Extraction of Illegal Dyes from Red Chili Peppers with Cholinium-Based Deep Eutectic Solvents

Efficient Extraction of Flavonoids from Lotus Leaves by Ultrasonic-Assisted Deep Eutectic Solvent Extraction and Its Evaluation on Antioxidant Activities

The discovery of a green extraction solvent for natural plants could promote related research. In this study, deep eutectic solvents (DES) were used as green solvents coupled with an ultrasound-assisted extraction method (UAE) to extract flavonoids from lotus leaves. Thirty-four different DES were performed and choline chloride/urea with 40% water was chosen as the most promising one, and the related parameters in the procedures were optimized, resulting in the highest extraction amount of flavonoids in lotus leaves. D-101 was selected from four macroporous resins to separate the flavonoids from DES. Moreover, DES could be recycled and efficiently reused four times with satisfactory performances. In addition, the lotus leaf flavonoids from the DES extract exhibited antioxidant activities in five kinds of assays including DPPH, ABTS, Fe3+ reducing, FRAP, and Fe2+ chelating. It also showed antibacterial activities on Staphylococcus aureus and Escherichia coli bacterial strains with minimal inhibitory concentrations at 1666 μg/mL and 208 μg/mL, respectively. In the HPLC analysis, the three main components in the DES extract were identified as astragalin, hyperoside, and isoquercitrin. In conclusion, the developed UAE-DES followed by macroporous resin treatment could become an efficient and environmentally friendly extraction and enrichment method for flavonoids from lotus leaves and other natural products.

Phytomass Valorization by Deep Eutectic Solvents—Achievements, Perspectives, and Limitations

In recent years, a plethora of extraction processes have been performed by a novel class of green solvents known as deep eutectic solvents (DESs), possessing several environmental, operational, and economic advantages proven by experience when compared to organic solvents and ionic liquids. The present review provides an organized overview of the use of DESs as extraction agents for the recovery of valuable substances and compounds from the original plant biomass, waste from its processing, and waste from the production and consumption of plant-based food. For the sake of simplicity and speed of orientation, the data are, as far as possible, arranged in a table in alphabetical order of the extracted substances. However, in some cases, the isolation of several substances is described in one paper and they are, therefore, listed together. The table further contains a description of the extracted phytomass, DES composition, extraction conditions, and literature sources. With regard to extracted value-added substances, this review addresses their pharmacological, therapeutic, and nutritional aspects. The review also includes an evaluation of the possibilities and limitations of using DESs to obtain value-added substances from phytomass.

Ultrasound-assisted hydrophobic deep eutectic solvent based solid-liquid microextraction of Sudan dyes in spice samples

An environmentally friendly, simple method was carried out with the help of an ultrasonic assisted solid-liquid microextraction technique using a new deep eutectic solvent (DES) for the extraction and determination of Sudan dyes (I-IV) in spice samples. In this method, parameters affecting the optimization were researched and optimized such as DES composition, DES volume, ultrasonic time, temperature and, centrifuge time. The analytical performance of the developed method was quite satisfactory, the R² values were higher than 0.9989, and the limits of quantification were <1.17 μg g^-1. Two different concentrations (10-50 μg g^-1) were spiked to Chili peppers, paprika, cumin and sumac spices for the applicability and accuracy of the developed microextraction method. Some of these spices were found to contain Sudan I and IV dyes. The recovery values for spiked samples were found to be between 85.55% and 99.29% and relative standard deviations were found to be <3.17% when using a 10 μg g^-1 Sudan dyes concentration. The results showed that the developed method can be successfully applied for extraction and determination of Sudan dyes in spice samples.

New guidelines for testing "Deep eutectic solvents" toxicity and their effects on the environment and living beings

Deep eutectic solvents (DESs) were described at the beginning of this century as an alternative to ionic liquids (ILs) in green chemistry. Despite their obvious sustainable advantages as reaction media, there is still controversy about their potential toxicity. Most of the ecotoxicity assays done up to now involving DESs are based on antibiograms. This is not a good approach due to the high density and viscosity of most DESs already described. Additionally, antibiograms do not allow continuous monitoring of neither cellular growth nor changes on physicochemical parameters like culture acidification due to cellular growth or DESs metabolization. This work starts by displaying advantages and disadvantages of the DESs toxicity assays already reported. Then, using a new DES recently described and Escherichia coli as a model microorganism, liquid cultures with continuous monitoring of pH, temperature, shaking and optical density have been used, for the first time, to quantify potential toxicity of the DES as well as the degree of the cellular tolerance (in preadapted and non-preadapted cells). The results obtained show that this new DES is not toxic for E. coli at concentrations up to 300 mM and cellular preadaptation was crucial for the cells to grow. At concentrations between 300 mM and 450 mM, cells can tolerate this DES. Above 600 mM, the DES is toxic causing complete inhibition of growth. This toxicity is not only due to the chemical composition of the DES, but also due to the high acidification of the media caused by the DES hydrolysis during cellular growth. The consequences of sterilization procedures on the DES stability are also analysed into detail, finding that sterilization by autoclave promotes DES hydrolysis. From these results, new guidelines are proposed for furthers studies aiming to characterize and quantify DESs toxicity.