Optimizing the ultrasound-assisted deep eutectic solvent extraction of flavonoids in common buckwheat sprouts

Valorization of waste tomato leaves with natural deep eutectic solvents

Waste produced during cultivation of edible plants can be a valuable source of bioactive molecules. Herein, we present the valorization of tomato leaves to obtain biologically active extracts. Deep eutectic solvents (DESs), composed of natural ingredients, were applied as extracting solvents. The extracts were rich in bioactive chemicals such as phenolics and flavonoids, with rutin as the main component (∼6 mg/g of biomass). The obtained extracts showed high antioxidative potential. Moreover, it was possible to recycle DES for subsequent extractions. Evaluation of the antimicrobial activity of the extracts against selected bacteria (Escherichia coli and Staphylococcus epidermidis) and yeast (Candida albicans) revealed that it showed strong antifungal activity, while the pure solvent did not exhibit such properties. The study revealed that by adhering to the principles of the circular economy and extracting waste tomato leaves using natural DESs, valuable antioxidants and antimicrobial agents can be obtained with high yields.

Current developments and trends in hybrid extraction techniques for green analytical applications in natural products

Natural product extraction has advanced significantly due to the growing need for environmentally friendly and sustainable analytical techniques. The medicinal benefits of natural products are gaining worldwide recognition. This shift emphasizes the need for sustainable extraction methods, as traditional organic solvents can negatively impact biodiversity. This review looks at new green extraction methods such as pressurized liquid extraction, ultrasound-assisted extraction, microwave-assisted extraction, and supercritical fluid extraction. The overview describes the main goals, workings, and extraction principles of these techniques, which are used to extract phytochemicals from various plant sources. Additionally covered is how green solvents, more especially bio-based and deep eutectic solvents, can enhance the sustainability of these techniques. This review examines the developments in synergistic extraction, emphasizing how these hybrid techniques can be used to isolate a variety of natural products, including polyphenols, alkaloids, essential oils, and more. It also emphasizes how crucial these techniques are to the development of high-performance, environmentally friendly analytical platforms for the use of natural products. The recent uses of these extraction techniques are covered in this review. Despite the positive results, standardization, selectivity, scalability, and economic viability issues must be recognized and addressed.

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.

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.

Deep eutectic system enhanced oat protein extraction

Oats are a rich source of plant-based proteins owing to their nutritional value, diverse functions, and high abundance. However, traditional methods for extracting oat proteins (OPs), such as alkali solution acid precipitation (ASAP), can cause environmental pollution and potentially protein denaturation. In this work, we studied the use of deep eutectic solvents (DESs) and deep eutectic system (DESys)-based methods for OP extraction. The DES are composed of ionic liquids (ILs) and choline chloride (ChCl) as hydrogen bond acceptors (HBAs), and polyols as hydrogen bond donors (HBDs) for OP extraction. By systematically investigating the extraction conditions, it was found that using ChCl as an HBA in the DESys-based method allowed for a significant increase in protein recovery yield compared to the ASAP and DES-based methods. Furthermore, the physicochemical properties of OPs extracted using the ASAP, DES, and DESys-based methods exhibited some differences, particularly in their molecular structure, amino acid composition, and thermal properties, suggesting that the properties of OP could be potentially adjusted by DESys- and DES-based methods. When considering both toxicity and protein recovery yield, the DESys-based extraction method using ChCl as the HBA is more suitable for OP extraction. This study demonstrated a green and efficient method for OP extraction that minimizes environmental impact, potentially bridging the gap between ILs and DES, and offering insights for designing new DES- or DESys-based extraction strategies for biological molecules.

A comparative study on sequential green hybrid techniques (ultrasonication, microwave and high shear homogenization) for the extraction of date seed bioactive compounds and its application as an additive for shelf-life extension of Oreochromis niloticus

This study focuses on the extraction of bioactive compounds from date seeds using five polyol-based deep eutectic solvents (P-DESs) in combination with hybrid green extraction techniques, specifically microwave-assisted extraction (MAE), homogenization-assisted extraction (HAE), and ultrasound-assisted extraction (UAE). The optimization of these extraction techniques was achieved using P-DESs showing the highest efficiency for extracting date seed bioactive compounds using response surface methodology (RSM) and central composite design (CCD) approach. The optimized conditions from three green techniques were further applied in the form of hybrid green extraction techniques, involving six binary and three ternary methods, to assess the percentage increase in the extraction efficiency of date seed bioactive polyphenolics. Among the five P-DESs tested, choline chloride: ethylene glycol (ChCl:Eg) exhibited the highest extraction efficiency for recovering date seed phenolic compounds. Using ChCl:Eg as the P-DES, the highest extraction efficacy was found with MAE, followed by > HAE and > UAE. In addition, all hybrid extraction techniques showed higher extraction efficiencies than the single extraction methods. Notably, the binary hybrid techniques combining UAE and MAE (UMAE), HAE and MAE (HMAE) resulted in significantly higher recovery of bioactive compounds, with 52 % and 49 % increases in total phenolic content, respectively, compared to single extraction techniques. The lowest MIC and MBC of P-DES (ChCl:Eg) and date seed P-DES based extract recorded against all the tested bacterial strains was 40 % and 20 % respectively. Furthermore, the date seed extract from MAE was used to extend the shelf life of Oreochromis niloticus stored at 4 °C for 10 days. The results indicated that the date seed polyphenolic extract effectively inhibited microbial growth in Oreochromis niloticus during refrigerated storage, with the total bacterial count (TBC) of all the treated samples within the recommended acceptability limit of < 6 log CFU/g compared to the untreated samples, which showed a total bacterial count (TBC) > 6 log CFU/g. This study demonstrated that sequential hybrid techniques enhance and intensify the recovery of bioactive compounds more effectively than any single green technique.

Turning Waste into Wealth: Optimization of Microwave/Ultrasound-Assisted Extraction for Maximum Recovery of Quercetin and Total Flavonoids from Red Onion (Allium cepa L.) Skin Waste

This study optimized the extraction conditions to maximize the recovery yields of quercetin and total flavonoids from red onion skin waste using sequential microwave/ultrasound-assisted extraction. Five effective factors of quercetin extraction yield were investigated using response surface methodology. The method was successfully performed under optimal 60 s microwave irradiation conditions followed by 15 min sonication at 70 °C with 70% (v/v, water) ethanol with a solvent-to-solid ratio of 30 mL/g. The variance analysis of the model for both quercetin (Y1) and total flavonoid (Y2) recovery from DOS demonstrated that ultrasound temperature (X2) was the most highly significant and influential factor, with a p-value of <0.0001 for both responses. Additionally, three key interaction terms—X1X2, X2X4, and X2X5—were identified as highly significant, further underscoring the critical role of ultrasound temperature in optimizing the extraction process for both quercetin and total flavonoids. The maximum recovery yields of quercetin and total flavonoids from red onion skin were 10.32% and 12.52%, respectively. The predicted values for quercetin (10.05%) and total flavonoids (12.72%) were very close to the experimental results. The recovery yields obtained from different extraction methods under the identical experimental conditions mentioned earlier were ultrasound/microwave-assisted extraction (7.66% quercetin and 10.18% total flavonoids), ultrasound-assisted extraction (5.36% quercetin and 8.34% total flavonoids), and microwave-assisted extraction (5.03% quercetin and 7.91% total flavonoids). The ANOVA confirmed highly significant regression models (p-values < 0.0001), with an insignificant lack of fit (p = 0.0515 for quercetin, p = 0.1276 for total flavonoids), demonstrating the robustness and reliability of the optimization. This study provides valuable insights for improving the extraction of bioactive compounds, which is critical for developing effective cancer treatments and advancing medical research. Additionally, the model shows potential for scaling up food processing applications to recover valuable products from red onion skin waste.

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.

Deep eutectic solvents for the extraction of polyphenols from food plants

Deep Eutectic Solvents (DESs) offer a promising, sustainable alternative for extracting polyphenols from food plants, known for their health benefits. Traditional extraction methods are often costly and involve toxic solvents. This review discusses the basic concepts, preparation techniques, and factors influencing the effective and safe use of DESs in polyphenol extraction. DESs' adaptability allows integration with other green extraction technologies, such as microwave- and ultrasound-assisted extractions, enhancing their efficiency. This adaptability demonstrates the potential of DESs in the sustainable extraction of bioactive compounds. Current research indicates that DESs could play a significant role in the sustainable procurement of these compounds, marking an important advancement in food science research and development. The review underscores DESs as a realistic, eco-friendly alternative in the realm of natural extraction technologies, offering a significant contribution to sustainable practices in food science.

Deep eutectic solvents: Preparation, properties, and food applications

Deep Eutectic Solvents (DESs) emerge as innovative 21st-century solvents, supplanting traditional ones like ethanol and n-hexane. Renowned for their non-toxic, biodegradable, and water-miscible nature with reduced volatility, DESs are mostly synthesized through heating and stirring method. Physicochemical properties such as polarity, viscosity, density and surface tension of DESs influenced their application. This review paper gives the overview of application of eco-benign DESs in fruits, vegetables, cereals, pulses, spices, herbs, plantation crops, oil seed crops, medicinal and aromatic plants, seaweed, and milk for the extraction of bioactive compounds. Also, it gives insight of determination of pesticides, insecticides, hazardous and toxic compounds, removal of heavy metals, detection of illegal milk additive, purification of antibiotics and preparation of packaging film. Methodologies for separating bioactive compounds from DESs extracts are systematically examined. Further, safety regulations of DESs are briefly discussed and reviewed literature reveals prevalent utilization of DES-based bioactive compound rich extracts in cosmetics, indicating untapped potential of their application in the food industry.

Bioactive compound composition and cellular antioxidant activity of fig (Ficus carica L.)

BACKGROUND

Fig (Ficus carica L.) fruit is consumed worldwide as a functional food. It contains phytochemicals that have been related to health benefits. However, the characteristic chemicals remain unclear. In this work, phytochemicals were prepared from figus by ultrasound-assisted extraction under optimized conditions. The chemical composition of fig fruit and leaves was characterized by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).

RESULTS

One hundred and fifty-seven compounds were identified, including 58 flavonoids, 29 coumarins, 19 acids, 15 terpenoids, 11 alkaloids, and 25 other compounds. The mass spectrum (MS) fragmentation pathways of representative chemicals were elucidated. Flavonoid glycosides and prenylated flavonoids were mainly present in fig fruit, whereas coumarins were abundant in leaves. Both fig fruit and leaf extracts showed good cellular antioxidant activity.

CONCLUSION

The full phytochemical profile of fig was revealed by UPLC-MS/MS. Prenylated flavonoids and prenylated coumarins were the characteristic phytochemicals. These data provided useful information for the extensive utilization of fig fruit in functional food. © 2023 Society of Chemical Industry.

Impact of germination pre-treatments on buckwheat and Quinoa: Mitigation of anti-nutrient content and enhancement of antioxidant properties

This study evaluated the effects of pre-germination treatments on the nutritional and anti-nutritional values of buckwheat and quinoa during germination. Pre-germination method was effective on the chemical composition and phenolic profile of buckwheat and quinoa samples (p < 0.05). During the germination, color changes were notable, particularly in the alkali-treated samples. The decrease in tannin content reached the highest rate in germinated buckwheat (83 %) and quinoa (20 %) by alkali treatment. The highest antioxidant and total phenolic content were measured in germinated pseudocereals treated by ultrasound. However, the lowest phytic acid content was determined after germination in the quinoa sample treated by ultrasound. Rutin was the major flavonoid in buckwheat while quercetin, galangin, ellagic, syringic, and p-coumaric acids were only synthesized after 72 h of germination. Catechin and epicatechin were decreased only in the alkali-treated buckwheat sample. Controlled germination processes can enhance the antioxidant activity and development of functional foods from whole grains.

Inactivation of Salmonella Typhimurium and Listeria monocytogenes on buckwheat seeds through combination treatment with plasma, vacuum packaging, and hot water

AIMS

The objectives of this study were to evaluate the effect of combination treatment with cold plasma (CP), vacuum packaging (VP), and hot water (HW) on the inactivation of foodborne pathogens on buckwheat seeds, and determined the germination rates of seeds and the quality of sprouts following combination treatment.

METHODS AND RESULTS

Buckwheat seeds inoculated with Salmonella Typhimurium and Listeria monocytogenes were treated with CP, HW, CP + HW, VP + HW, or CP + VP + HW. The germination rates of the HW-, CP + HW-, VP + HW-, and CP + VP + HW-treated seeds and the antioxidant activities and rutin contents of the CP + HW- and CP + VP + HW-treated sprouts were determined. HW, CP + HW, and CP + VP + HW were found to reduce the levels of the two pathogens to below the detection limit (1.0 log CFU g-1) at 70°C. However, HW and CP + HW significantly reduced the germination rate of buckwheat seeds. CP + VP + HW did not affect the germination rate of seeds nor the antioxidant activities and rutin content of buckwheat sprouts.

CONCLUSIONS

These results indicate that CP + VP + HW can be used as a novel control method to reduce foodborne pathogens in seeds without causing quality deterioration.

Optimization of ultrasound-assisted deep eutectic solvent extraction of bioactive compounds from pomegranate peel using response surface methodology

The efficient extraction of polyphenols from pomegranate peels using a deep eutectic solvent (DES) and ultrasound-assisted extraction (UAE) was investigated. A Box-Behnken design was used to investigate the effects of four independent variables (water content, liquid-to-solid ratio, ultrasonic power, and extraction time) on total polyphenol content (TPC), punicalagin content (PC), and ellagic acid content (EC). Optimized DES-based UAE conditions were as follows: TPC (water content, 29.30%; liquid-to-solid ratio, 53.50 mL/g; ultrasonic power, 238.20 W; extraction time, 29.50 min), PC (water content, 25.65%; liquid-to-solid ratio, 44.20 mL/g; ultrasonic power, 120 W; extraction time, 20 min), and EC (water content, 33.13%; liquid-to-solid ratio, 60 mL/g; ultrasonic power, 300 W; extraction time, 20 min). Under these optimal conditions, the experimental values for TPC, PC, and EC were 67.50 mg GAE/g, 130.65 mg/g, and 2.04 mg/g, respectively; these values were consistent with the predicted values.

Sustainable ultrasound-assisted extraction of Polygonatum sibiricum saponins using ionic strength-responsive natural deep eutectic solvents

The sustainable extraction of saponins was investigated using natural deep eutectic solvents (NADESs) combined with ultrasound-assisted extraction. A novel NADES (butyric acid-urea) that was responsive to ionic strength was designed and used as the extractant. Ultrasound treatment and a catalyst ferric chloride with plant cell wall breaking function were applied to improve the extraction efficiency.Since the solubility of the NADES varied significantly with ionic strength, 95% of NADES was readily separated from the water phase after the addition of sodium chloride, while saponins remained in the water phase for easy collection. The reuse capacity of NADES, the eco-friendliness of the extraction method, and the antioxidant activity of the extract were further evaluated.NADES was continuously recovered and used to extract Polygonatum sibiricum powder: the yield of saponins did not decrease after five cycles of recovery and re-extraction. The penalty point on the "Eco-scale" suggested that the extraction method was "green" (i.e. eco-friendly).Compared with ethanol extracts, the NADES extracts showed a higher saponin concentration and antioxidant activity.The study can contribute to the sustainable and green extraction of hydrophilic active substances in the food and pharmaceutical industries.

Factors Affecting the Extraction of (Poly)Phenols from Natural Resources Using Deep Eutectic Solvents Combined with Ultrasound-Assisted Extraction

Replacing conventional solvents with deep eutectic solvents (DES) has shown promising effects on the extraction yield of (poly)phenols. DES can be combined with ultrasound-assisted extraction (UAE) to further increase the extraction efficiency of (poly)phenols from natural resources compared to conventional methods. This review discusses the factors associated with DES (composition, solvent-to-sample ratio, extraction duration, and temperature) and UAE (ultrasound frequency, power, intensity, and duty cycle) methods that influence the extraction of (poly)phenols and informs future improvements required in the optimization of the extraction process. For the optimum (poly)phenol extraction from natural resources, the following parameters shall be considered: ultrasound frequency should be in the range of 20-50 kHz, ultrasound intensity in the range of 60-120 W/cm2, ultrasound duty cycle in the range of 40-80%, ultrasound duration for 10-30 minutes, and ultrasound temperature for 25-50 °C. Among the reported DES systems, choline chloride with glycerol or lactic acid, with a solvent-to-sample mass ratio of 10-30:1 shown to be effective. The solvent composition and solvent-to-sample mass ratio should be selected according to the target compound and the source material. However, the high viscosity of DES is among the major limitations. Optimizing these factors can help to increase the yield of extracted (poly)phenols and their applications.

Ultrasound-Assisted Deep Eutectic Solvent Extraction of Phenolic Compounds from Thinned Young Kiwifruits and Their Beneficial Effects

Fruit thinning is a common practice employed to enhance the quality and yield of kiwifruits during the growing period, and about 30-50% of unripe kiwifruits will be thinned and discarded. In fact, these unripe kiwifruits are rich in nutrients and bioactive compounds. Nevertheless, the applications of thinned young kiwifruits and related bioactive compounds in the food and functional food industry are still limited. Therefore, to promote the potential applications of thinned young kiwifruits as value-added health products, the extraction, characterization, and evaluation of beneficial effects of phenolic compounds from thinned young fruits of red-fleshed Actinidia chinensis cv 'HY' were examined in the present study. A green and efficient ultrasound-assisted deep eutectic solvent extraction (UADE) method for extracting phenolic compounds from thinned young kiwifruits was established. A maximum yield (105.37 ± 1.2 mg GAE/g DW) of total phenolics extracted from thinned young kiwifruits by UADE was obtained, which was significantly higher than those of conventional organic solvent extraction (CSE, about 14.51 ± 0.26 mg GAE/g DW) and ultrasound-assisted ethanol extraction (UAEE, about 43.85 ± 1.17 mg GAE/g DW). In addition, 29 compounds, e.g., gallic acid, chlorogenic acid, neochlorogenic acid, catechin, epicatechin, procyanidin B1, procyanidin B2, quercetin-3-rhamnoside, and quercetin-3-O-glucoside, were identified in the kiwifruit extract by UPLC-MS/MS. Furthermore, the contents of major phenolic compounds in different kiwifruit extracts prepared by conventional organic solvent extraction (EE), ultrasound-assisted ethanol extraction (UEE), and ultrasound-assisted deep eutectic solvent extraction (UDE) were compared by HPLC analysis. Results revealed that the content of major phenolics in UDE (about 15.067 mg/g DW) was significantly higher than that in EE (about 2.218 mg/g DW) and UEE (about 6.122 mg/g DW), suggesting that the UADE method was more efficient for extracting polyphenolics from thinned young kiwifruits. In addition, compared with EE and UEE, UDE exhibited much higher antioxidant and anti-inflammatory effects as well as inhibitory effects against α-glucosidase and pancreatic lipase, which were closely associated with its higher content of phenolic compounds. Collectively, the findings suggest that the UADE method can be applied as an efficient technique for the preparation of bioactive polyphenolics from thinned young kiwifruits, and the thinned young fruits of red-fleshed A. chinensis cv 'HY' have good potential to be developed and utilized as functional foods and nutraceuticals.

The Most Potent Natural Pharmaceuticals, Cosmetics, and Food Ingredients Isolated from Plants with Deep Eutectic Solvents

There is growing interest in reducing the number of synthetic products or additives and replacing them with natural ones. The pharmaceutical, cosmetic, and food industries are especially focused on natural and bioactive chemicals isolated from plants or microorganisms. The main challenge here is to develop efficient and ecological methods for their isolation. According to the strategies and rules of sustainable development and green chemistry, green solvents and environmentally friendly technologies must be used. The application of deep eutectic solvents as efficient and biodegradable solvents seems to be a promising alternative to traditional methods. They are classified as being green and ecological but, most importantly, very efficient extraction media compared to organic solvents. The aim of this review is to present the recent findings on green extraction, as well as the biological activities and the possible applications of natural plant ingredients, namely, phenolics, flavonoids, terpenes, saponins, and some others. This paper thoroughly reviews modern, ecological, and efficient extraction methods with the use of deep eutectic solvents (DESs). The newest findings, as well as the factors influencing the efficiency of extraction, such as water content, and hydrogen bond donor and acceptor types, as well as the extraction systems, are also discussed. New solutions to the major problem of separating DESs from the extract and for solvent recycling are also presented.

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.

Evaluating the status quo of deep eutectic solvent in food chemistry. Potentials and limitations

Conventional organic solvents (e.g., methanol, ethanol, ethyl acetate) are widely used for extraction, reaction, and separation of valuable compounds. Although these solvents are effective, they have disadvantages, including flammability, toxicity, and persistence in the environment. Deep eutectic solvents (DESs) are valued for their biodegradability/low impact on the environment, low cost, and ease of manufacture. The objective of this review was to provide an overview of applications of DES in food chemistry, specifically in regard of extraction of polyphenols (e.g., anthocyanin, rutin, kaempferol, quercetin, resveratrol), protein, carbohydrates (e.g., chitin, pectins), lipids and lipid-soluble compounds (e.g., free fatty acids, astaxanthin, β-carotene, terpenoids), biosensor development, and use in food safety (pyrethroids, Sudan I, bisphenol A, Pb²⁺, Cd²⁺, etc.) over the past five years. A comprehensive analysis and discussion of DES types, preparation, structures, and influencing factors is provided. Furthermore, the potential and disadvantages of using DESs to extract biomolecules were assessed. We concluded that DES is a viable alternative for extracting polyphenols, carbohydrates, and lipids as well as use in food safety monitoring and biosensor development. However, more work is needed to address shortcomings, and determine whether using compounds extracted with DES can be consumed safely.

Efficient extraction, excellent activity, and microencapsulation of flavonoids from Moringa oleifera leaves extracted by deep eutectic solvent

A deep eutectic solvent (choline chloride (ChCl)-urea) was chosen to extract flavonoids from Moringa oleifera leaves (FMOL), the condition of extraction was tailor-made, under the optimal extraction conditions (material-to-liquid ratio of 1:60 g/mL, extraction time of 80 min, extraction temperature of 80 °C), the highest extraction efficiency reached 63.2 ± 0.3 mg R/g DW, and nine flavonoids were identified. Then, the biological activities including antioxidant activities, antibacterial activities, and anti-tumor activities were systematically studied. FMOL was superior to positive drugs in terms of antioxidant activity. As to DPPH investigation, the IC50 of FMOL and Vc were 64.1 ± 0.7 and 176.1 ± 2.0 µg/mL; for the ABTS, the IC50 of FMOL and Vc were 9.5 ± 0.3 and 38.2 ± 1.2 µg/mL, the FRAP value of FMOL and Vc were 15.5 ± 0.6 and 10.2 ± 0.4 mg TE/g, and ORAC value of FMOL and Vc were 4687.2 ± 102.8 and 3881.6 ± 98.6 µmol TE/g. The bacteriostatic (MICs were ≤ 1.25 mg/mL) activities of FMOL were much better than propyl p-hydroxybenzoate. Meanwhile, FMOL had comparable inhibitory activity with genistein on tumor cells, IC50 was 307.8 µg/mL, and could effectively induce apoptosis in HCT116. Microcapsules were prepared with xylose-modified soybean protein isolate and gelatin as wall materials; after that, the intestinal release of modified FMOL microcapsules was 86 times of free FMOL. Therefore, this study confirmed that FMOL extracted with ChCl/urea has rich bioactive components, and microencapsulated FMOL has potential application in food industry.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13399-023-03877-8.

Extraction, separation and kinetics of phenylethanosides from Plantago asiatica L. by an innovative extraction technology-deep eutectic solvent-based ultrasound-assisted extraction

In this paper, the total phenylethanosides (TPS) were extracted efficiently by an innovative extraction technology--deep eutectic solvent-based ultrasound-assisted extraction (DES-UAE) from Plantago asiatica L. Ten diverse types of DESs were synthesized as alternative extraction solutions. The extraction efficiency of DES-3 (constituted by choline chloride and lactic acid) was much higher than those of other DESs. On the basis of single factor tests and Box-Behnken design (BBD), the optimum processing parameters of DES-UAE as follow: DES-3 with molar ratio of 1:3, extraction temperature 51 °C, solid/liquid 22.5 mg/ml, water content 30%, ultrasonic power 65 W, extraction time 23 min. The extraction efficiency of TPS from Plantago asiatica L. was 8.395 mg/ml, which was more superior than those of organic solvents (water, methanol, 50% methanol, ethanol, 50% ethanol). The extraction kinetics experiment results showed that water content had a significant influence upon the extraction efficiency of TPS. At the same time, AB-8 macroporous resin column was used to efficiently isolate TPS from DES extraction with a recovery rate of 88.5%.

Meireles M, Ibáñez E. Synergic effect of natural deep eutectic solvent and high-intensity ultrasound on obtaining a ready-to-use genipin extract: Crosslinking and anti-neurodegenerative properties

In this paper, genipin, an important natural crosslinker and anti-neurodegenerative compound, was extracted from unripe Genipa americana L., combining high-intensity ultrasound (HIUS) and natural deep eutectic solvents (NADESs). The extraction process conditions were evaluated step-by-step to reach the best genipin recovery. The obtained ready-to-use genipin-NADES extract was examined regarding its crosslinking properties and anti-neurodegenerative capacity. For the condictions tested, the highest genipin recovery was obtained using 40 % water and 60 % betaine:lactic acid NADES in molar ratio 1:3 (n/n) as the solvent, a solvent:feed ratio of 19 (w/w), and HIUS acoustic power of 14 ± 1 W. The HIUS-assisted extraction using NADES as solvent showed to be a promising and efficient green extraction technique to obtain genipin. The ready-to-use genipin-NADES extract presented crosslinking capacity and anticholinergic activity. These results indicate that genipin-NADES extract can be directly applied in hydrogels for drug delivery, films, tissue engineering, and others. Moreover, it can be used in food, supplements, and medicine to enhance their neuroprotective effect.

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.

Deep Eutectic Liquids as Tailorable Extraction Solvents: A Review of Opportunities and Challenges

Deep Eutectic Liquids (DELs) fall among the rapidly evolving discoveries of the 21st century, and these liquids are considered as alternative solvents to toxic and volatile organic liquids. Nevertheless, the emerging trend regarding the use of DELs in every field of physical and biological sciences, a lot of ambiguities and misconceptions exist about their formation, mechanism, and efficiencies observed or projected. A review of available technical data makes it obvious that these liquids have the potential to revolutionize the underdeveloped areas of analytical chemistry particularly the extraction/enrichment of analytes. To ensure the green and sustainable use of DELs, the researchers need to have a thorough understanding of DELs, their classification, chemistry, the nature and strength of molecular entanglements, and their tailorable features. Many researchers have declared these liquids recyclable but more attentive trials are needed to develop an authentic and straightforward DELs recycling methodology. The present review covers sound background knowledge and expert opinions about the technical definition of DELs, their classification, formation, recyclability, and tailorable features for their application as extraction solvent/sorbent in analytical chemistry.

High-voltage pulse-assisted extraction of flavonoids from kapok using deep eutectic solvent aqueous solutions

In this study, deep eutectic solvents coupled with a pulsed electric field (PEF-DES) were first applied to the extraction of traditional Chinese medicine plants. This study uses the PEF-DES extraction technique to extract TG-KF (Kapok flavonoid solution extracted with DES-TG). PEF-DES is a simple, effective and environmentally-friendly technology and can be used in industrial-scale production. For the optimal extraction conditions of TG-KF, DES-TG was used as a solvent, the DES-TG concentration was 50%, the solid-liquid ratio was 1 : 30, the electric field intensity was 0.55 kV cm-1, the number of pulses was 100, and the yield of flavonoids was 14.36 ± 0.35%. TG-KF has very good stability and there is no precipitation or discoloration within 6 months. The results of chicken embryo experiments and human patch tests show that 10% TG-KF aqueous solution has no irritation. DPPH experiments show that TG-KF has excellent efficacy as an antioxidant. Overall, TG-KF is expected to become a potential antioxidant raw material.

Phenolic compounds in common buckwheat sprouts: composition, isolation, analysis and bioactivities

Phenolic compounds in common buckwheat sprouts (CBSs) have gained research interest because of their multiple health benefits. Phenolic acids, flavanones, flavonols, flavan-3-ols, and anthocyanins are important bioactive components of CBS that exhibit biological activities, including anti-inflammatory, antioxidant, anti-proliferative, and immunomodulatory effects. The isolation and quantitative and qualitative analyses of these phenolic compounds require effective and appropriate extraction and analytical methods. The most recent analytical method developed for determining the phenolic profile is HPLC coupled with a UV-visible detector and/or MS. This review highlights the extraction, purification, analysis, and bioactive properties of phenolic compounds from CBS described in the literature.

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 Compounds From Cannabis sativa L. Flowers and/or Leaves Using Deep Eutectic Solvents

The increasing demand for medical cannabis urges the development of new and effective methods for the extraction of phytocannabinoids. Deep eutectic solvents (DESs) are an alternative to the use of hazardous organic solvents typically used in the industry. In this study, hydrophilic and hydrophobic DESs were developed based on terpenes, sugars, and natural organic acids as green extraction media for the extraction of cannabis bioactive compounds. The factors influencing the extraction of bioactive components, such as the type of DESs and extraction time, were investigated. Initial screening in hemp showed that the DES composed of Men: Lau (a 2:1-M ratio) had a greater extraction efficiency of cannabidiol (CBD) and cannabidiolic acid (CBDA) (11.07 ± 0.37 mg/g) of all the tested DESs and higher than ethanol. Besides having a higher or equivalent extraction yield as the organic solvents tested, DESs showed to be more selective, extracting fewer impurities, such as chlorophyll and waxes. These results, coupled with the non-toxic, biodegradable, low-cost, and environmentally friendly characteristics of DESs, provide strong evidence that DESs represent a better alternative to organic solvents.

Impact of low-frequency ultrasound technology on physical, chemical and technological properties of cereals and pseudocereals

Cereals (CE) and pseudocereals (PSCE) play a pivotal role in nourishing the human population. Low-frequency ultrasound (LFUS) modifies the structure of CE and PSCE macromolecules such as starch and proteins, often improving their technological, functional and bioactive properties. Hence, it is employed for enhancing the traditional processes utilized for the preparation of CE- and PSCE-based foods as well as for the upcycling of their by-products. We report recent advances in LFUS treatments for hydration, germination, extraction of bioactive compounds from by-products, and fortification of CEs and PSCE, including kinetic modelling and underlying action mechanisms. Meta-analyses of LFUS influence on compounds extraction and starch gelatinization are also presented. LFUS enhances hydration rate and time lag phase of CE and PSCE, essential for germination, extraction, fermentation and cooking. The germination is improved by increasing hydration, releasing promoters and eliminating inhibitors. Furthermore, LFUS boosts the extraction of phenolic compounds, polysaccharides and other food components; modifies starch structure, affecting pasting properties; causes partial denaturation of proteins, improving their interfacial properties and their peptides availability. Overall, LFUS has an outstanding potential to improve transformation processes and functionalities of CE and PSCE.

Iridoid Glycosides from Phlomis Medicinalis Diels: Optimized Extraction and Hemostasis Evaluation

Phlomis medicinalis Diels, an important perennial herbal plant unique to the Qinghai-Tibet Plateau, is often used as Tibetan Materia Medicine Radix Phlomii for the treatment of cold, cough, and convergence trauma. In order to efficiently extract the iridoid glycosides from P. medicinalis, an ultrasound-assisted deep eutectic solvent extraction technique was employed. The main parameters influencing the extraction process were studied through single-factor tests and the extraction was optimized by using response surface methodology. The hemostasis activity of total iridoid glycosides (TIG) from P. medicinalis was evaluated in vitro and in mice. The optimization results revealed that the optimal process parameters were liquid-solid ratio 20 : 1, choline chloride-lactic acid concentration 79 %, and sonication time 34 min, under which a TIG extraction yield of 20.73 % was obtained. Meanwhile, high-performance liquid chromatography-photodiode array/mass spectrometry (HPLC-PDA/MS) was employed to characterize the optimized extract and indicated that TIG from P. medicinalis mainly consisted of sixteen reported iridoid glycosides with a total content of 91.22 %. The experimental results in vivo and in vitro indicated that TIG from P. medicinalis had strong hemostasis activities, which may be achieved by increasing the fibrinogen levels. Therefore, the ultrasound-assisted deep eutectic solvent extraction is an effective method to extract iridoid glycosides from P. medicinalis and they will be promising candidates to be developed for medical hemostasis agents.

The ability of deep eutectic solvent systems to extract bioactive compounds from apple pomace

The objective of this study was to examine the bioactivity of extracts from apple pomace obtained by non-conventional green extraction methods (DES systems). Bioactivity was antioxidant capacity and ability to stimulate insulin secretion from pancreatic beta-cells. The antioxidant capacity of extracts was examined using the DPPH and the FRAP assay. Impact of the extracts on cell viability and insulin secretion were examined using the BRIN-BD11 cell line. ChCl:EG(1:4) extracts resulted in high antioxidant capacity in the DPPH assay (80.1% inhibition versus 11.3%). Extracts obtained from the classical systems demonstrated an ability to promote insulin secretion significantly higher than the positive control, p < 0.05. ChCl:EG(1:4) extracts stimulated insulin secretion to a lesser extent. Overall, the data provides evidence for the potential of DES systems to extract bioactive compounds from apple pomace that have relevance for metabolic health. Further optimisation of the extraction procedures should be tailored to the desired bioactive properties.

Deep Eutectic Solvent as Green Solvent in Extraction of Biological Macromolecules: A Review

Greater awareness of environmental sustainability has driven many industries to transition from using synthetic organic solvents to greener solvents in their manufacturing. Deep eutectic solvents (DESs) have emerged as a highly promising category of green solvents with well-demonstrated and wide-ranging applications, including their use as a solvent in extraction of small-molecule bioactive compounds for food and pharmaceutical applications. The use of DES as an extraction solvent of biological macromolecules, on the other hand, has not been as extensively studied. Thereby, the feasibility of employing DES for biomacromolecule extraction has not been well elucidated. To bridge this gap, this review provides an overview of DES with an emphasis on its unique physicochemical properties that make it an attractive green solvent (e.g., non-toxicity, biodegradability, ease of preparation, renewable, tailorable properties). Recent advances in DES extraction of three classes of biomacromolecules-i.e., proteins, carbohydrates, and lipids-were discussed and future research needs were identified. The importance of DES's properties-particularly its viscosity, polarity, molar ratio of DES components, and water addition-on the DES extraction's performance were discussed. Not unlike the findings from DES extraction of bioactive small molecules, DES extraction of biomacromolecules was concluded to be generally superior to extraction using synthetic organic solvents.

Ultrasound-Assisted Natural Deep Eutectic Solvent Extraction and Bioactivities of Flavonoids in Ampelopsis grossedentata Leaves

We performed ultrasound-assisted extraction coupled with natural deep eutectic solvents (NADES) to achieve the green and efficient preparation of flavonoid extract from Ampelopsis grossedentata leaves. We then evaluated its antioxidant and antiproliferative activities. A NADES consisting of choline chloride and glucose at a molar ratio of 4:1 with 20% water was determined to be the most suitable solvent. The optimal extraction conditions were: a liquid-to-solid ratio of 30 mL/g, an ultrasonication power of 490 W, and an ultrasonication time of 6.5 min. The actual flavonoid yield was 83.93%, which was close to the predicted yield. Further, 86.75% of the flavonoids were recovered by adding the same volume of phosphate buffer saline (100 mM, pH of 7.0) to the extract solution. Although the chemical antioxidant activities of the flavonoid extract were slightly inferior to those of dihydromyricetin, the flavonoid extract could still effectively inhibit the proliferation of human breast MDA-MB-231 cells by inducing cell apoptosis, retarding the cell cycle, changing the mitochondrial membrane potential and scavenging intracellular reactive oxygen species (ROS). The obtained results can provide a reference in the development of plant-derived functional foods.

A Green Method of Extracting and Recovering Flavonoids from Acanthopanax senticosus Using Deep Eutectic Solvents

In recent years, green extraction of bioactive compounds from herbal medicines has generated widespread interest. Deep eutectic solvents (DES) have widely replaced traditional organic solvents in the extraction process. In this study, the efficiencies of eight DESs in extracting flavonoids from Acanthopanax senticosus (AS) were compared. Response surface methodology (RSM) was employed to optimize the independent variable including ultrasonic power, water content, solid-liquid ratio, extraction temperature, and extraction time. DES composed of glycerol and levulinic acid (1:1) was chosen as the most suitable extraction medium. Optimal conditions were ultrasonic power of 500 W, water content of 28%, solid-liquid ratio of 1:18 g·mL⁻¹, extraction temperature of 55 °C, and extraction time of 73 min. The extraction yield of total flavonoids reached 23.928 ± 0.071 mg·g⁻¹, which was 40.7% higher compared with ultrasonic-assisted ethanol extraction. Macroporous resin (D-101, HPD-600, S-8 and AB-8) was used to recover flavonoids from extracts. The AB-8 resin showed higher adsorption/desorption performance, with a recovery rate of total flavonoids of up to 71.56 ± 0.256%. In addition, DES solvent could efficiently be reused twice. In summary, ultrasonic-assisted DES combined with the macroporous resin enrichment method is exceptionally effective in recovering flavonoids from AS, and provides a promising environmentally friendly and recyclable strategy for flavonoid extraction from natural plant sources.

Exploration of a ternary deep eutectic solvent for the efficient extraction of plantamajoside, acteoside, quercetin and kaempferol from Plantago asiatica L

INTRODUCTION

In the present study, ternary deep eutectic solvent-based ultrasound-assisted extraction was developed for the efficient extraction of plantamajoside, acteoside, quercetin and kaempferol from Plantago asiatica L.

METHODOLOGY

Six kinds of choline chloride-based ternary deep eutectic solvents (TDESs) were prepared as potential extraction solutions. In order to obtain optimal extraction efficiency, a series of extraction conditions were investigated by single-factor test and orthogonal test.

RESULTS

The extraction efficiency of choline chloride/lactic acid/ethylene glycol (ChCl-LA-EG) was much higher than that of other TDESs. ChCl-LA-EG-11 synthesised with choline chloride, lactic acid and ethylene glycol (1:4:2) was considered to have a higher extraction efficiency. The optimal ultrasound-assisted extraction conditions were as follows: water content in ChCl-LA-EG-11, 50%; extraction temperature, 70°C; ratio of solid/liquid, 20 mg/mL; ultrasonic power, 60 W; extraction time, 35 min; pH of the solution, 8. Under the optimal extraction conditions, the extraction efficiencies of plantamajoside, acteoside, quercetin and kaempferol were 3.83 ± 0.41, 4.23 ± 0.45, 0.56 ± 0.15 and 0.19 ± 0.08 mg/g, respectively. The extraction efficiency of the total target components was 9.21 ± 0.63 mg/g, which was much higher than that of conventional solvents (water, methanol, ethanol, 50% methanol, 50% ethanol). The target components were isolated efficiently from the TDES solution by an AB-8 macroporous resin column with a recovery rate of 95.6%.

CONCLUSION

This study demonstrated that TDESs possessed excellent physical and chemical properties and had enormous potential for active component extraction of traditional Chinese medicinal materials.