Application of Deep Eutectic Solvents (DES) for Phenolic Compounds Extraction: Overview, Challenges, and Opportunities

Abstract

The green chemistry era has pushed the scientific community to investigate and implement new solvents in phenolic compounds (PC) extraction as alternatives to organic solvents, which are toxic and may be dangerous. Recently, deep eutectic solvents (DES) have been applied as extraction solvents for PC. They have the advantages of biodegradability and ease of handling with very low toxicity. Nevertheless, the extraction process is affected by several factors: affinity between DES and the target compounds, the water content, the mole ratio between DES' starting molecules, the liquid/solid ratio between the DES and sample, and the conditions and extraction method. On the other hand, PC recovery from DES is a challenge because they can establish a strong hydrogen bond network. Alternatively, another possibility is to use DES as solvent extraction as well as formulation medium. In this way, DES can be suitable for cosmetics, pharmaceutical, or food applications.

Deep eutectic solvent‐based extraction of polyphenolic antioxidants from onion (Allium cepa L.) peel

“…A bed of 11 cm was prepared with pretreated hydrated Amberlite XAD‐16 resin (2 g) in a column of 1 cm inside diameter; 5 mL of DES extract was introduced drop wise in the column and, after this, eluted with 100 mL distilled water until the DES was washed out. Deep eutectic solvent could be eluted with water because of DES polarity and dissolubility . The column was finally eluted with 98% methanol (100 mL) because phenolic compounds are recovered with methanol solution.…”

“…Hence, DESs have a strong potential for extracting phenolic compounds. A recent review article elaborates on the separation of phenolic compounds (PCs) from DESs . To recover a PC from a DES, liquid–liquid extraction using another solvent, solid–liquid extraction using resin, and precipitation by addition of antisolvents are widely applied.…”

Enhanced extraction of phenolic compounds using choline chloride based deep eutectic solvents from Juglans regia L.

“…Nowadays, this idea is being expanded to create designer solvents, using several combinations of HBA and HBD, with tunable properties to selectively dissolve and extract natural and bioactive compounds from plants, oils or biomass, valorizing natural products or wastes as a source of valuable compounds (Dai et al, 2016;Nam et al, 2015;Paradiso et al, 2016). A very recent review on the application of deep eutectic solvents for the extraction of phenolic compounds can be found in literature, describing the possibility of using DES both as solvent and formulation media with potential cosmetics, pharmaceutical, or food applications (Ruesgas-Ramón et al, 2017).…”

Deep eutectic solvents used as extraction solvent for the determination of flavonoids from Camellia oleifera flowers by high‐performance liquid chromatography

“…The DESs could be easily prepared by the heating method based on the previously published procedure. 32,33 Different kinds of hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs) were mixed in suitable molar ratio and heated at 80°C with constant stirring (DF-101S heating magnetic stirrer, Yuhua Instrument Co., Ltd, Gongyi, China) until the formation of an homogeneous liquid. In this work, 13 kinds of DESs were synthesised as displayed in Table 1, and the structures of different DESs are illustrated in Figure S2.…”

“…According to the literature surveys, the extraction efficiency of DESs based on the acid-, alcohol-and amide-were better than those based on sugar for flavonoids. 22,33,34 In this research, we chose choline chloride and L-proline as the HBAs and three types of HBDs (acid, alcohols, amides) to prepare DESs. Then, the extraction yields of different DESs and the commonly used solvents were compared.…”