex and NADES-based extracts showed a lower inhibitory effect on α-glucosidase compared to that of a standard antidiabetic drug (acarbose). The dried extract and NADES-based extracts did not show an inhibitory effect on pancreatic lipase. In view of all these outcomes, NADES-based extracts demonstrated that they could effectively be employed in nutraceutical products