## 4 DES in Extraction Processes of Bioactive Products  
DES, but more specifically, NADES based on natural compounds, have been selected as optimal solvents for extraction processes because of their properties [10; 16; 118]. NADES have superior solubilizing ability for natural products and are usually nonvolatile [16]. For example, [PERSON] et al. (2014) found that NADESs have been able to enhance the stability of the extracted phenolic compounds [119]. The biocompatibility of NADES with biomaterials has even generated interest in biotechnological industries since they are also suitable solvents for the extraction of natural bioactive compounds from different organisms with higher efficacy compared to the conventional ones, as shown in different previous reviews [12; 67]. Moreover, DES have been successfully used for the extraction of proteins very efficiently [120; 121]. For example, NADES are more useful as dissolving media in biological assays in substitution of DMSO [16]. In relation to health, we are going to focus our attention on some studies on the extraction of bioactive compounds from medicinal plants, although DESs have been widely used for the extraction of other kind of compounds, with different ranges of hydrophilicity. This is because DES and NADES can include different combinations of compounds, and molar ratios of each component can be modified, allowing for a wide range of tailored designs, apart from the development of innovative extraction techniques [16; 122; 123]. The most common solvents include choline chloride as a hydrogen bond acceptor [123]. It has been demonstrated that a higher efficiency can be obtained using them instead of conventional solvents. Most bioactive compounds extracted with them include flavonoids, phenolic acids, and anthocyanins [123]. These kinds of extractions involve plants such as _Chamaecyparis obtusa_[124], _Larrea cuneifolia_[125], _Cinnamum camphora_[126], or _Scutellaria bialensis_[127], among others. [PERSON] et al. published a review of the microextraction techniques such as liquid-phase microextraction; hollow-fiber liquid-phase microextraction; dispersive liquid-liquid microextraction methods; deep eutectic solvent based on an aqueous two-phase system; ultrasound; microwave extraction; vortex extraction; heating and stirring or solid-phase extraction. They presented the advantages and disadvantages of each extraction method and showed how several properties (melting point, density, viscosity, surface tension, pH, solubility, or polarity) could directly affect the extraction efficiency [24]. [PERSON] et al. presented an important summary where they showed some studies that have used DESs as the extraction solvent. They collected information regarding the used sample, extracted bioactive compounds from plants, fruits or vegetables, DES (molar ratio and water content), extraction method, and, finally, analytical technique [128]. The food and pharmaceutical industry have also explored the application opportunities of DES due to the potential use of extracts as food additives, mainly, or even as candidate pharmaceutical agents because of their antimicrobial and antioxidant activity [129; 130]. Therefore, extractions include the use of DESs with by-products of fruits such as grape skin or grape pomace or from onion seed and olive oil, tomato, or pear industries, among others [129; 131; 132]. This can be a way to revalorize agro-food industry waste or by-products. There is an additional application of NADES to increase food safety as reviewed by [PERSON] et al. (2019) or [PERSON] (2019) in an attempt to remove harmful toxins from food ingredients [130; 133]. A recent review carried out by [PERSON] showed a very good summary of several studies where some phenolic compounds were extracted from natural sources such as _Morus alba, Olea europaea, Junglas regia, Lycium barbarum, Citrus aurantium, Citrus paradise, Lonicena japonica Thumb, Camelia sinensis_, or _Citrus sinensis_, among others.