Extraction of caffeine and polyphenols from kola nuts by ultrasound-assisted extraction and natural deep eutectic solvent

Mangosteen (Garcinia mangostana L.) peel is a potential source of phenolic compounds with beneficial properties. Natural deep eutectic solvents (NaDES) have been considered an environmentally friendly and cheap alternative to conventional organic solvents. In this work, a green extraction methodology was developed using ultrasound-assisted extraction (UAE) and NaDES for the extraction of antioxidant non-extractable polyphenols (NEPs) from mangosteen peel. To select the best NaDES to extract NEPs from mangosteen peel, seven NaDES were studied. Antioxidant capacity and total phenolic and proanthocyanidin contents were determined for the extracts. The molecular weights for the NEPs present in those extracts were evaluated by size exclusion chromatography. Experimental results showed that choline chloride–lactic acid (1:2) was the NaDES allowing the highest antioxidant proanthocyanidin content in the extracts. A Box–Behnken experimental design was employed to optimize the main parameters in UAE with NaDES: water percentage, ultrasound amplitude, and extraction time. The optimal extraction conditions were 18.8% (v/v) water, 60% ultrasound amplitude, and 15 min as the extraction time. In addition, the cytotoxicity of the NEP extracts obtained under optimal extraction conditions was evaluated. Results indicated for the first time that the use of NaDES in combination with UAE could be a sustainable alternative for the extraction of antioxidant NEPs from mangosteen peel for important applications in the food, pharmaceutical, agrochemical, and cosmetic fields, as the extracts presented low cytotoxicity.

In this study, an environmentally friendly and efficient method based on natural deep eutectic solvent (NADES) in combination with ultrasound-assisted extraction was used for the recovery of phenolic compounds from apple pomace. Acidic, alkaline, sugar-based and polyol-based NADESs were examined for extraction of total phenolic content from apple pomace under different conditions.NADES type, biomass percentage, extraction temperature, extraction time and water content were the testing parameters. NADES type and water content of the solvent were the most important parameters that affected the extraction yield. The most effective NADESs were sugar-based NADESs, which were followed by acidic NADESs. Up to 9.47 mgGAE/gapple pomacewas recovered from apple pomace with glucose:sucrose:water. The highest total flavonoid content was obtained with choline chloride:urea as 17.30 mgEPE/gapple pomace. On the other hand, NADES composed of choline chloride – lactic acid was found to exhibit a significant antioxidant activity. The novelty of this article is the investigation of acidic, alkaline, sugar-based and polyol-based NADESs in the recovery of phenolic compounds from apple pomace using ultrasound-assisted extraction, for the first time in the literature. The antioxidant activity of extracts were also explained in combination with that of NADESs.

Conventional extraction techniques are usually based on highly pollutant and/or flammable organic solvents. Therefore, alternative environmentally friendly extraction methods are of particular interest for the recovery of bioactive compounds for their application as food ingredients and/or nutraceuticals. Natural deep eutectic solvents (NADES) are a green and nontoxic attractive alternative to hydroalcoholic extraction. NADES media primarily depends on the intermolecular interactions (hydrogen bonding) among their components to form a eutectic mixture with a much lower final melting point than its individual components. Examples of natural deep eutectic NADES solvents include aqueous solutions (25%–50% water) of choline chloride, sugars, and polyols. This study aimed to investigate the application of two NADES, namely, betaine:triethylene glycol (Bet : TEG) and choline chloride:1,2-propanediol (Chol : Prop), as sustainable green solvents for the extraction of polyphenols from spent coffee ground (SCG), a by-product of coffee processing. In particular, the extraction yield and selectivity were evaluated and compared with conventional green extractions (hot water and a hydroalcoholic solution). In addition, the effect of NADES on the antioxidant and antimicrobial activity of the extracts was investigated. The main outcomes were as follows: (i) NADES were as effective as other conventional green solvents in the extraction of polyphenols with the added advantage of operating at milder temperature conditions, without flammable solvents and with sustainable and natural compounds; (ii) the antimicrobial activity of the NADES extracts was 10 times higher than that of the ethanolic and aqueous extracts. Given the low toxicity of NADES, they could be used as formulation aid for food ingredients.

Green extraction of bioactive compounds from apple pomace by ultrasound assisted natural deep eutectic solvent extraction: Optimisation, comparison and bioactivity

The Lempuyang plant is one of the medicinal plants in Indonesia. One of the plants of the Lempuyang family that has not been widely researched is Lempuyang Gajah Zingiber zerumbet (L.). The commonly used method of extraction of phenolic compounds is maceration with organic solvents. The disadvantages are the amount of organic solvents that must be used and the long extraction time (days). An environmentally friendly solvent that has been successfully developed in the 21st century is eutectic or known as Natural deep eutectic solvent (NADES). In addition, NADES can also be used in conjunction with other extraction methods such as (UAE), and microwave aid (MAE). The results obtained were the synthesis of NADES with HBA (Choline Chloride) and HBD variations (Glucose, Lactic Acid, and Ethylene Glycol) with ratios of 1:1 and 1:2. In the maceration process, variations in time (2, 4, 6 hours) and variations in extraction methods (maceration, UAE and UAE-MAE) are carried out. The best TFC (Total Flavonoid Content) value data was obtained by NADES D (choline chloride: glycerol 1:2) of 697.24 mg QE/g extract through a combined ultrasonic and microwave method (UAE-MAE) while the best TPC (Total Phenolic Content) was NADES C (choline chloride: glycerol 1:1) of 2491.88 mg GA/g extract through a combined ultrasonic and microwave method (UAE-MAE). Meanwhile, the characterization of NADES synthesis to see the interaction of hydrogen bonds through FTIR analysis, and the content of phenolic compounds and flavonoids was carried out through HPLC-DAD.

Ultrasound-assisted extraction using natural deep eutectic solvent of secondary metabolites from Tagetes erecta flowers irradiated with UVC light

Kinkeliba (C. micranthum) is a tropical plant widely used for its tremendous phytochemicals and biological activities. In the present study, three green carboxylic acid-based natural deep eutectic solvents (NADESs) were used to assess the extraction of phenolic compounds in terms of total phenolic content (TPC), total flavonoid content (TFC), individual phenolic compounds and antioxidant capacity (DPPH and FRAP assays) from dried C. micranthum leaves. For the synthesis of NADESs choline chloride was used as hydrogen bond acceptors (HBA) in combination with lactic acid (ChLa), acetic acid (ChAa) and tartaric acid (ChTa) as hydrogen bond donors (HBDs). The conventional solvents including distilled water, pure methanol and pure ethanol were used for comparison. Three extraction methods including maceration extraction (ME), homogenate-assisted extraction (HAE) and ultrasound-assisted extraction (UAE) were tested to determine the best extraction conditions. The solvents combined with the extraction methods were successfully applied for the recovery of phenolic compounds from C. micranthum leaves. ChLa exhibited the highest performance giving the TPC (21.12 ± 0.13–23.62 ± 0.58 mg GAE/g, followed by ChAc (15.49 ± 0.13–18.85 ± 0.39 mg GAE/g), water (17.08 ± 0.32–18.13 ± 0.13 mg GAE/g), ChTa (14.49 ± 0.26–17.44 ± 0.19 mg GAE/g), methanol (7.46 ± 0.45–11.64 ± 0.32 mg GAE/g) and ethanol (2.88 ± 0.39–4.60 ± 0.39 mg GAE/g), respectively. For TFC, ChLa (4.38 ± 0.09–5.01 ± 0.09 mg ECE/g) was the most prominent solvent, followed by ChAc (2.84 ± 0.04–5.01 ± 0.36 mg ECE/g), methanol (1.93 ± 053–4.85 ± 0.04 mg ECE/g), ethanol (1.49 ± 0.36–4.16 ± 0.04 mg ECE/g), ChTa (1.09 ± 0.04–3.22 ± 0.13 mg ECE/g) and water (1.15 ± 0.04–1.37 ± 0.44 mg ECE/g), respectively. The acidic NADESs especially ChLa and ChAa exhibited the best efficiencies compared to the conventional solvents. Furthermore, UAE and HAE provided good extraction efficiency in a short extraction time (30 min) in terms of the TPC, TFC, individual phenolic compounds and the antioxidant capacity compared to ME which gave a similar yield with 12 h of extraction time. Principal component analysis (PCA) showed that C. micranthum extracts could clearly be discriminated in terms of phytochemical compounds and antioxidant capacity and UAE, HAE or ME combined with ChLa ChAc or ChTa were the best choices to higher extraction efficiency.

In the present study, natural deep eutectic solvents (NADES) as a novel green tool were used for the recovery of bioactive compounds with respect to the valorization of artichoke outer petals. NADES coupled with ultrasound-assisted extraction was applied by varying the type of hydrogen bond acceptors (choline chloride or betain) and hydrogen bond donors (sucrose, lactic acid, citric acid, oxalic acid and glycerol) in the NADES mixtures. Thereafter, extraction efficacy was assessed in terms of total phenolic content, antioxidant capacity and individual phenolic composition and their levels by comparing the results obtained by NADES with those for a reference methanolic extract. Based on the results of the present study, the use of choline chloride and lactic acid mixtures was superior for obtaining extracts with high levels of phenolic compounds (12.96 g GAE kg-1 DW) and high antioxidant potential (60.68 g TE kg-1 DW). In addition, gallic acid, syringic acid, chlorogenic acid, ferulic acid, sinapic acid, luteolin, apigenin, rutin and quercetin were detected in all extracts by chromatographic evaluation. As major phenolic compounds, chlorogenic acid and ferulic acid were found to be maximum in lactic acid-based NADES mixtures. The present study reveals the potential treatment of various plants, wastes or by-products with NADES combined with an ultrasonication method for the extraction of bioactive compounds with enhanced recovery and selectivity, with the aim of incorporating them into various food and pharmaceutical formulations. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

This investigation focused on assessing and enhancing ultrasound‐assisted extraction (UAE) using natural deep eutectic solvents (NADES) to extract phenolics and terpenoids from sweet basil leaves. The initial stage involved evaluating the extraction performance of twelve NADES and ethanol. A NADES comprising lactic acid and glucose with a 2 : 1 molar ratio and 20% water content (WC) obtained the highest total phenolic content (TPC) and total terpenoid content (TTC). Single‐factor experiments systematically examined the impact of liquid‐to‐solid ratio (LSR), water content in NADES (WC), ultrasound power, temperature, and exposure time on the extraction yield. Optimization using Box–Behnken Design (BBD) models for the lactic acid and glucose‐based UAE revealed the optimal conditions to be 80 ml/g LSR, 30% water, 300 W, 50°C temperature, and a 15‐minute exposure time. Under these optimized parameters, the extraction achieved the highest TPC and TTC at 69.88 mg GAE/g and 110.71 mg UA/g, respectively. This study presents an environmentally friendly and sustainable extraction protocol for the extraction of phenolic compounds and terpenoids from sweet basil leaves.

Eco-friendly extraction of six different rosemary (Rosmarinus officinalis L.) genotypes-using natural deep eutectic solvents: Optimization and modeling via response surface methodology (RSM)

Bilberry fruits (Vaccinium myrtillus L.) are one of the richest natural sources of anthocyanins and are widely used due to their pharmacological and nutritional properties. To ensure their maximum application potential, it is necessary to overcome the limitations of conventional extraction solvents and techniques. This study aimed to develop a green method for bilberry anthocyanin extraction using natural deep eutectic solvents (NaDES) integrated with ultrasound-assisted extraction (UAE) in order to define extraction conditions that will prevent decomposition of the anthocyanins or the loss of bioactivity. After a screening of ten different NaDES, choline chloride:sorbitol (1:1) was selected as the most effective. Furthermore, the influence analysis and optimization of the NaDES–UAE extraction conditions were carried out employing response surface methodology. The optimal conditions were found to be an extraction time of 37.63 min, a temperature of 48.38 °C, and 34.79% (w/w) water in NaDES. The extraction yields of target compounds under optimized extraction conditions were 0.27 mg/g DW of cyanidin-3-O-glucoside and 2.12 mg CGE/g DW of TAC. The obtained optimized extract showed promising radical scavenging and antimicrobial activity. A stability study with the optimized extract revealed that refrigerated storage at 4 °C in the dark provided the best anthocyanins preservation. Overall, the developed NaDES-UAE method showed promising application potential and can be considered as a high-efficiency green alternative to conventional anthocyanins extraction methods, enabling the preservation of active ingredients and the bioactivity of extracts.

“Novel chitosan/alginate hydrogels as carriers of phenolic-enriched extracts from saffron floral by-products using natural deep eutectic solvents as green extraction media”

Development and optimization of green extraction process of spent coffee grounds using natural deep eutectic solvents

Optimization of betaine-sorbitol natural deep eutectic solvent-based ultrasound-assisted extraction and pancreatic lipase inhibitory activity of chlorogenic acid and caffeine content from robusta green coffee beans

Due to increasing consumer awareness, there is a growing demand for healthy foods by replacing synthetic colorants with natural alternatives. Amaranthus is a sustainable rich source of one such natural colorant, namely, betalains. Conventional extraction methods have various challenges, such as high solvent requirements and low extraction yield. To overcome these problems, the present study aims at developing a green extraction method for betalains from Amaranth by ultrasound-assisted extraction (UAE) employing natural deep eutectic solvents (NADES). Of the three Amaranth species screened, the leafy Amaranth is found to have the highest betalains content (24.79 ± 2.88mg/100g FW). Among the five NADES screened, lactic acid: fructose was identified as the most efficient solvent with a betalains yield of 79.68 ± 4.81mg/100g FW. The Box-Behnken Design (BBD) was employed to identify the best combinations of extraction process parameters. This approach enabled optimization through a reduced number of experiments. Subsequently, a machine learning model was employed to predict yield for all possible process parameter combinations. On identifying the most effective combination process parameters that resulted in the highest possible yield (306.72mg/100g FW), the same is experimentally validated (297.28 ± 10.76mg/100g FW). UAE employing NADES has resulted in a 3.7-fold increase in the yield of betalains over extraction with NADES alone and a 12-fold increase over conventional extraction. HPLC analysis confirmed that the structure remained intact even after processing. Based on the results, UAE employing NADES was demonstrated to be an attractive extraction methodology for downstream processing of betalains in particular and biomolecules, in general.