Ultra-rapid, enhanced and eco-friendly extraction of four main flavonoids from the seeds of Oroxylum indicum by deep eutectic solvents combined with tissue-smashing extraction

Optimization for ultrasound combined with flash extraction of polysaccharides from Phyllanthus emblica L. with antioxidant and hyperglycemic activity in vitro

Ultrasound-assisted flash extraction was used to rapidly extract polysaccharides from Phyllanthus emblica L. fruits (PEPs) with a good yield of 9.73 % ± 0.75 %. Furthermore, the PEPs were fractionated by graded precipitation of 30 %, 60 %, and 90 % (v/v) ethanol solution, and the respective molecular weight polysaccharide fractions, namely PEP-30 (166.88 kDa), PEP-60 (109.14 kDa), and PEP-90 (34.59 kDa) were obtained. The three fractions were composed of similar monosaccharides with galacturonic acid as the main constituent. The slope of R.M.S. radius-Mw curve showed that the three polysaccharide fractions were high-branched molecules with solid spherical conformation, and PEP-90 adopted a more compact conformation in aqueous solution. The three polysaccharide fractions had strong antioxidant activity, with PEP-60 showing the strongest antioxidant effect in vitro. PEP-30 (IC50 = 1.56 ± 0.14 mg/mL), PEP-60 (IC50 = 0.99 ± 0.09 mg/mL), and PEP-90 (IC50 = 0.63 ± 0.09 mg/mL) all exhibited mixed-type inhibition of α-glucosidase. Notably, PEP-90 showed the strongest inhibitory effect on α-glucosidase with the strongest binding ability to α-glucosidase and α-glucosidase-substrate complex, which are mainly related to different molecular weight. The results suggest the molecular weight of PEPs had great impact on their biological activities, providing important theoretical guiding for developing Phyllanthus emblica L. food products with the functional activity.

Successive extraction of key protein and polysaccharide from distillers' grains: Optimization, characterization, and economic analysis

Distillers' grains (DGS) are rich in various functional components and have received widespread attention from researchers for their extraction. However, current extraction methods typically isolate only a single component, which leads to low extraction efficiency and high processing costs. This study developed an integrated extraction strategy combining flash extraction with sequential enzymatic hydrolysis to obtain key proteins and polysaccharide components from DGS. Under optimized conditions, the method achieved recoveries of 92.70 %, 78.70 %, and 84.83 % for prolamin, polysaccharide, and gluten, with corresponding purities of 77.53 %, 95.96 %, and 84.81 %. Notably, the flash extraction significantly improved the recovery and purity of prolamin by 57.83 % and 49.54 %, respectively. FTIR spectroscopy comparisons revealed that prolamin exhibited lower solubility (17.19 %) and weaker emulsifying properties (EAI: 43.42 m2/g; ESI: 37.41 min), which were attributed to its high β-sheet content. Conversely, gluten demonstrated higher solubility (52.37 %) and superior emulsifying performance (EAI: 61.23 m2/g; ESI: 47.17 min) due to increased β-turn content. Moreover, the preliminary economic assessment of flash extraction and enzymatic hydrolysis for processing DGS showed a material cost of $952.29 per ton, yielding products with a total market value of $2793.94, indicating a profit margin approximately 2.93 times the material costs, highlighting the potential for industrial-scale implementation in sustainable biorefinery processes. This study successfully achieved the co-extraction of multiple components in DGS and provided a novel approach for the value-added utilization of DGS.

Green Extraction of Antioxidant-Rich Flavonoids from Fagonia cretica Using Deep Eutectic Solvents

This study optimized the extraction of flavonoids from Fagonia cretica using deep eutectic solvents (DESs), focusing on key factors such as the type of DES used, molar ratio, water content, solid/liquid ratio, extraction temperature, and time. Among six DESs tested, the betaine-acetic acid combination exhibited the highest extraction efficiency, attributed to its low viscosity (4.98 mPa·s). Optimal extraction conditions were determined to be a 1:4 molar ratio of betaine to acetic acid, a 25% water content, a solid/liquid ratio of 1:60 g/mL, an extraction temperature of 50 °C, and an extraction time of 30 min. Under these conditions, the flavonoid yield was maximized while preserving bioactivity. Antioxidant assays revealed that flavonoids extracted with DESs exhibited superior scavenging activity against DPPH and hydroxyl radical compared to ethanol-extracted flavonoids, highlighting DESs' potential to enhance antioxidant properties. The recyclability of DESs was demonstrated using ultracapacitor porous activated carbon, achieving an 89.78% recovery efficiency. The reused DES maintained a high flavonoid extraction yield, retaining 92% efficiency after six cycles, emphasizing its sustainability and cost-effectiveness. This study establishes DES-based extraction as an environmentally friendly and efficient approach for isolating flavonoids with strong antioxidant properties, offering significant advantages in green chemistry and bioactive compound recovery.

A review on the role of deep eutectic solvents in mango (Mangifera indica) extraction

The present review attempts to evaluate the applicability of deep eutectic solvents (DES) as a green technique for the extraction of phytochemicals from Mangifera indica L. and their therapeutic potential. Mango has been reported to show numerous therapeutic activities, which are attributed to its abundant source of bioactive compounds. Thus, the therapeutic potential of phytochemicals in mangoes is reviewed based on different reported bioactivity tests. The use of DESs is considered a green approach for the extraction of bioactive compounds from natural sources utilizing two or more components and a safe alternative for application in the nutritional, pharmaceutical and other sectors. The trends in the extraction of phytochemicals from mango using different DES components and different extraction parameters of the optimum protocol are reviewed. Hence, DESs are considered potential solvents with selective and efficient properties for extracting bioactive ingredients from mango. However, there are several knowledge gaps that need to be assessed for DES-based bioactive compound extraction from mango such as information on the local and specific varieties of mangoes, standardization of the extraction protocols and use of other parts of the mango plant as alternatives to its peel as bioactive sources. Accordingly, the extraction of bioactive compounds from mango using DESs will provide useful information for subsequent agricultural, pharmaceutical and nutraceutical applications in the future.

Optimization of Eco-Friendly Extraction of Bioactive Compounds from Mentha spicata L. Using Ultrasound-Assisted Extraction Combined with Choline Chloride-Based Deep Eutectic Solvents

Three choline chloride (ChCl)-based deep eutectic solvents (DESs) as a new type of green solvents were used for the ultrasound-assisted extraction (UAE) of bioactive compounds from Mentha spicata L. DES containing ChCl and malonic acid (MalA) was selected as the most promising, providing a more effective extraction of antioxidants from spearmint. Response surface methodology (RSM) and a Box-Behnken design (BBD) with three variables, ChCl:MalA molar ratio, water content (WC) in DES, and extraction time (t), were implemented for optimizing the extraction conditions. The optimal conditions were calculated to maximize the antioxidant capacity (AC) determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and cupric reducing antioxidant capacity (CUPRAC) assays, total phenolic acids (TPAc), total flavonoid aglycones (TFAgly), and total flavonoid glycosides (TFGly). The phenolic profiles in the obtained extracts were analyzed using ultra-performance liquid chromatography (UPLC), revealing that rosmarinic acid, ellagic acid, rutin, kaempferol, and kaempferol-3-O-rutinoside were predominant in the DES extracts.

Application of eco-friendly natural deep eutectic solvents (NADES) in HPLC for separation of complex natural products: Current limitations and future directions

Natural deep eutectic solvents (NADES) have been used in chromatography as extraction media and HPLC mobile phase additives, but only once have they been used as HPLC major mobile phase component. This review illustrates current knowledge and major limitations on use of NADES in HPLC mobile phase as well as to propose possible NADES may be ready for use as HPLC mobile phases and the detectors they can be used with. High viscosity is one of the major roadblocks encountered when using NADES as a mobile phase component in HPLC regardless of detectors employed. A comprehensive review of published literature was conducted to identify articles that focused on using NADES as extraction solvents for natural products, particularly polyphenols or reported NADES viscosities to establish a database of NADES which could be used as HPLC mobile phases under various conditions. Other identified challenges that limit NADES application in HPLC mobile phase include low volatility, NADES wavelength cutoff (UV and Fluorescent detectors) and impurities. Methods for overcoming these limitations are discussed so that NADES may be more integrated into HPLC systems in the future.

Ultrasound-Assisted Extraction of Phenolic Compounds from Celtuce (Lactuca sativa var. augustana) Leaves Using Natural Deep Eutectic Solvents (NADES): Process Optimization and Extraction Mechanism Research

Natural deep eutectic solvents (NADESs), as emerging green solvents, can efficiently extract natural products from natural resources. However, studies on the extraction of phenolic compounds from celtuce (Lactuca sativa var. augustana) leaves (CLs) by NADESs are still lacking. This study screened the NADES L-proline-lactic acid (Pr-LA), combined it with ultrasound-assisted extraction (UAE) to extract phenolic compounds from CLs, and conducted a comparative study on the extraction effect with traditional extraction solvents. Both SEM and FT-IR confirmed that Pr-LA can enhance the degree of fragmentation of cell structures and improve the extraction rate of phenolic compounds. Molecular dynamics simulation results show that Pr-LA can improve the solubility of phenolic compounds and has stronger hydrogen bonds and van der Waals interactions with phenolic compounds. Single-factor and Box-Behnken experiments optimized the process parameters for the extraction of phenolic compounds from CLs. The second-order kinetic model describes the extraction process of phenolic compounds from CLs under optimal process parameters and provides theoretical guidance for actual industrial production. This study not only provides an efficient and green method for extracting phenolic compounds from CLs but also clarifies the mechanism of improved extraction efficiency, which provides a basis for research on the NADES extraction mechanism.

Density-oriented deep eutectic solvent-based system for the selective separation of polysaccharides from Astragalus membranaceus var. Mongholicus under ultrasound-assisted conditions

The water extraction and ethanol precipitation method is an extraction method based on the solubility characteristics of polysaccharides that offers wide applicability in the extraction and separation of plant polysaccharides. However, this method leads to large amounts of proteins, nucleic acids, pigments, and other impurities in the polysaccharides products, which makes downstream purification complicated and time-consuming. In this study, a green, high-density natural deep eutectic solvents was used for the high-purity extraction and separation of polysaccharides from Astragalus membranaceus (Fisch) Bge. var. Mongholicus (Bge.) Hsiao roots under ultrasound-assisted conditions. In this study, 16 different natural deep eutectic solvents were designed to screen the best solvent for extracting Astragalus polysaccharides (APSs). Based on the yield and recovery of APSs, a natural deep eutectic solvents composed of choline chloride and oxalic acid with a molar ratio of 1:2 was selected. The related factors affecting polysaccharides extraction and solvent precipitation were investigated. To improve the operating methodology, single-factor trials, a Plackett-Burman design, and a Box-Behnken design were used. The optimal extraction process conditions were obtained as follows: water content of 55%, liquid-solid ratio of 24 mL/g, ultrasonic irradiation time of 54 min, ultrasonic irradiation temperature of 50 °C, ultrasonic irradiation power of 480 W, ethanol precipitation time of 24 h, and ethanol concentration of 75%. Under optimal extraction conditions, the recovery of APSs was 61.4 ± 0.6 mg/g. Considering the special matrix characteristics of A. membranaceus var. Mongholicus roots, physical-technology-based ultrasonic waves promote penetration, and the mass transfer function also solves the bottleneck of high-viscosity deep eutectic solvents in the extraction stage. In comparison with the conventional method, the proposed method based on deep eutectic solvents isolation can significantly increase APSs recovery, which is beneficial to simplifying the process of polysaccharides purification by using solvent properties to separate extracts and reduce impurities in APSs.

Deep Eutectic Solvents-Based Ultrasound-Assisted Extraction of Antioxidants from Kudingcha (llex kudingcha C.J. Tseng): Process Optimization and Comparison with Other Methods

Kudingcha (KDC) is an important tea substitute containing abundant antioxidants. Herein, a ultrasonic-assisted extraction (UAE) technique based on deep eutectic solvents (DESs) was applied to optimize the total phenolic/total flavonoid content (TPC/TFC) from the KDC extracts. Results indicated that DES composed of L-proline and glycerol (Pro-Gly) had excellent extraction performance for TPC, TFC, ABTS•+ and FRAP, which were significantly better than other solvents. Response surface methodology (RSM) was used to obtain optimal extraction parameters for simultaneously maximizing the TPC, TFC and antioxidant activity. Results revealed that water content in Pro-Gly, liquid to solid ratio (L/S), ultrasonic temperature and extraction time were the major influence factors of the TPC, TFC, ABTS•+ and FRAP of the KDC extracts. The optimal conditions included water content in Pro-Gly of 46.4%, L/S of 25:1 (mL/g), ultrasonic temperature of 55 °C and extraction time of 50 min. Meanwhile, HPLC-MS/MS was adopted to identify the KDC extracts, which revealed the presence of major phytochemicals, including 5-chlorogenic acid, 4,5-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, 3,4-dicaffeoylquinic acid, kaempferol 3-rutinoside, myricetin and isorhamnetin. Moreover, UAE-Pro-Gly achieved further higher individual phenolics contents, TPC, TFC, ABTS•+ and FRAP than other methods. In conclusion, UAE-Pro-Gly is a highly efficient method for extraction of phenolic antioxidants from KDC.

Microwave-ultrasonic technique development coupled with natural deep eutectic solvents in anthocyanin extraction from perilla leaves (Perilla frutescens var. Acuta)

BACKGROUND

As potent antioxidants, anthocyanins can protect the body from free radicals. However, the traditional solvent extraction method has the disadvantages of requiring a high extraction temperature and long extraction time, so it is necessary to develop an efficient extraction method for anthocyanins.

RESULTS

In this study, the technique of natural deep eutectic solvents (DESs) was applied to extract anthocyanins from purple perilla leaves with the aid of microwave-ultrasonic assisted extraction (MUAE). The response surface methodology (RSM), based on the Box-Behnken design (BBD), predicted the maximum extraction yield of anthocyanins to be 619.62 mg (100 g)^-1 under the following conditions: x₁ (ultrasonic extraction power) = 357.25 W, x₂ (time) = 25.62 min, and x₃ (temperature) = 57.80 °C. The biological activity of the extract obtained was evaluated by examining its radical-scavenging effect on 1,1-diphenyl-2-picrylhydrazyl, hydroxyl radical, and superoxide anion radicals. Its bacteriostatic impact was investigated on four typical bacteria: Shewanella putrefaciens (S. putrefaciens), Pseudomonas fluorescens (P. fluorescens), Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus).

CONCLUSION

The integrated extraction method of DESs with MUAE was efficient, energy-saving, green, and sustainable. © 2022 Society of Chemical Industry.

Updating the status quo on the extraction of bioactive compounds in agro-products using a two-pot multivariate design. A comprehensive review

Extraction is regarded as the most crucial stage in analyzing bioactive compounds. Nonetheless, due to the intricacy of the matrix, numerous aspects must be optimized during the extraction of bioactive components. Although one variable at a time (OVAT) is mainly used, this is time-consuming and laborious. As a result, using an experimental design in the optimization process is beneficial with few experiments and low costs. This article critically reviewed two-pot multivariate techniques employed in extracting bioactive compounds in food in the last decade. First, a comparison of the parametric screening methods (factorial design, Taguchi, and Plackett-Burman design) was delved into, and its advantages and limitations in helping to select the critical extraction parameters were discussed. This was followed by a discussion of the response surface methodologies (central composite (CCD), Doehlert (DD), orthogonal array (OAD), mixture, D-optimal, and Box-Behnken designs (BBD), etc.), which are used to optimize the most critical variables in the extraction of bioactive compounds in food, providing a sequential comprehension of the linear and complex interactions and multiple responses and robustness tests. Next, the benefits, drawbacks, and possibilities of various response surface methodologies (RSM) and some of their usages were discussed, with food chemistry, analysis, and processing from the literature. Finally, extraction of food bioactive compounds using RSM was compared to artificial neural network modeling with their drawbacks discussed. We recommended that future experiments could compare these designs (BBD vs. CCD vs. DD, etc.) in the extraction of food-bioactive compounds. Besides, more research should be done comparing response surface methodologies and artificial neural networks regarding their practicality and limitations in extracting food-bioactive compounds.

Deep Eutectic Solvent-Based Ultrasound-Assisted Strategy for Simultaneous Extraction of Five Macamides from Lepidium meyenii Walp and In Vitro Bioactivities

This study aimed to develop an integrated approach of deep eutectic solvent-based ultrasound-assisted extraction (DES-UAE) to simultaneously extract five major bioactive macamides from the roots of Lepidium meyenii Walp. Ten different DESs containing choline chloride and selected hydrogen-bond donors were prepared and evaluated based on the extracted macamide content determination using high-performance liquid chromatography (HPLC). Choline chloride/1,6-hexanediol in a 1:2 molar ratio with 20% water exhibited the most promising extraction efficiencies under the optimized parameters verified using single-factor optimization as well as Box-Behnken design. Using the optimized DES-UAE method, the extraction efficiencies of the five macamides were up to 40.3% higher compared to those using the most favorable organic solvent petroleum ether and were also superior to those of the other extraction methods, such as heating and combination of heating and stirring. Furthermore, using the macroporous resin HPD-100, the recoveries of the five target macamides from the DES extraction reached 85.62-92.25%. The 20 μg/mL group of the five macamide extracts showed superior neuroprotective activity against PC12 cell injury than that of the positive drug nimodipine. The macamide extracts also showed higher NO inhibition in LPS-stimulated RAW264.7 cells. Thus, the developed approach was a green and potential alternative that can be used to extract bioactive macamide constituents from L. meyenii in the pharmaceutical and food industries.

Utilization of natural deep eutectic solvents and ultrasound-assisted extraction as green extraction technique for the recovery of bioactive compounds from date palm (Phoenix dactylifera L.) seeds: An investigation into optimization of process parameters

The green extraction of bioactive compounds from date seeds was investigated using seven natural deep eutectic solvents (NADES) coupled with ultrasound-assisted extraction (UAE). The seven NADESs mainly consisted of choline chloride as hydrogen bond acceptors (HBA) and four sugars, two organic acids, and one polyalcohol as hydrogen bond donors (HBD) were utilized in this study. When the extraction efficiency of the NADESs was compared to that of the conventional solvents, all the NADESs showed superior bioactive compounds recovery efficacy. The lactic acid-based NADES had the highest extraction efficiency and was further optimized using the response surface method and Box-Behnken design. A four-factors including extraction time (10, 20, and 30 min), ultrasound amplitude (70, 80, and 90 %), % NADES content (30 %, 50 %, and 70 %) and solid-to-solvent ratio (1:30, 1.5:30, and 2:30 g/ml) each at three levels (-1, 0 and 1) using Box-Behnken design was applied. The % NADES content and the solid-to-solvent ratio were the major factors influencing the extraction efficiency of the total phenolic content (TPC) and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. The optimum extraction conditions included an extraction time of 15 min, ultrasound amplitude of 90 %, % NADES content of 70 % and solid-to-liquid ratio of 1:30 g/ml. The experimental values for TPC and DPPH at optimum extraction conditions were 145.54 ± 1.54 (mg GAE/g powder) and 719.19 ± 2.09 (mmol TE/g powder), respectively. The major phenolic compounds observed in the date seeds extracted using ChCl-LA were 3,4-dihydroxybenzoic acid, catechin and caffeic acid. This study reveals that the extraction of date seeds with NADES in combination with UAE technique was able to recover significantly higher amounts of phenolic compounds which could find useful applications in the food, pharmaceutical, and cosmetics industries.

The Influence of Different Extraction Techniques on the Chemical Profile and Biological Properties of Oroxylum indicum: Multifunctional Aspects for Potential Pharmaceutical Applications

Oroxylum indicum (L.) Kurz (Bignoniaceae), a traditional Chinese herbal medicine, possesses various biological activities including antioxidant, anti-inflammatory, antibacterial, and anticancer. In order to guide the practical application of O. indicum in the pharmaceutical, food, and cosmetic industries, we evaluated the effects of five different extraction techniques (maceration extraction (ME), oxhlet extraction (SOXE), ultrasound-assisted extraction (UAE), tissue-smashing extraction (TSE), and accelerated-solvent extraction (ASE)) with 70% ethanol as the solvent on the phytochemical properties and biological potential. The UHPLC-DAD Orbitrap Elite MS technique was applied to characterize the main flavonoids in the extracts. Simultaneously, the antioxidant and enzyme inhibitory activities of the tested extracts were analyzed. SOXE extract showed the highest total phenolic content (TPC, 50.99 ± 1.78 mg GAE/g extract), while ASE extract displayed the highest total flavonoid content (TFC, 34.92 ± 0.38 mg RE/g extract), which displayed significant correlation with antioxidant activity. The extract obtained using UAE was the most potent inhibitor of tyrosinase (IC50: 16.57 ± 0.53 mg·mL-1), while SOXE extract showed the highest activity against α-glucosidase (IC50: 1.23 ± 0.09 mg·mL-1), succeeded by UAE, ME, ASE, and TSE extract. In addition, multivariate analysis suggested that different extraction techniques could significantly affect the phytochemical properties and biological activities of O. indicum. To sum up, O. indicum displayed expected biological potential and the data collected in this study could provide an experimental basis for further investigation in practical applications.

Effects of five extraction methods on total content, composition, and stability of flavonoids in jujube

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Five methods of extracting flavonoids from jujube were compared in different aspects.

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The extraction methods can significantly influence the flavonoid compositions.

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DES-UAE method had outstanding ability to maintain the stability of flavonoids.

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DES-UAE is an efficient and green method for extracting flavonoids from jujube.

The present study investigated the effects of different extraction methods including water-water bath (W-WB), ethanol-water bath (E-WB), deep eutectic solvent (DES) combined with ultrasound-assisted extraction (DES-UAE), microwave-assisted extraction (DES-MAE), and enzyme-assisted extraction (DES-EAE) on flavonoids (total flavonoid content, flavonoid composition, and stability) in jujube. The highest total flavonoid content of 8.03 mg/g was obtained by the DES-MAE extraction. Fifteen types of flavonoids were identified from jujube. The amount of rutin produced by the E-WB and DES-UAE methods was 66.88 ± 1.58 μg/g and 45.23 ± 3.22 μg/g, respectively. The retention of flavonoids in DES-UAE extracts were 98.15 ± 0.51%, 64.25 ± 2.21% after 2 h of high temperature treatment at 90 °C and 21 days of dark storage, respectively. The flavonoids extracted by different methods were suitable for dark storage under different light contrasts, where the retention of flavonoids extracted by DES-UAE method was 86.44 ± 2.45%. In conclusion, DES-UAE would be an efficient method for flavonoid extraction from jujube.

Extraction of Bioactive Metabolites from Achillea millefolium L. with Choline Chloride Based Natural Deep Eutectic Solvents: A Study of the Antioxidant and Antimicrobial Activity

In this study, the extraction efficiency of natural deep eutectic solvents (NADES) based on choline chloride as a hydrogen bond acceptor (HBA) and five different hydrogen bond donors (HBD; lactic acid, 1,4-butanediol, 1,2-propanediol, fructose and urea) was evaluated for the first time for the isolation of valuable bioactive compounds from Achillea millefolium L. The phytochemical profiles of NADES extracts obtained after ultrasound-assisted extraction were evaluated both spectrophotometrically (total phenolic content (TPC) and antioxidant assays) and chromatographically (UHPLC-MS and HPLC-UV). The results were compared with those obtained with 80% ethanol, 80% methanol, and water. The highest TPC value was found in the lactic acid-based NADES (ChCl-LA), which correlated with the highest antioxidant activity determined by the FRAP analysis. On the other hand, the highest antiradical potential against ABTS+• was determined for urea-based NADES. Phenolic acids (chlorogenic acid and dicaffeoylquinic acid isomers), flavones (luteolin and apigenin), and their corresponding glucosides were determined as the dominant individual phenolic compounds in all extracts. The antibacterial and antifungal properties of the extracts obtained against four bacterial cultures and two yeasts were evaluated using two methods: the agar dilution method to obtain the minimum inhibitory concentration (MIC) and the minimum bactericidal or fungicidal concentration (MBC or MFC), and the disc diffusion method. ChCl-LA had the lowest MIC and MBC/MFC with respect to all microorganisms, with an MIC ranging from 0.05 mg mL−1 to 0.8 mg mL−1, while the water extract had the weakest inhibitory activity with MIC and MBC/MFC higher than 3.2 mg mL−1.

Amaranth Seed Polyphenol, Fatty Acid and Amino Acid Profile

In this paper, the extraction of polyphenols from amaranth seed using a Box–Benhken design using four factors—ultra-turrax speed, solid-to-liquid ratio (RSL), methanol concentration and extraction time—were studied. There were two responses studied for the model: total phenolic content (TPC) and total flavonoid content (TFC). The factors which influenced the most the extraction of the TPC and TFC were the RSL, methanol concentration and ultra-turrax speed. Twelve phenolic acids (rosmarinic acid, p-coumaric acid, chlorogenic acid, vanillic acid, caffeic acid, p-hydroxybenzoic acid, protocatechuic acid and gallic acid) and flavonoids (kaempferol, quercetin, luteolin and myricetin) were studied, and the most abundant one was kaempferol followed by myricetin. The amaranth seed is a valuable source of fatty acids, and 16.54% of the total fatty acids determined were saturated fatty acids, while 83.45% of the fatty acids were unsaturated ones. Amaranth seed is a valuable source of amino acids, with 9 essential amino acids being reported: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

Application of Extraction and Determination Based on Deep Eutectic Solvents in Different Types of Environmental Samples

Water sources are an indispensable resource for human survival. Monitoring the pollution status of the surrounding environment is necessary to protect water sources. Research on the environmental matrix of deep eutectic solvents (DESs) has expanded rapidly because of their high extraction efficiency for various target analytes, controllable synthesis, and versatile structure. Following the synthesis of hydrophobic deep eutectic solvents (HDESs), their application in aqueous matrices broadened greatly. The present review conducted a survey on the pollutant extraction methods based DESs in environmental matrices from two aspects, application methods and matrix types; discussed the potential risk of DESs to the environment and future development trends; and provided some references for researchers to choose DES-based extraction methods for environmental research.

Study on enhanced extraction and seasonal variation of secondary metabolites in Eucommia ulmoides leaves using deep eutectic solvents

It has been considered as a crucial field for the extraction of active ingredients from herbal medicine to use a green and efficient method in the medicinal and food industries. In recent years, deep eutectic solvents (DESs) have been obtaining increase attention in green chemistry area since its sustainability, safety and biodegradability. In this study, an efficient DES composed of choline chloride and L-(+)-ascorbic acid with a molar ratio of 2:1 performed higher efficacy on the extraction of target compounds (including iridoids, phenolic acids and flavonoids) in Eucommia ulmoides leaves than 50% methanol solution. Considering the extraction efficacy and time consumption, microwave-assisted extraction (MAE) was selected and the operational conditions, including power of microwave, liquid/solid ratio and irradiation time were optimized by response surface methodology (RSM). Water was used as anti-solvent to recover ten target analytes from DES with recovery yields of 97.59%, 94.91%, 96.09%, 90.66%, 95.16%, 87.33%, 86.57%, 82.15%, 89.28% and 80.75% for eucommiol (EU), aucubin (AU), geniposidic acid (GA), chlorogenic acid (CA), asperuloside (AP), rutin (RU), kaempferol-3-O-sambubioside (KS), isoquercitrin (IQ), kaempferol-3-O-rutinoside (KR) and astragaline (AS), respectively. By combining the DES-based MAE and quantitative analysis of multi-components by single mark (QAMS) methods, the contents of ten compounds in the leaves of Eucommia ulmoides were determined to clarify the relationship between the accumulation of secondary metabolites and the harvest period. It was found that the contents of main ingredients reached the highest during May to October. The period appears to be the best harvest period for Eucommia ulmoides leaves. This study provides a novel strategy for the harvesting, processing, and quality control of the raw materials from Eucommia ulmoides leaves.

Vortex-assisted natural deep eutectic solvent dispersive liquid-liquid microextraction based on the solidification of a floating organic drop for the determination of benzoic acid and sorbic acid in condiments

A simple, inexpensive, reliable and environmentally friendly method based on vortex-assisted dispersive liquid-liquid microextraction combined with solidification of a floating organic drop (VA-DLLME-SFO) followed by high performance liquid chromatography with a diode array detector (HPLC-DAD) was developed to determine benzoic acid (BA) and sorbic acid (SA) in ketchup and powder bags of instant noodles. Hydrophobic natural deep eutectic solvents (NADESs), as the microextraction solvent, were prepared with ternary components. Acetic acid can reduce the viscosity of hydrophobic NADESs and vortex can promote the dispersion of NADESs in aqueous solvents. In the DLLME process, several key parameters were optimized, including the type and volume of hydrophobic NADES, pH value, vortex time and salt content. Meanwhile, these parameters were assessed using response surface methodology based on the Box-Behnken design (BBD). Under optimal conditions, the developed method showed good linearity in the selected range (r², 0.9997). The limits of detection were 0.2 μg mL^-1 and 0.07 μg mL^-1 for BA and SA, respectively. Recoveries were in the range of 82.21% to 102.70% and the relative standard deviations (intra-day and inter-day precisions) were less than 5.66%. The proposed method was successful in analyzing BA and SA in ketchup and powder bags of instant noodles.

Purification of linarin and hesperidin from Mentha haplocalyx by aqueous two-phase flotation coupled with preparative HPLC and evaluation of the neuroprotective effect of linarin

The volatile oil of Mentha haplocalyx is widely used in medicine, food, and cosmetics. However, a large amount of its residue after steam extraction of volatile oil is abandoned, resulting in a waste of resources. The method of aqueous two-phase flotation coupled with preparative high-performance liquid chromatography was established for the separation and purification of nonvolatile active compounds from Mentha haplocalyx for the first time. The parameters of the two-phase aqueous flotation were optimized. Under the optimal conditions including flotation solvent PEG 1000 aqueous solution (1:1, w/w), pH 5, (NH₄ )₂ SO₄ concentration of 350 g/L in aqueous phase, N₂ flow rate of 20 mL/min, and flotation time of 20 min, the flotation efficiency of linarin, hesperidin, and didymin was 82.24, 76.38, and 89.33%, respectively. The linarin and hesperidin with the high purities of 95.8 and 97.2%, respectively, were obtained by using preparative high performance liquid chromatography. The neuroprotective effect of linarin against H₂ O₂ -induced oxidative stress in rat hippocampal neurons was investigated. The experimental result indicated that linarin could alleviate H₂ O₂ -induced oxidative stress. The work indicated that the combination of aqueous two-phase flotation and preparative high performance liquid chromatography is a feasible and practical method for the purification of nonvolatile active substances from Mentha haplocalyx, which would provide a reference process for the comprehensive utilization of M. haplocalyx. Especially, linarin might be used as a good source of natural neuroprotectants.

Optimized ultrasound-assisted extraction of total polyphenols from Empetrum nigrum and its bioactivities

Optimization of ultrasound-assisted extraction (UAE) of total polyphenols (TPP) from Empetrum nigrum aerial parts was carried out by response surface methodology (RSM). The optimum UAE conditions of extraction time, extraction temperature, ethanol concentration, and solvent-to-material ratio were 21.38 min, 42.32 °C, 61.93% and 53.29:1 mL/g, respectively. Under the optimum conditions, the extraction yield of TPP was 32.17 ± 0.46 mg/g, which was 1.29-1.44 folds to those by the conventional extraction methods. In addition, the bioactivities of the extracts were investigated. Antioxidant activity test by the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay revealed that the TPP extracts had a high potential for free radical scavenging activity. The TPP extracts showed remarkable antibacterial activity against both Gram-positive and Gram-negative strains, especially against Gram-positive strains. The evaluation of antitumor activity by the MTT assay and flow cytometric analysis indicated that the TPP extracts significantly inhibited B 16F 10 melanoma cell proliferation and effectively induced apoptosis of melanoma cells. These results demonstrate that E. nigrum aerial parts are rich in TPP and show great application potential in the pharmaceutical industry.

Extraction and separation of flavonoids from Malus hupehensis using high-speed countercurrent chromatography based on deep eutectic solvent

In the present experiment, a green and highly efficient extraction method for flavonoids established on deep eutectic solvents (DESs) was investigated by using the response surface methodology. The DES-based high-speed countercurrent chromatography (HSCCC) solvent systems were developed for the separation of high purity compounds from the DES extract of Malus hupehensis for the first time. Under the optimal conditions (liquid-to-solid ratio of 26.3 mL/g, water content of 25.5%, and extraction temperature of 77.5°C), the yield of flavonoids was 15.3 ± 0.1%, which was superior to that of the methanol extraction method. In accordance with the physical property of DES-based HSCCC solvent systems and K values of target compounds, DES-based HSCCC solvent systems composed of choline chloride/glucose-water-ethyl acetate (ChCl/Glu-H₂O-EAC, 1:1:2, v/v) was selected for the HSCCC separation. Thus, five flavonoids (two novel compounds 1-2, 6´´-O-coumaroyl-2´-O-glucopyranosylphloretin and 3´´´-methoxy-6´´-O-feruloy-2´-O-glucopyranosylphloretin; three know compounds 3-5, namely, avicularin, phloridzin, and sieboldin) were efficiently separated from Malus hupehensis. DESs are the environment friendly and highly efficient solvents as the components of extraction solvent and HSCCC solvent system, and can be re-utilized many times. However, ethyl acetate can be soluble with a few hydrogen bond donors, such as urea, carboxylic acid and polyol, through the shake flask test. It is the great difficulty for the efficient and rapid separation of target compounds from the DESs extract because of the DESs residual in the HSCCC fractions. ChCl and Glu are the great choices of DESs without this problem. In addition, K values increased with the increase of the molar ratio of ChCl/Glu and the content of water, which could effectively guide us to choose the suitable DES-based HSCCC solvent system. The twice HSCCC separation results indicated that DES was the valuable and green solvent for the HSCCC separation of pure compounds from the extract for the first time, and showed the recycle superiority of DES-based HSCCC solvent system.

Review on Extraction of Phenolic Compounds from Natural Sources Using Green Deep Eutectic Solvents

For more sustainable and environmentally friendly scientific research, it is essential to apply green chemistry principles in all areas of science. A possible area in which green chemistry principles can significantly influence the productivity and the quality of the outcome is extraction of natural products. The conventional toxic solvents can be replaced by environmentally friendly solvents known as deep eutectic solvents, which fortunately, due to their unique properties, can significantly improve extraction efficiency. In this literature review, the extraction of a specific class of natural products, phenolic compounds, using different types of green deep eutectic solvents has been reviewed. Within this review, the composition of those solvents used to extract different types of phenolic compounds has been discussed. In addition, the factors affecting their extraction, extracting solvent component structure, molar ratio of extracting solvent components, extraction temperature, solid to extraction solvent ratio, and water content, have been evaluated.

Innovative Extraction Techniques Using Deep Eutectic Solvents and Analytical Methods for the Isolation and Characterization of Natural Bioactive Compounds from Plant Material

The growing interest of the food, pharmaceutical and cosmetics industries in naturally occurring bioactive compounds or secondary plant metabolites also leads to a growing demand for the development of new and more effective analysis and isolation techniques. The extraction of bioactive compounds from plant material has always been a challenge, accompanied by increasingly strict control requirements for the final products and a growing interest in environmental protection. However, great efforts have been made in this direction and today a considerable number of innovative extraction techniques have been developed using green, environmentally friendly solvents. These solvents include the deep eutectic solvents (DES) and their natural equivalents, the natural deep eutectic solvents (NADES). Due to their adjustable physical-chemical properties and their green character, it is expected that DES/NADES could be the most widely used solvents in the future, not only in extraction processes but also in other research areas such as catalysis, electrochemistry or organic synthesis. Consequently, this review provided an up-to-date systematic overview of the use of DES/NADES in combination with innovative extraction techniques for the isolation of bioactive compounds from various plant materials. The topicality of the field was confirmed by a detailed search on the platform WoS (Web of Science), which resulted in more than 100 original research papers on DES/NADES for bioactive compounds in the last three years. Besides the isolation of bioactive compounds from plants, different analytical methods are presented and discussed.