The Role of Hydrogen Bond Donor on the Extraction of Phenolic Compounds from Natural Matrices Using Deep Eutectic Systems.

Duarte Rente,Alexandre Paiva,Ana Rita Duarte

doi:10.3390/molecules26082336

Duarte Rente, Alexandre Paiva + Show 1 more

Open Access

https://doi.org/10.3390/molecules26082336

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Abstract

Recently, deep eutectic systems (DESs) as extraction techniques for bioactive compounds have surfaced as a greener alternative to common organic solvents. In order to study the effect of these systems on the extraction of phenolic compounds from different natural sources, a comprehensive review of the state of the art was carried out. In a first approach, the addition of water to these systems and its effect on DES physicochemical properties such as polarity, viscosity, and acidity was investigated. This review studied the effect of the hydrogen bond donor (HBD) on the nature of the extracted phenolics. The effects of the nature of the HBD, namely carbon chain length as well as the number of hydroxyl, methyl, and carbonyl groups, have shown to play a critical role in the extraction of different phenolic compounds. This review highlights the differences between DES systems and systematizes the results published in the literature, so that a more comprehensive evaluation of the systems can be carried out before any experimental trial.

Highlights

Most phenolic compounds are secondary metabolites [1], found in a wide number of plants, fruits, and vegetables, that are responsible for plant growth and development while displaying sensorial, structural, and defensive properties [2,3]
Since the physicochemical properties such as density, viscosity, polarity, pH, etc. of deep eutectic systems (DESs) are a result of the molecular interactions [58] between the hhyydrogen bond acceptor (HBA) and the hydrogen bond donor (HBD), and a wide range of HBDs have been used for extraction, the functional group of the HBD was used as a reference to interpret the results reported in the literature, as it methanol, which were used for comparison purposes
Since the physicochemical properties such as density, viscosity, polarity, pH, etc. of DESs are a result of the molecular interactions [58] between the HBA and the HBD, and a Moleculwes 2i0d2e1, 2r6a, n23g36e of HBDs have been used for extraction, the functional group of the HBD was 8 of 32 used as a reference to interpret the results reported in the literature, as it influences the final physicochemical properties of the systems

Summary

Introduction

Most phenolic compounds are secondary metabolites [1], found in a wide number of plants, fruits, and vegetables, that are responsible for plant growth and development while displaying sensorial, structural, and defensive properties [2,3]. The synthesis of phenolic compounds is done through organic synthesis, which usually requires the preparation of intermediary species and multiple reaction steps These individual steps require long reaction times, high temperatures, the use of toxic and harmful reagents, and the need for further purification in order to remove unwanted by-products and waste material, resulting in low yields [12]. For natural sources such as plant and vegetable matrices, an extraction step is required to obtain the desired compounds. There are a wide variety of natural matrices, ; wastes from the agricultural and food industries [13] such as wine lees and olive pomace [14,15,16,17] can be used as source materials, reducing

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