The Effect of Ultrasonication Pretreatment on the Production of Polyphenol-Enriched Extracts from Moringa oleifera L. (Drumstick Tree) Using a Novel Bio-Based Deep Eutectic Solvent

Extraction of Protein and Bioactive Compounds from Mediterranean Red Algae (Sphaerococcus coronopifolius and Gelidium spinosum) Using Various Innovative Pretreatment Strategies

In this study, the release of proteins and other biomolecules into an aqueous media from two red macroalgae (Sphaerococcus coronopifolius and Gelidium spinosum) was studied using eight different cell disruption techniques. The contents of carbohydrates, pigments, and phenolic compounds coextracted with proteins were quantified. In addition, morphological changes at the cellular level in response to the different pretreatment methods were observed by an optical microscope. Finally, the antioxidant capacity of obtained protein extracts was evaluated using three in vitro tests. For both S. coronopifolius and G. spinosum, ultrasonication for 60 min proved to be the most effective technique for protein extraction, yielding values of 3.46 ± 0.06 mg/g DW and 9.73 ± 0.41 mg/g DW, respectively. Furthermore, the highest total contents of phenolic compounds, flavonoids, and carbohydrates were also recorded with the same method. However, the highest pigment contents were found with ultrasonication for 15 min. Interestingly, relatively high antioxidant activities like radical scavenging activity (31.57-65.16%), reducing power (0.51-1.70, OD at 700 nm), and ferrous iron-chelating activity (28.76-61.37%) were exerted by the different protein extracts whatever the pretreatment method applied. This antioxidant potency could be attributed to the presence of polyphenolic compounds, pigments, and/or other bioactive substances in these extracts. Among all the used techniques, ultrasonication pretreatment for 60 min appears to be the most efficient method in terms of destroying the macroalgae cell wall and extracting the molecules of interest, especially proteins. The protein fractions derived from the two red macroalgae under these conditions were precipitated with ammonium sulfate, lyophilized, and their molecular weight distribution was determined using SDS-PAGE. Our results showed that the major protein bands were observed between 25 kDa and 60 kDa for S. coronopifolius and ranged from 20 kDa to 150 kDa for G. spinosum. These findings indicated that ultrasonication for 60 min could be sufficient to disrupt the algae cells for obtaining protein-rich extracts with promising biological properties, especially antioxidant activity.

Response Surface Optimization for the Enhancement of the Extraction of Bioactive Compounds from Citrus limon Peel

Citrus limon is among the species of the genus Citrus that dominates the world market. It is highly nutritious for humans as it contains twice the amount of the suggested daily intake of ascorbic acid and is also a good source of phenolic compounds, carotenoids, and other bioactive compounds. This study aimed to identify the optimal extraction procedures and parameters to obtain the maximum quantity of bioactive components from lemon peel by-products. Various extraction techniques, including stirring, ultrasound, and pulsed electric field, were evaluated, along with factors such as extraction time, temperature, and solvent composition. The results revealed that simple stirring for 150 min at 20 °C proved to be the most effective and practical method. The ideal solvent mixture consisted of 75% ethanol and 25% water, highlighting the crucial role of solvent composition in maximizing extraction efficiency. Among the extracted compounds were phenolics, ascorbic acid, and carotenoids. Under optimum extraction conditions, the extract was found to contain high total phenolic content (TPC) (51.2 mg of gallic acid equivalents, GAE/g dry weight), total flavonoid content (TFC) (7.1 mg of rutin equivalents, RtE/g dry weight), amounts of ascorbic acid (3.7 mg/g dry weight), and total carotenoids content (TCC) (64.9 μg of β-carotene equivalents, CtE/g). Notably, the extracts demonstrated potent antioxidant properties (128.9 μmol of ascorbic acid equivalents, AAE/g; and 30.3 μmol of AAE/g as evidenced by FRAP and DPPH assays, respectively), making it a promising ingredient for functional foods and cosmetics. The study's implications lie in promoting sustainable practices by converting lemon peel into valuable resources and supporting human health and wellness through the consumption of natural antioxidants.

Optimization of Extraction Parameters for Enhanced Recovery of Bioactive Compounds from Quince Peels Using Response Surface Methodology

Quinces are well known for their multiple health benefits, including antioxidant, hypoglycemic, antimicrobial, anti-inflammatory, anticarcinogenic, etc., properties. Despite the widespread utilization of various plant parts, the peel has been largely ignored in the industry. In this study, we explored the effects of different extraction parameters, such as temperature, time, and composition of the extraction solvent, and techniques such as ultrasound (US) and a pulsed electric field (PEF), either alone or in combination, and optimized these parameters using a response surface methodology (RSM) to enhance the extraction of bioactive compounds such as chlorogenic acid, total polyphenols, flavonoids, and ascorbic acid from waste quince peels. From our results, it was apparent that quince peels are a great source of many bioactive compounds with high antioxidant activity. More specifically, after principal component analysis (PCA) and partial least squares (PLS) analysis, quince peels contain high levels of total polyphenols (43.99 mg gallic acid equivalents/g dw), total flavonoids (3.86 mg rutin equivalents/g dw), chlorogenic acid (2.12 mg/g dw), and ascorbic acid (543.93 mg/100 g dw), as well as antioxidant activity of 627.73 μmol AAE/g and 699.61 μmol DPPH/g as evidenced by FRAP and DPPH assays, respectively. These results emphasize the potential of utilizing quince peels as an eco-friendly and cost-effective source of bioactive compounds with various applications in the food and pharmaceutical industries for the prepared extracts.

Encapsulation of Moringa oleifera Extract in Ca-Alginate Chocolate Beads: Physical and Antioxidant Properties

The aim of the present study was to evaluate the physical and antioxidant properties of chocolate alginate beads containing Moringa oleifera leaf extract (MLE) produced with ecofriendly solvent extraction technology (Deep Eutectic Solvents). The concentration of MLE incorporated was 0, 2, 4, and 6% $\text{w}/\text{w}$ , and hardening time for ionotropic gelation with CaCl2 solution was 2, 8, or 20 min. Freshly prepared beads were evaluated for their geometric (area, perimeter, ferret diameter, circularity, roundness), color (CIE L ${}^{\ast }$ , a ${}^{\ast }$ , and b ${}^{\ast }$ and chroma), and antioxidant properties (total phenolic content and percentage inhibition of DPPH• radical). Increasing the MLE concentration resulted in beads smaller in size and more spherical, whereas hardening time only affected their circularity. MLE concentration had also a profound effect on color and antioxidant properties of the beads. As the concentration of MLE increased, the beads appeared lighter and their chroma increased. The radical scavenging activity was ameliorated by the MLE concentration increase for samples hardened for 8 and 20 min, whereas it was unaffected for those at 2 min. The hardening time on the contrary did not affect the inhibition of DPPH• values, regardless of the amount of extract added.

Glycerol and Glycerol-Based Deep Eutectic Mixtures as Emerging Green Solvents for Polyphenol Extraction: The Evidence So Far

The acknowledgement that uncontrolled and excessive use of fossil resources has become a prime concern with regard to environmental deterioration, has shifted the orientation of economies towards the implementation of sustainable routes of production, through the valorization of biomass. Green chemistry plays a key role in this regard, defining the framework of processes that encompass eco-friendly methodologies, which aim at the development of highly efficient production of numerous bioderived chemicals, with minimum environmental aggravation. One of the major concerns of the chemical industry in establishing sustainable routes of production, is the replacement of fossil-derived, volatile solvents, with bio-based benign ones, with low vapor pressure, recyclability, low or no toxicity, availability and low cost. Glycerol is a natural substance, inexpensive and non-toxic, and it is a principal by-product of biodiesel industry resulting from the transesterification process. The ever-growing market of biodiesel has created a significant surplus of glycerol production, resulting in a concomitant drop of its price. Thus, glycerol has become a highly available, low-cost liquid, and over the past decade its use as an alternative solvent has been gaining unprecedented attention. This review summarizes the utilization of glycerol and glycerol-based deep eutectic mixtures as emerging solvents with outstanding prospect in bioactive polyphenol extraction.

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

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

Batch Stirred-Tank Green Extraction of Salvia fruticosa Mill. Polyphenols Using Newly Designed Citrate-Based Deep Eutectic Solvents and Ultrasonication Pretreatment

A series of citrate salts were tested as hydrogen bond acceptors to synthesize deep eutectic solvents (DES) based on lactic acid and glycerol, used as hydrogen bond donors. The DES produced were then screened to identify the highest performing system for the effective extraction of polyphenolic phytochemicals from the medicinal plant Salvia fruticosa Mill. (Greek sage). The most efficacious DES was the one composed of lactic acid and sodium citrate dibasic, at a molar ratio of 15:1 (LA-SCDB15). Furthermore, for the first time there has been evidence concerning DES pH and extraction efficiency. Using this solvent, a batch, stirred-tank extraction process was developed, by employing ultrasonication pretreatment and response surface methodology. The optimal settings determined were stirring speed 900 rpm, proportion of DES/water 77% (w/v), and ultrasonication pretreatment time 15 min. By adjusting these optimal settings, the predicted maximum total polyphenol yield was calculated to be 79.93 ± 1.92 mg gallic acid equivalents g−1 dry mass. The examination of temperature effects demonstrated that the batch, stirred-tank extraction stage was very energy-efficient, with a barrier of 7.64 kJ mol−1. Comparison of the extraction of Salvia fruticosa polyphenols with other green processes previously developed, illustrated the high extraction capacity of LA-SCDB15. The major polyphenols identified in the extracts produced under optimized settings were chlorogenic acid, luteolin 7-O-glucuronide and rosmarinic acid.

Hydroglycerolic Solvent and Ultrasonication Pretreatment: A Green Blend for High-Efficiency Extraction of Salvia fruticosa Polyphenols

Salvia fruticosa Miller, also known as Cretan or Greek sage, is a medicinal plant with significant biological properties, which are largely ascribed to its polyphenolic composition, but there is to-date a scarcity of green and sustainable processes for efficient polyphenol extraction from this plant. The objective of this study was the implementation of an extraction process that would combine a green solvent based on glycerol, a biodiesel industry by-product, and ultrasonication pretreatment. Ultrasonication for 40 min followed by stirred-tank extraction was shown to provide significantly higher total polyphenol yield than mere stirred-tank extraction, while kinetics indicated 50 °C as the most favorable temperature, with the yield being 92 mg gallic acid equivalents (GAE) per g dry mass. Comparison of this method with a previously developed one that used methyl β-cyclodextrin revealed that the extracts obtained had similar antioxidant activity, and yield in major polyphenols including luteolin 7-O-glucuronide and rosmarinic acid was virtually equal. The current process is proposed as a sustainable and effective methodology for the generation of polyphenol-enriched extracts from S. fruticosa, which could be used as effective food antioxidants/antimicrobials and/or cosmetic constituents.

Development of a Low-Temperature and High-Performance Green Extraction Process for the Recovery of Polyphenolic Phytochemicals from Waste Potato Peels Using Hydroxypropyl β-Cyclodextrin

Potato peels (PP) are a major agri-food side-stream originating from potato processing, but to date, their green valorization as a bioresource of antioxidant polyphenols is limited to extraction processes involving mainly water/ethanol-based solvents, whereas other eco-friendly methodologies are scarce. This study aimed at developing a simple, straight-forward and green extraction methodology to effectively recover PP polyphenols, using hydroxypropyl β-cyclodextrin (HP-β-CD). After an initial assay to identify the optimal HP-β-CD concentration that would provide increased extraction yield, optimization based on response surface methodology enabled maximization of the extraction performance, providing a total polyphenol yield of 17.27 ± 0.93 mg chlorogenic acid equivalent g−1 dry mass, at 30 °C. Testing of temperatures higher than 30 °C and up to 80 °C did not favor higher yields. The extracts obtained with HP-β-CD were slightly richer in polyphenols than extracts prepared with conventional solvents, such as aqueous ethanol and methanol, displaying similar antioxidant characteristics. The major polyphenols that could be identified in the extracts were neochlorogenic, chlorogenic, caffeic and ferulic acids. The outcome of this study demonstrated that HP-β-CD may be used as a highly effective green means of recovering PP polyphenols, at near-ambient temperature.

Green Valorization of Olive Leaves to Produce Polyphenol-Enriched Extracts Using an Environmentally Benign Deep Eutectic Solvent

Olive leaves (OLL) are considered to be a highly appreciated bioresource of bioactive polyphenolic phytochemicals, embracing several different structures. However, extraction processes based on deep eutectic solvents (DES) are very limited despite the wide range of techniques developed for the efficient recovery of polyphenols. This study had as objective the development of a simple, green, high-performance extraction methodology for OLL polyphenols, using a recently reported effective DES, composed of L-lactic acid and glycine. Initially, a screening was performed to select the most appropriate L-lactic/glycine molar ratio and process optimization was then carried out with response surface methodology. The optimized process variable values were DES/water (78% w/v), liquid-to-solid ratio of 36 mL g−1, and stirring speed of 500 rounds per minute, and the total polyphenol yield amounted to 97.53 ± 3.54 mg gallic acid equivalents per g dry matter. Extraction with DES at 80 °C did not significantly increase the total polyphenol yield, but it did enhance the total flavonoid yield and antioxidant activity. High-performance liquid chromatography analyses revealed that extraction with the DES resulted in extended oleuropein hydrolysis, to the favor of hydroxytyrosol formation. This finding might have a prospect in using properly tuned DES for polyphenol modification with improved bioactivities.

A Green Extraction Process for Polyphenols from Elderberry (Sambucus nigra) Flowers Using Deep Eutectic Solvent and Ultrasound-Assisted Pretreatment

Sambucus nigra flowers, known as elderberry flowers (EBF), are a plant tissue rich in polyphenolic phytochemicals with important bioactivities. However, there are few studies dealing with the production of polyphenol-containing EBF extracts. The objective of the investigation presented herein was the development of a high-performance green extraction methodology, to generate EBF extracts enriched in polyphenolic substances, using an efficient deep eutectic solvent, combined with ultrasonication pretreatment. The DES was composed of L-lactic acid (hydrogen bond donor—HBD) and glycine (hydrogen bond acceptor—HBA) and, after an initial screening to properly regulate HBD/HBA ratio, the extraction was optimized by deploying response surface methodology. Under the optimized conditions, which were DES/water (85% w/v), liquid-to-solid ratio 60 mL g⁻¹, and stirring speed 200 rounds per minute, the extraction yield in total polyphenols amounted to 121.24 ± 8.77 mg gallic acid equivalents per g dry matter. The integration of ultrasonication prior to the batch stirred-tank extraction boosted polyphenol recovery of up to 174.73 ± 2.62 mg gallic acid equivalents per g dry matter. Liquid chromatography–mass spectrometry analysis showed that the richest EBF extract obtained was dominated by rutin, a di-p-coumaroylquic acid and chlorogenic acid.