Biocompatible Deep Eutectic Solvents Based on Choline Chloride: Characterization and Application to the Extraction of Rutin from Sophora japonica

Abstract

The development of novel green solvents has been one of the hottest subjects in green chemistry. Deep eutectic solvents (DESs) have logically and naturally emerged in the search for more biocompatible and biodegradable solvents. In this study, some basic physical properties, including viscosity, conductivity and density, of twenty DESs prepared from choline chloride and various hydrogen bond donors were investigated systematically. In addition, the biocompatibility of the tested DESs was qualitatively and quantitatively evaluated using two gram-positive (Staphylococcus aureus and Listeria monocytogenes) and two gram-negative (Escherichia coli and Salmonella enteritidis) bacteria. A Closed Bottle Test was used to assess the biodegradability of these DESs. The results demonstrated that these choline chloride-based DESs were excellent solvents with extremely low toxicity and favorable biodegradability. Finally, DESs were used to extract a flavonoid (rutin) from the flower buds of Sophora japonica. An extraction efficiency of 194.17±2.31 mg·g −1 was achieved using choline chloride/triethylene glycol containing 20% water. The excellent properties of DESs indicate their potential as promising green solvents for the extraction of rutin with favorable prospects for wide use in the field of green technology. acid, levulinic acid, malonic acid, malic acid, citric acid, tartaric acid, xylose, sucrose, fructose, glucose, and maltose (all ≥99% mass fraction purity) were all purchased from Tianjin Kermel Chemical Reagent Co., Ltd. (Tianjin, China). Rutin (≥98% mass fraction purity) was purchased from Shanghai Yuanye Biotechnology Co., Ltd. (Shanghai, China). S. japonica bud was purchased from ZhanJiang Yizhou Medicines Co., Ltd. (Guangdong, China). All other chemicals were of analytical grade.Preparation of DESs. DESs were synthesized by mixing choline chloride and HBDs at a defined molar ratio (see Table 1) and heating at 100 °C for 2-4 h at an atmospheric pressure under constant stirring until a stable homogeneous liquid was formed. 21 Sugar-based DESs were prepared using the same conditions but under a nitrogen atmosphere. All the prepared DESs were allowed to cool to room temperature and dried in a vacuum oven at 50 °C for 24 h.The solvents were stored in sealed laboratory vials and kept in a desiccator. Physical Properties. The water contents of the samples were measured using a Metrohm Karl-Fischer (model 890) titrator. The viscosities of the DESs were measured with a HAAKE RheoStress 600 at 100 Hz from 25-80 °C at a rate of 5 °C min −1 . The conductivity of all samples was measured with a conductivity meter (Shanghai Leici DDS-307A) at a preset temperature.The densities of all samples were determined using a 5 cm 3 pycnometer calibrated with deionized water at 30 °C. As for the determination of viscosities, conductivity and densities, all the DESs except sugar-based DESs were dried at 100 °C to minimize the water content. All measurements were performed at constant temperature. The relative standard deviation for all th...

Optimization of the Process Conditions for the Extraction of Rutin from <i>Ruta graveolens </i>L. by Choline Chloride Based Deep Eutectic Solvents

“…According to the data available in the literature, viscosities and/or densities for the investigated DESs are as follows: ChCl : fructose [12]. Addition of 25% and 50% of water significantly improved rutin extraction in all experiments, which could be attributed to the decrease in the viscosity of the DESs by addition of water, as described by Duan et al [6] and Zhao et al [11]. When rutin extraction yields are compared, there is no significant difference among the experiments performed with addition of 50% and 25% of water with the same DES, and, as indicated in Figure 1, there is no need to perform the extraction for 3 or 6 h.…”

“…All DESs were prepared as described in the previous literature [11]. Choline chloride (ChCl) as HBA was mixed with HBD in a certain ratio as stated in Figure 1.…”

The effect of deep eutectic solvents on the asymmetric hydrolysis of styrene oxide by mung bean epoxide hydrolases

“…Racemic PED and SO were purchased from Guangzhou Qiyun bioscience Co. Ltd. All other reagents used to synthesize DESs were of analytical grade and were from commercial sources. The preparation of DESs was referenced by previous literature (Zhao et al 2015). Briefly, choline chloride and hydrogen bond donor were mixed at a fixed molar ratio at 80 °C for appropriately 2 h until the formation of a stable homogeneous liquid.…”

Deep Eutectic Solvents: An Overview of its Application as a “Green” Extractant

“…quaternary ammonium salts are readily available. 4 Design for degradation Most of the components of DES are biodegradable [31] and as such do not persist in the environment for a longer period of time. For example, cholinium alkanoates based DESs are environmentally benign and biodegradable [32,33].…”

“…Zhao et al, [31] investigated the extraction of flavonoid from the flower buds of Sophora japonica using several choline based deep eutectic solvents. It was found that eutectic solvents based on choline/triethylene glycol can be efficiently used as a potential green solvent for the removal of rutin in sophora japonica with an extraction efficiency of 194.17 ±2.31 mg.g -1…”