Usual extraction processes for analyzing foods, supplements, and nutraceutical products involve massive amounts of organic solvents contributing to a negative impact on the environment and human health. In recent years, a new class of green solvents called natural deep eutectic solvents (NADES) have been considered a valid alternative to conventional solvents. Compared with conventional organic solvents, NADES have attracted considerable attention since they are sustainable, biodegradable, and non-toxic but also are easy to prepare, and have low production costs. Here we summarize the major aspects of NADEs such as the classification, preparation method physicochemical properties, and toxicity. Moreover, we provide an overview of novel extraction techniques using NADES as potential extractants of bioactive compounds from foods and food by-products, and application of NADEs in food analysis. This review aims to be useful for the further development of NAES and for broadening the knowledge of these new green solvents in order to increase their use for the extraction of bioactive compounds and in food analysis.

Okra is a vegetable crop very popular in tropical, subtropical, and warm temperate regions of the world for its edible fruit. Nowadays, this species can be easily found in European local markets, as a basic ingredient in many local and traditional dishes. Considering the extensive and spread use of okra fruits, to achieve deep insight on its chemical composition the analysis of the polar extract by high-performance liquid chromatography coupled to multiple-stage linear ion-trap and orbitrap high-resolution mass spectrometry in negative electrospray ionization mode was carried out. By this approach, 39 metabolites belonging to different polar lipid classes, such as oxylipins, phospholipids, glycolipids, and sphingolipids, were putatively identified for the first time in A. esculentus. Moreover, LC-HRMS/MS analyses guided the isolation and characterization by NMR experiments of 19 specialized metabolites belonging to phenolic acid and flavonoid classes, 8 of them never reported before in A. esculentus. Finally, antioxidant activity and inhibition of α-glucosidase activity were assayed, suggesting a good anti-oxidant anti-hyperglycemic activity for okra fruit.

The comparative chemical composition of different part of Faustrime fruits (peels, pulp, albedo, and seeds) extracted with different solvents was determined by GC-MS and UHPLC-HRMS QTof. The obtained data were also combined for their in vitro antioxidant activity by multivariate analysis to define a complex fingerprint of the fruit. The principal component analysis model showed the significative occurrence of volatile organic compounds as α-bisabolol and α-trans-bergamotol in the pulp and albedo, hexanoic acid in the seeds, and several coumarins and phenolics in the peels. The higher radical scavenging activity of the pulp was related to the incidence of citric acid in partial least square regression.

Valorisation of food by-products has recently attracted considerable attention due to the opportunities to improve the economic and environmental sustainability of the food production chain. Large quantities of non-edible parts of the artichoke plant (Cynara cardunculus L.) comprising leaves, stems, roots, bracts, and seeds are discarded annually during industrial processing. These by-products contain many phytochemicals such as dietary fibres, phenolic acids, and flavonoids, whereby the most challenging issue concerns about the recovery of high-added value components from these by-products. The aim of this work is to develop a novel valorisation strategy for the sustainable utilisation of artichoke leaves’ waste, combining green pressurised-liquid extraction (PLE), spectrophotometric assays and UPLC–HRMS phytochemical characterization, to obtain bioactive-rich extract with high antioxidant capacity. Multivariate analysis of the major selected metabolites was used to compare different solvent extraction used in PLE.

Currently, the interest of consumers towards functional foods as source of bioactive compounds is increasing. The sprouts of Raphanus sativus var longipinnatus (Brassicaceae) are “microgreens” popular, especially in gourmet cuisine, for their appealing aspect and piquant flavour. They represent a functional food due to their high nutritional value and health-promoting effects. Herein, the sprouts of daikon were extracted by different solvent mixtures to highlight how this process can affect the chemical profile and the antioxidant activity. An in-depth investigation based on a preliminary LC-ESI/LTQOrbitrap/MS profiling was carried out, leading to the identification of nineteen compounds, including glucosinolates and hydroxycinnamic acid derivatives. An undescribed compound, 1-O-feruloyl-2-O-sinapoyl-β-D-glucopyranoside, was isolated, and its structure was elucidated by NMR spectroscopy. The phenolic content and radical scavenging activity (DPPH and TEAC assays), along with the ability to activate Nrf2 (Nrf2-mediated luciferase reporter gene assay) of polar extracts, were evaluated. The results showed the highest antioxidant activity for the 70% EtOH/H₂O extract with a TEAC value of 1.95 mM and IC₅₀ = 93.97 µg/mL in the DPPH assay. Some 50% and 70% EtOH/H₂O extracts showed a pronounced concentration-dependent induction of Nrf2 activity. The extracts of daikon sprouts were submitted to ¹H NMR experiments and then analyzed by untargeted and targeted approaches of multivariate data analysis to highlight differences related to extraction solvents.

The increasing food waste generated along the food chain should be considered as a source of high-value compounds, with the aim of improving the circularity of productions. In this study, carrot pomace, the major by-product of carrot juice processing, was used as a source of carotenoids. For the valorisation of this by-product, different non-conventional extraction methods of carotenoids such as Ultrasound-Assisted Extraction (UAE) and Pressurised Liquid Extraction (PLE) have been developed. For the latter, the main parameters influencing the extraction have been optimised using a multivariate response surface design. Compared with previous reports, this study advances the current knowledge by using only food-grade ethanol/water mixtures as solvents and by combining the optimisation of carotenoid recovery with the measurement of energy consumption to evaluate process efficiency. Moreover, the sustainability of the extraction was quantitatively assessed using the AGREEprep metric, providing a more integrated and environmentally sound strategy for the valorisation of Daucus carota L. pomace.