Recent advances in the extraction of bioactive compounds with subcritical water: A review

Antioxidant and antimicrobial extracts from grape stalks obtained with subcritical water. Potential use in active food packaging development

In order to valorise winemaking grape stalks, subcritical water extraction at 160 and 180 °C has been carried out to obtain phenolic-rich extracts useful for developing active food packaging materials. Red (R) and white (W) varieties (from Requena, Spain) were used, and thus, four kinds of extracts were obtained. These were characterised as to their composition, thermal stability and antioxidant and antibacterial activity. The extracts were incorporated at 6 wt% into polylactic acid (PLA) films and their effect on the optical and barrier properties of the films and their protective effect against sunflower oil oxidation was analysed. Carbohydrates were the major compounds (25-38%) in the extracts that contained 3.5-6.6% of phenolic compounds, the R extracts being the richest, with higher radical scavenging capacity. Every extract exhibited antibacterial effect against Escherichia coli and Listeria innocua, while PLA films with extracts preserved sunflower oil against oxidation.

Deep eutectic solvents as sustainable extraction media for extraction of polysaccharides from natural sources: Status, challenges and prospects

Deep eutectic solvents (DES) emerge as promising alternatives to conventional solvents, offering outstanding extraction capabilities, low toxicity, eco-friendliness, straightforward synthesis procedures, broad applicability, and impressive recyclability. DES are synthesized by combining two or more components through various synthesis procedures, such as heat-assisted mixing/stirring, grinding, freeze drying, and evaporation. Polysaccharides, as abundant natural materials, are highly valued for their biocompatibility, biodegradability, and sustainability. These versatile biopolymers can be derived from various natural sources such as plants, algae, animals, or microorganisms using diverse extraction techniques. This review explores the synthesis procedures of DES, their physicochemical properties, characterization analysis, and their application in polysaccharide extraction. The extraction optimization strategies, parameters affecting DES-based polysaccharide extraction, and separation mechanisms are comprehensively discussed. Additionally, this review provides insights into recently developed molecular guides for DES screening and the utilization of artificial neural networks for optimizing DES-based extraction processes. DES serve as excellent extraction media for polysaccharides from different sources, preserving their functional features. They are utilized both as extraction solvents and as supporting media to enhance the extraction abilities of other solvents. Continued research aims to improve DES-based extraction methods and achieve selective, energy-efficient processes to meet the demands of this expanding field.

Environmental remediation of emerging contaminants using subcritical water: A review

The continuous rise of emerging contaminants (ECs) in the environment has been a growing concern due to their potentially harmful effects on humans, animals, plants, and aquatic life, even at low concentrations. ECs include human and veterinary pharmaceuticals, hormones, personal care products, pesticides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organic dyes, heavy metals (HMs), and others. The world's growing population contributes to the release of many kinds of chemicals into the environment, which is estimated to be more than 200 billion metric tons annually and results in over 9 million deaths. The removal of these contaminants using conventional physical, chemical, and biological treatments has proven to be ineffective, highlighting the need for simple, effective, inexpesive, practical, and eco-friendly alternatives. Thus, this article discusses the utilization of subcritical water oxidation (SBWO) and subcritical water extraction (SBWE) techniques to remove ECS from the environment. Subcritical water (water below the critical temperature of 374.15 °C and critical pressure of 22.1 Mpa) has emerged as one of the most promising methods for remediation of ECs from the environment due to its non-toxic properties, simplicity and efficiency of application. Furthermore, the impact of temperature, pressure, treatment time, and utilization of chelating agents, organic modifiers, and oxidizing agents in the static and dynamic modes was investigated to establish the best conditions for high ECs removal efficiencies.

Ecological and human health impact assessments based on long-term monitoring of soil PAHs near a coal-fired power plant

The combustion of coal in power plants releases significant amounts of polycyclic aromatic hydrocarbons (PAHs), which are highly toxic and carcinogenic. This study assesses the ecological and human health impacts of PAHs contamination from a coal-fired power plant over 8 years. The monitoring site selection considered the distance from the power plant and the prevailing wind direction in the investigated area. The results reveal that, during the monitoring period, PAH levels increased on average by 43%, 61%, and 37% in the zone of the prevailing wind direction, in the area proximate to the power plant, and the zone distant from it, respectively. The site, which has a radius of 4.5 km in the prevailing wind direction, exhibited the highest ecological and human health impacts. Additionally, a strong correlation was observed between environmental and human health impacts, depending on the distance from the power plant, particularly in areas with the prevailing wind direction. These insights contribute to a comprehensive understanding of the intricate dynamics linking power plant emissions, PAHs contamination, and their far-reaching consequences on the environment and human health.

Characterization of temperature-dependent subcritical water hydrolysis pattern of strong and floury rice cultivars and potential utilizations of their hydrolysates

This study investigated the effects of subcritical water (SW) temperatures on the hydrolysis pattern and characteristics of hydrolysates prepared with strong rice (SR) and floury rice (FR). The characteristics of the hydrolysates were generally dependent on the rice cultivar in the SW temperature range of 150-250 °C, while the cultivar dependence was diminished at temperatures greater than 300 °C. Based on brix and reducing sugar content, an optimal production of rice hydrolysates was obtained at a SW temperature range of 200-250 °C. However, thermal conversion of sugar into acids, 5-hydroxymethylfurfural (HMF) and furfural was manifested at 250 °C. The rice hydrolysates prepared at 250 ∼ 300 °C had the highest antioxidant activity with strong umami intensity, but they suppressed the growth of prebiotics. Therefore, the present study demonstrated that controlling the SW temperature is crucial to improve rice hydrolysis efficiency and to regulate the physiological activity of the hydrolysates.

Comparative Anti-Cancer and Anti-Inflammatory Activities of Essential Oils from the Bark and Flower of Magnolia officinalis Rehd. et Wils

This study was designed to compare the antioxidant, antitumor and anti-inflammatory effects of essential oils from the bark and flower of Magnolia officinalis Rehd. et Wils. Distillation extraction and steam distillation were used to extract EOs from the bark and flower. The results showed that the contents of EOs of SDE-F and SDE-B were much higher than that of SD-F and SD-B. EOs from the bark were rich in eudesmol (especially α-eudesmol) and exhibited a stronger antioxidant effect than the flower. The anti-tumor effects of SD-B and SD-F on HepG2 and MDA-MB-231 cells were better than that of SDE-B and SDE-F. The inhibitory rates of SD-B and SD-F on MDA-MB-231 cells were 59.21% and 48.27%, exceeding that of positive control 5-fluorouracil (47.04%) at 50 μg/mL. All four EOs exhibited excellent anti-inflammatory activities through the regulation of nitric oxide production and pro-inflammation cytokines in LPS-induced RAW 264.7 cells and they also remarkably suppressed the mRNA expressions of nitric oxide synthase, IL-6 and TNF-α at the concentration higher than that of positive control dexamethasone. These results indicated significant differences in the composition, and anti-inflammatory and anti-tumor activities of EOs extracted by different methods and provided a theoretical basis for their development and utilization.

Unveiling the Chemistry of Citrus Peel: Insights into Nutraceutical Potential and Therapeutic Applications

The recent millennium has witnessed a notable shift in consumer focus towards natural products for addressing lifestyle-related disorders, driven by their safety and cost-effectiveness. Nutraceuticals and functional foods play an imperative role by meeting nutritional needs and offering medicinal benefits. With increased scientific knowledge and awareness, the significance of a healthy lifestyle, including diet, in reducing disease risk is widely acknowledged, facilitating access to a diverse and safer diet for longevity. Plant-based foods rich in phytochemicals are increasingly popular and effectively utilized in disease management. Agricultural waste from plant-based foods is being recognized as a valuable source of nutraceuticals for dietary interventions. Citrus peels, known for their diverse flavonoids, are emerging as a promising health-promoting ingredient. Globally, citrus production yields approximately 15 million tons of by-products annually, highlighting the substantial potential for utilizing citrus waste in phyto-therapeutic and nutraceutical applications. Citrus peels are a rich source of flavonoids, with concentrations ranging from 2.5 to 5.5 g/100 g dry weight, depending on the citrus variety. The most abundant flavonoids in citrus peel include hesperidin and naringin, as well as essential oils rich in monoterpenes like limonene. The peel extracts exhibit high antioxidant capacity, with DPPH radical scavenging activities ranging from 70 to 90%, comparable to synthetic antioxidants like BHA and BHT. Additionally, the flavonoids present in citrus peel have been found to have antioxidant properties, which can help reduce oxidative stress by 30% and cardiovascular disease by 25%. Potent anti-inflammatory effects have also been demonstrated, reducing inflammatory markers such as IL-6 and TNF-α by up to 40% in cell culture studies. These findings highlight the potential of citrus peel as a valuable source of nutraceuticals in diet-based therapies.

Insights into Cold Plasma Treatment on the Cereal and Legume Proteins Modification: Principle, Mechanism, and Application

Cereal and legume proteins, pivotal for human health, significantly influence the quality and stability of processed foods. Despite their importance, the inherent limited functional properties of these natural proteins constrain their utility across various sectors, including the food, packaging, and pharmaceutical industries. Enhancing functional attributes of cereal and legume proteins through scientific and technological interventions is essential to broadening their application. Cold plasma (CP) technology, characterized by its non-toxic, non-thermal nature, presents numerous benefits such as low operational temperatures, lack of external chemical reagents, and cost-effectiveness. It holds the promise of improving proteins' functionality while maximally retaining their nutritional content. This review delves into the pros and cons of different cold plasma generation techniques, elucidates the underlying mechanisms of protein modification via CP, and thoroughly examines research on the application of cold plasma in augmenting the functional properties of proteins. The aim is to furnish theoretical foundations for leveraging CP technology in the modification of cereal and legume proteins, thereby enhancing their practical applicability in diverse industries.

Exploring the green frontier: Subcritical water chromatography for sustainable analytical practices

Water in the subcritical state is characterized by properties significantly different from water under standard conditions. These include low viscosity, low surface tension, and a much lower dielectric constant, increasing the solubility of nonpolar substances. For this reason, it can provide an alternative solvent and be used in chromatographic techniques-subcritical water chromatography (SBWC). SBWC appears to be one of the greenest analytical techniques until we unravel chromatography with pure water at room temperature. The versatility of SBWC is explored through its applications in the separation and analysis of a wide range of compounds, including pharmaceuticals, natural products, etc. The use of subcritical water as a mobile phase requires suitable stable stationary phases and special apparatus. Still, it makes it possible to conduct analyses without using organic solvents. When using this technique, it is important to remember that it suits the analysis of thermally stable substances. The following work is a critical review of developments in SBWC.

Advances in encapsulation systems of Antarctic krill oil: From extraction to encapsulation, and future direction

Antarctic krill oil (AKO) is highly sought after by consumers and the food industry due to its richness in a variety of nutrients and physiological activities. However, current extraction methods are not sufficient to better extract AKO and its nutrients, and AKO is susceptible to lipid oxidation during processing and storage, leading to nutrient loss and the formation of off-flavors and toxic compounds. The development of various extraction methods and encapsulation systems for AKO to improve oil yield, nutritional value, antioxidant capacity, and bioavailability has become a research hotspot. This review summarizes the research progress of AKO from extraction to encapsulation system construction. The AKO extraction mechanism, technical parameters, oil yield and composition of solvent extraction, aqueous enzymatic extraction, supercritical/subcritical extraction, and three-liquid-phase salting-out extraction system are described in detail. The principles, choice of emulsifier/wall materials, preparation methods, advantages and disadvantages of four common encapsulation systems for AKO, namely micro/nanoemulsions, microcapsules, liposomes and nanostructured lipid carriers, are summarized. These four encapsulation systems are characterized by high encapsulation efficiency, low production cost, high bioavailability and high antioxidant capacity. Depending on the unique advantages and conditions of different encapsulation methods, as well as consumer demand for health and nutrition, different products can be developed. However, existing AKO encapsulation systems lack relevant studies on digestive absorption and targeted release, and the single product category of commercially available products limits consumer choice. In conjunction with clinical studies of AKO encapsulation systems, the development of encapsulation systems for special populations should be a future research direction.

Valorization of tea waste: Composition, bioactivity, extraction methods, and utilization

Tea is the most consumed beverage worldwide and has many health effects. Although there are many different types of tea, black tea and green tea comprise 98% of total tea production in the world. Tea waste production consists of withering, crushing, fermentation, drying and finally packaging processes. All of the waste generated during this production line is called tea waste. Tea production results in a significant amount of waste that cannot be effectively used for value creation. This waste contains many different components including protein, fiber, caffeine, and polyphenols. Due to its rich composition, it can be revalorized for different purposes. In this study, the general composition and bioactive compounds of tea waste were reviewed. Despite the fact that there have been few studies on the bioactivity of tea waste, those studies have also been discussed. The extraction techniques that are used to separate the compounds in the waste are also covered. It has been indicated that these valuable compounds, which can be separated from tea wastes by extraction methods, have the potential to be used for different purposes, such as biogas production, functional foods, food additives, silages, soluble packaging materials, and adsorbents. Although there are some studies on the revalorization of tea waste, new studies on the extraction of bioactive compounds are necessary to improve its utilization potential.

Green and Efficient Extraction of Phenolic Components from Plants with Supramolecular Solvents: Experimental and Theoretical Studies

The supramolecular solvent (SUPRAS) has garnered significant attention as an innovative, efficient, and environmentally friendly solvent for the effective extraction and separation of bioactive compounds from natural resources. However, research on the use of a SUPRAS for the extraction of phenolic compounds from plants, which are highly valued in food products due to their exceptional antioxidant properties, remains scarce. The present study developed a green, ultra-sound-assisted SUPRAS method for the simultaneous determination of three phenolic acids in Prunella vulgaris using high-performance liquid chromatography (HPLC). The experimental parameters were meticulously optimized. The efficiency and antioxidant properties of the phenolic compounds obtained using different extraction methods were also compared. Under optimal conditions, the extraction efficiency of the SUPRAS, prepared with octanoic acid reverse micelles dispersed in ethanol-water, significantly exceeded that of conventional organic solvents. Moreover, the SUPRAS method demonstrated greater antioxidant capacity. Confocal laser scanning microscopy (CLSM) images revealed the spherical droplet structure of the SUPRAS, characterized by a well-defined circular fluorescence position, which coincided with the position of the phenolic acids. The phenolic acids were encapsulated within the SUPRAS droplets, indicating their efficient extraction capacity. Furthermore, molecular dynamics simulations combined with CLSM supported the proposed method's mechanism and theoretically demonstrated the superior extraction performance of the SUPRAS. In contrast to conventional methods, the higher extraction efficiency of the SUPRAS can be attributed to the larger solvent contact surface area, the formation of more types of hydrogen bonds between the extractants and the supramolecular solvents, and stronger, more stable interaction forces. The results of the theoretical studies corroborate the experimental outcomes.

Comprehensive Assessment of Polysaccharides Extracted from Squash by Subcritical Water under Different Conditions

The effects of subcritical water microenvironment on the physiochemical properties, antioxidant activity and in vitro digestion of polysaccharides (SWESPs) from squash were investigated. After single-factor experiments, twenty samples were successfully prepared at different extraction temperatures (110, 130, 150, 170 and 190 °C) and extraction times (4, 8, 12 and 16 min). Under a low temperature environment, the whole process was mainly based on the extraction of SWESP. At this time, the color of SWESP was white or light gray and the molecular mass was high. When the temperature was 150 °C, since the extraction and degradation of SWESP reached equilibrium, the maximum extraction rate (18.67%) was reached at 150 °C (12 min). Compared with traditional methods, the yield of squash SWESP extracted by subcritical water was 3-4 times higher and less time consuming. Under high temperature conditions, SWESPs were degraded and their antioxidant capacity and viscosity were reduced. Meanwhile, Maillard and caramelization reactions turned the SWESPs yellow-brown and produced harmful substances. In addition, different SWESPs had different effects on in vitro digestion. In brief, SWESPs prepared under different conditions have different structures and physicochemical properties, allowing the obtainment of the required polysaccharide. Our results show that squash polysaccharides prepared in different subcritical water states had good development potential and application in the food industry.

Using Subcritical Water to Obtain Polyphenol-Rich Extracts with Antimicrobial Properties

The use of green extraction methods that meet the criteria of sustainable and environmentally friendly technologies has been increasing in recent decades due to their many benefits. In this respect, extracts obtained using subcritical water are also gaining increased attention because of their potential antioxidant and antimicrobial properties. Their antimicrobial activity is mainly due to the presence of various polyphenolic compounds. Although the exact mechanism of the antibacterial action of polyphenolic compounds has not yet been fully investigated and described, polyphenols are known to affect the bacterial cell at several cellular levels; among other things, they cause changes and ruptures in the cell membranes of the bacterial cell, affect the inactivation of bacterial enzymes and damage bacterial DNA. The difference in the strength of the antimicrobial activity of the extracts is most likely a result of differences in their lipophilicity and in the number and position of hydroxyl groups and double bonds in the chemical structure of polyphenols. By changing the extraction conditions, especially the temperature, during subcritical water extraction, we affect the solubility of the compounds we want to extract. In general, as the temperature increases, the solubility of polyphenolic compounds also increases, and the reduction of the surface tension of subcritical water at higher temperatures also enables faster dissolution of polyphenolic compounds. Different bacterial strains have different sensitivity to different extracts. However, extracts obtained with subcritical water extraction demonstrate strong antimicrobial activity compared to extracts obtained with conventional methods.

Subcritical water treatment to modify insoluble dietary fibers from brewer's spent grain for improved functionality and gut fermentability

Lactic acid (LA)-assisted subcritical water treatment (SWT) was applied to modify the insoluble dietary fiber (IDF) from brewer's spent grain (BSG) for enhancing its functionality and gut fermentability. Modified IDFs were thoroughly characterized for their chemical and structural properties. The results revealed that increasing the treatment temperature and LA concentration reduced hemicellulose content in IDFs from 38.4 % to 0.7 %, alongside a decreased yield (84.8 %-51.4 %), reduced particle size (519.8-288.6 μm), and more porous structure of IDFs. These modifications were linked to improved functionalities, evidenced by the highest water and oil holding capacity increasing by 36 % and 67 %, respectively. Remarkably, the highest glucose adsorption capacity increased by 6.5 folds. Notably, modified IDFs exhibited slower in-vitro fermentation, elevated short-chain fatty acids (SCFAs) production, and a higher proportion of butyrate in SCFAs. These findings highlight the potential of LA-assisted SWT in transforming BSG-derived IDF into a valuable functional food ingredient.

Effects of Different Solvents on the Total Phenol Content, Total Flavonoid Content, Antioxidant, and Antifungal Activities of Micromeria graeca L. from Middle Atlas of Morocco

Micromeria graeca L. is a dense chemical source of bioactive compounds such as phenolic compounds, which have various health-related properties. The current study aimed to investigate the impact of different extractor solvents on phenol and flavonoid contents, as well as the antioxidant and antifungal activities of different extracts. Initially, three extractor solvents (methanol, ethyl acetate, and water) were used to prepare the Soxhlet extracts, which were then examined for their polyphenolic content, flavonoid content, and antioxidant potential using three complementary assays (DPPH, FRAP, and TAC). The antifungal capacity against the two fungal strains (Candida albicans and Aspergillus niger) was performed using the method of diffusion on disc. The dosage of phytochemical compounds revealed that the highest values were established in water extract with values of 360 ± 22.1 mg GAE/g dry weight plant and 81.3 ± 21.2 mg RE/g dry weight plant for TPC and TFC, respectively. In addition, the strongest antioxidant activity measured by DPPH and FRAP assays was established in water extract with IC50 values of 0.33 ± 0.23 and 0.23 ± 0.12 mg/mL, respectively, while the methanol extract showed the best antioxidant activity as measured by TAC with an IC50 of 483 ± 17.6 mg GAEq/g dry weight plant. The water extract recorded the most important antifungal activity against Candida albicans with an inhibition zone of 16 ± 1.6 mm and MFC = 500 μg/mL, whereas ethyl acetate extract showed the lowest activity against both studied fungi strains. Micromeria graeca L. contains considerable amounts of bioactive contents with high antioxidant and antifungal potentials, which may make it a promising source of antioxidants and natural antifungal agents.

Improved energy recovery from yard waste by water-starved hydrothermal treatment: Effects of process water and pressure

This study investigated the feasibility of a high-loading process with less water consumption for the valorization of wet biomass waste through hydrothermal carbonization (HTC) with and without N2 pressurization from the views of water saving, carbon utilization, and energy recovery. The results revealed that reducing the liquid-to-solid ratio from 10 to 2.5 significantly improved carbon storage in hydrochar due to preferential carbon sequestration as the solid phase (59.9%) instead of being lost in the liquid phase (∼10%). The pressurized HTC process resulted in a higher stability hydrochar through the devolatilization of secondary char that was less stable, yet resulted in ∼10% 15% more carbon transformation to the gas phase. A cost-benefit analysis further demonstrated the potential of the high-loading HTC process for enhancing energy recovery while minimizing energy consumption during hydrochar production from high-moisture yard waste.

Blueberry Pruning Wastes: From an Undervalued Agricultural Residue to a Safe and Valuable Source of Antioxidant Compounds for the Food Industry

Blueberry fruits have been widely explored for their rich composition of bioactive compounds with recognized health benefits. In contrast, blueberry pruning waste (BPW), generated during the pruning stages of blueberries, has been typically overlooked, even though it can represent a potential source of natural antioxidants. This study aims to characterize the value-added compounds extracted from BPW using green techniques, namely microwave-assisted and subcritical water extraction. The total phenolic content ranged from 157 ± 5 to 335 ± 12 mg GAE/g dw, while the radical scavenging activity determined by a DPPH assay varied from 223 ± 21 to 453 ± 21 mg Trolox equivalents/g dw. Additionally, to ensure the safe application of BPW and its extracts, a screening of pesticides and several environmental contaminants was conducted. Chlorpyrifos-methyl was quantified at a concentration of 4.27 µg/kg in a Bluecrop variety collected in 2019; however, none of the studied compounds were found in the extracts. Despite the presence of a pesticide, this level was below the maximum residue limits for blueberry crops. The results of this study demonstrated the potential of this agro-industrial residue as a natural source of bioactive compounds with high antioxidant activity for food industry applications.

A Comprehensive Review on Deep Eutectic Solvents and Its Use to Extract Bioactive Compounds of Pharmaceutical Interest

The extraction of bioactive compounds of pharmaceutical interest from natural sources has been significantly explored in recent decades. However, the extraction techniques used were not very efficient in terms of time and energy consumption; additionally, the solvents used for the extraction were harmful for the environment. To improve the environmental impact of the extractions and at the same time increase the extraction yields, several new extraction techniques were developed. Among the most used ones are ultrasound-assisted extraction and microwave-assisted extraction. These extraction techniques increased the yield and selectivity of the extraction in a smaller amount of time with a decrease in energy consumption. Nevertheless, a high volume of organic solvents was still used for the extraction, causing a subsequent environmental problem. Neoteric solvents appeared as green alternatives to organic solvents. Among the neoteric solvents, deep eutectic solvents were evidenced to be one of the best alternatives to organic solvents due to their intrinsic characteristics. These solvents are considered green solvents because they are made up of natural compounds such as sugars, amino acids, and carboxylic acids having low toxicity and high degradability. In addition, they are simple to prepare, with an atomic economy of 100%, with attractive physicochemical properties. Furthermore, the huge number of compounds that can be used to synthesize these solvents make them very useful in the extraction of bioactive compounds since they can be tailored to be selective towards a specific component or class of components. The main aim of this paper is to give a comprehensive review which describes the main properties, characteristics, and production methods of deep eutectic solvents as well as its application to extract from natural sources bioactive compounds with pharmaceutical interest. Additionally, an overview of the more recent and sustainable extraction techniques is also given.

A Review: Subcritical Water Extraction of Organic Pollutants from Environmental Matrices

Most organic pollutants are serious environmental concerns globally due to their resistance to biological, chemical, and photolytic degradation. The vast array of uses of organic compounds in daily life causes a massive annual release of these substances into the air, water, and soil. Typical examples of these substances include pesticides, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). Since they are persistent and hazardous in the environment, as well as bio-accumulative, sensitive and efficient extraction and detection techniques are required to estimate the level of pollution and assess the ecological consequences. A wide variety of extraction methods, including pressurized liquid extraction, microwave-assisted extraction, supercritical fluid extraction, and subcritical water extraction, have been recently used for the extraction of organic pollutants from the environment. However, subcritical water has proven to be the most effective approach for the extraction of a wide range of organic pollutants from the environment. In this review article, we provide a brief overview of the subcritical water extraction technique and its application to the extraction of PAHs, PCBs, pesticides, pharmaceuticals, and others form environmental matrices. Furthermore, we briefly discuss the influence of key extraction parameters, such as extraction time, pressure, and temperature, on extraction efficiency and recovery.

Subcritical Water Extraction to Valorize Grape Biomass-A Step Closer to Circular Economy

With the increase in the world population, the overexploitation of the planet's natural resources is becoming a worldwide concern. Changes in the way humankind thinks about production and consumption must be undertaken to protect our planet and our way of living. For this change to occur, sustainable development together with a circular economic approach and responsible consumption are key points. Agriculture activities are responsible for more than 10% of the greenhouse gas emissions; moreover, by 2050, it is expected that food production will increase by 60%. The valorization of food waste is therefore of high importance to decrease the environmental footprint of agricultural activities. Fruits and vegetables are wildly consumed worldwide, and grapes are one of the main producers of greenhouse gases. Grape biomass is rich in bioactive compounds that can be used for the food, pharmaceutical and cosmetic industries, and their extraction from this food residue has been the target of several studies. Among the extraction techniques used for the recovery of bioactive compounds from food waste, subcritical water extraction (SWE) has been the least explored. SWE has several advantages over other extraction techniques such as microwave and ultrasound extraction, allowing high yields with the use of only water as the solvent. Therefore, it can be considered a green extraction method following two of the principles of green chemistry: the use of less hazardous synthesis (principle number 3) and the use of safer solvents and auxiliaries (principle number 5). In addition, two of the green extraction principles for natural products are also followed: the use of alternative solvents or water (principle number 2) and the use of a reduced, robust, controlled and safe unit operation (principle number 5). This review is an overview of the extraction process using the SWE of grape biomass in a perspective of the circular economy through valorization of the bioactive compounds extracted. Future perspectives applied to the SWE are also discussed, as well as its ability to be a green extraction technique.

Dynamic high pressure microfluidization-assisted extraction of plant active ingredients: a novel approach

The extraction method has a great influence on the yield, quality, chemical structure, and biological activities of active ingredients. Safe and efficient extraction of active ingredients is one of the important problems facing the food and pharmaceutical industry. As a pretreatment approach for the extraction of active ingredients, dynamic high pressure microfluidization (DHPM) is a promising strategy that can not only effectively increase the yield of active ingredients but also strengthen the bioactivities of active ingredients, and take the advantages of mild operating temperature and environmental friendliness. In this review, the research progress of DHPM-assisted extraction of active ingredients from plant materials in recent ten years is overviewed. The DHPM equipment, strengthening mechanism, operating procedure, critical factors and application of DHPM-assisted extraction are introduced in detail, together with the advantages and disadvantages. Furthermore, its future development trend is discussed at the end. DHPM-assisted extraction is considered as the ideal technique of better homogenization effects, less solvent consumption, more reliable operation, and so on, making it a promising method to acquire active ingredients efficiently. Therefore, this technique is worthy of further theoretical research and experimental operation.

Subcritical Water Extraction for Valorisation of Almond Skin from Almond Industrial Processing

Almond skin (AS) is an agro-industrial residue from almond processing that has a high potential for valorisation. In this study, subcritical water extraction (SWE) was applied at two temperatures (160 and 180 °C) to obtain phenolic-rich extracts (water-soluble fraction) and cellulose fibres (insoluble fraction) from AS. The extraction conditions affected the composition and properties of both valorised fractions. The dry extracts obtained at 180 °C were richer in phenolics (161 vs. 101 mg GAE. g-1 defatted almond skin (DAS)), with greater antioxidant potential (1.063 vs. 1.490 mg DAS.mg-1 DPPH) and showed greater antibacterial effect (lower MIC values) against L. innocua (34 vs. 90 mg·mL-1) and E. coli (48 vs. 90 mg·mL-1) than those obtained at 160 °C, despite the lower total solid yield (21 vs. 29%) obtained in the SWE process. The purification of cellulose from the SWE residues, using hydrogen peroxide (H2O2), revealed that AS is not a good source of cellulose material since the bleached fractions showed low yields (20-21%) and low cellulose purity (40-50%), even after four bleaching cycles (1 h) at pH 12 and 8% H2O2. Nevertheless, the application of a green, scalable, and toxic solvent-free SWE process was highly useful for obtaining AS bioactive extracts for different food, cosmetic, or pharmaceutical applications.

Comparison of the effect of extraction methods on waste cotton (Gossypium hirsutum L.) flowers: metabolic profile, bioactive components, antioxidant, and α-amylase inhibition

BACKGROUND

Waste cotton flowers, as a by-product of cotton cultivation, are enriched with bioactive substances that render them a promising natural source of health-promoting benefits. In this study, ultrasound-assisted extraction (UAE), subcritical water extraction (SWE), and conventional extraction (CE) approaches were applied to extract bioactive compounds from waste cotton flowers, and the metabolic profiles, bioactive components, antioxidants, and α-amylase inhibition of different extractions were systematically analyzed and compared.

RESULTS

It was observed that UAE and CE extracts had similar metabolic profiles compared with SWE. The flavonoids and amino acids and derivatives were more prone to be extracted by UAE and CE, whereas phenolic acids tended to accumulate in SWE extract. The UAE extract had the highest amounts of total polyphenols (214.07 mg gallic acid equivalents per gram dry weight) and flavonoids (33.23 mg rutin equivalents per gram dry weight) as well as the strongest inhibition on oxidation (IC50  = 10.80 μg mL-1 ) and α-amylase activity (IC50  = 0.62 mg mL-1 ), indicating that chemical composition was closely related to biological activity. Additionally, microstructures and thermal behaviors of the extracts were investigated and highlighted the ability of UAE.

CONCLUSION

Overall, it can be concluded that UAE is an efficient, green, and economical extraction method to produce bioactive compounds from cotton flowers, and the UAE extracts could be used in food and medicine industries because of their high antioxidant and α-amylase inhibitory activity. This study provides a scientific basis for the development and comprehensive utilization of cotton by-products. © 2023 Society of Chemical Industry.

Recovery of Phenolic Compounds from Jackfruit Seeds Using Subcritical Water Extraction

Jackfruit is one of the major fruits cultivated in many Asian countries. Jackfruit seeds are generally disposed of into the environment, which causes an environmental concern that leads to biowaste accumulation. The seeds have excellent nutritional value, such as carbohydrates, protein, fats, minerals, and bioactive compounds. Bioactive compounds, such as phenolic, can be recovered from jackfruit seeds that could add value to the food and pharmaceutical industry. Thus, this study focused on utilizing subcritical water to extract the phenolic compounds from jackfruit seeds and correlate them with antioxidant activity (AA). The extraction of phenolic compounds was studied at different temperatures and extraction times. The highest total phenolic compounds (TPC) and AA were obtained by treating the jackfruit seed powder at 210 °C, 30 min, and 15% solid loading under subcritical water extraction (SWE) with 1.84 mg GAE/100 g (TPC) and 86% (AA). High correlation between the extracted TPC and AA of the jackfruit seed extracts was obtained (R2 = 0.96), indicating a significant positive relationship between TPC and AA. A higher amount of TPC was obtained via SWE as compared to Soxhlet extraction (1 h:0.53 mg GAE/100 g and 4 h:1.20 mg GAE/100 g). More pores were detected on the surface of the sample treated by SWE than using Soxhlet extraction. Thus, jackfruit seed extracts can be potentially beneficial in the fortification of fermented dairy or meat products.

Advance in Morchella sp. polysaccharides: Isolation, structural characterization and structure-activity relationship: A review

Morchella sp. is a kind of precious medicinal and edible fungus with a unique flavor and is rich in various amino acids and organic germanium needed by the human body. Most notably, Morchella sp. polysaccharides have attracted widespread attention due to their significant bioactivity in recent years. At present, extensive studies have been carried out on the extraction methods, structural characterization and activity evaluation of Morchella sp. polysaccharides, which provides a good theoretical basis for its further development and application. However, the systematic summary of the related research of Morchella sp. polysaccharides has not been reported yet. Therefore, this review mainly focused on the isolation and purification methods, structural characterization, biological activities and structure-activity relationship of Morchella sp. polysaccharides. This work will help to have a better in-depth understanding of Morchella sp. polysaccharides and provide a scientific basis and direct reference for more scientific and rational applications.

A Comprehensive Review on Bioactive Compounds Found in Caesalpinia sappan

Sappan wood (Caesalpinia sappan) is a tropical hardwood tree found in Southeast Asia. Sappan wood contains a water-soluble compound, which imparts a red color named brazilin. Sappan wood is utilized to produce dye for fabric and coloring agents for food and beverages, such as wine and meat. As a valuable medicinal plant, the tree is also known for its antioxidant, anti-inflammatory, and anticancer properties. It has been observed that sappan wood contains various bioactive compounds, including brazilin, brazilein, sappan chalcone, and protosappanin A. It has also been discovered that these substances have various health advantages; they lower inflammation, enhance blood circulation, and are anti-oxidative in nature. Sappan wood has been used as a medicine to address a range of illnesses, such as gastrointestinal problems, respiratory infections, and skin conditions. Studies have also suggested that sappan wood may have anticarcinogenic potential as it possesses cytotoxic activity against cancer cells. Based on this, the present review emphasized the different medicinal properties, the role of phytochemicals, their health benefits, and several food and nonfood applications of sappan wood. Overall, sappan wood has demonstrated promising medicinal properties and is an important resource in traditional medicine. The present review has explored the potential role of sappan wood as an essential source of bioactive compounds for drug development.

Sustainable Isolation of Bioactive Compounds and Proteins from Plant-Based Food (and Byproducts)

Plant-based food produces significantly less greenhouse gases, and due to its wealth of bioactive components and/or plant-based protein, it becomes an alternative in a sustainable food system. However, the processing and production of products from plant sources creates byproducts, which can be waste or a source of useful substances that can be reused. The waste produced during the production and processing of food is essentially nutrient- and energy-rich, and it is recognized as an excellent source of secondary raw materials that could be repurposed in the process of manufacturing and preparing food, or as feed for livestock. This review offers an overview of the sources and techniques of the sustainable isolation of bioactive substances and proteins from various sources that might represent waste in the preparation or production of food of plant origin. The aim is to uncover novel approaches to use waste and byproducts from the process of making food to provide this waste food an additional benefit, not forgetting the expectations of the end user, the consumer. For the successful isolation of bioactive ingredients and proteins from food of plant origin, it is crucial to develop more eco-friendly and efficient extraction techniques with a low CO2 footprint while considering the economic aspects.

Optimizing the Production of Antioxidant and Antibacterial Alkaloids from Macleaya cordata by Subcritical Water Extraction Technology

In this work, the subcritical water extraction technology was used to extract alkaloids from Macleaya cordata, and the effects of extraction temperature and time on its yield were investigated to find the best extraction conditions. Moreover, the antioxidant capacity and antibacterial activity of Macleaya cordata extract were studied. Furthermore, through the single-factor method, it was found that properly increasing the extraction temperature and prolonging the extraction time was conducive to increasing alkaloid yield. Still, a considerable amount of alkaloids might be decomposed by heat, resulting in a decrease in their yield. The results showed that the optimal extraction temperature of alkaloids from Macleaya cordata with subcritical water is 190 °C, the time is 45 min, and the corresponding maximum yield is 35.19±0.12 mg/g (sanguinarine equivalent in raw materials). In addition, the antioxidation and bacteriostasis abilities of subcritical water extract are better than those of traditional hot water extract, indicating that it is a feasible method to extract alkaloids from Macleaya cordata with subcritical water.

Ultrasonic-assisted extraction for phenolic compounds and antioxidant activity of Moroccan Retama sphaerocarpa L. leaves: Simultaneous optimization by response surface methodology and characterization by HPLC/ESI-MS analysis

This study was designed to optimize the ultrasound-assisted extraction of phenolic compounds and the antioxidant activity of Moroccan Retama sphaerocarpa extracts using response surface methodology (RSM). A central composite design has been conducted to investigate the effects of three factors: extraction period (X₁), solvent concentration (X₂), and solvent-to-material ratio (X₃) on extraction yield, total phenolic content (TPC), flavonoids content (TFC), and antioxidant activity. The obtained results showed that the experimental values agreed with the predicted ones, confirming the capacity of the used model for optimizing the extraction conditions. The best extraction conditions for the simultaneous optimization were an extraction time of 38 min, a solvent concentration of 58%, and a solvent-to-material ratio of 30 mL/g. Under these conditions, the optimized values of yield, TPC, TFC, and DPPH-radical scavenging activity (DPPH_IC50) were 18.91%, 154.09 mg GAE/g, 23.76 mg QE/g, and 122.47 μg/mL, respectively. The further HPLC/ESI-MS analysis of the obtained optimized extract revealed the presence of 14 phenolic compounds with piscidic acid, vitexin, and quinic acid as major compounds. These research findings indicate promising applications for efficiently extracting polyphenolic antioxidants, especially in the food industry.

Exploring Bioactive Compounds in Brown Seaweeds Using Subcritical Water: A Comprehensive Analysis

In this study, we characterized the bioactive properties of three important brown seaweed species, Sargassum thunbergii, Undaria pinnatifida, and Saccharina japonica, by subcritical water extraction (SWE), as these species are well known for their beneficial health effects. Their physiochemical properties, including potential antioxidant, antihypertensive, and α-glucosidase inhibitory activity, and the antibacterial activity of the hydroysates were also analyzed. The highest total phlorotannin, total sugar content, and reducing sugar content in the S. thunbergii hydrolysates were 38.82 ± 0.17 mg PGE/g, 116.66 ± 0.19 mg glucose/g dry sample, and 53.27 ± 1.57 mg glucose/g dry sample, respectively. The highest ABTS⁺ and DPPH antioxidant activities were obtained in the S. japonica hydrolysates (124.77 ± 2.47 and 46.35 ± 0.01 mg Trolox equivalent/g, respectively) and the highest FRAP activity was obtained in the S. thunbergii hydrolysates (34.47 ± 0.49 mg Trolox equivalent/g seaweed). In addition, the seaweed extracts showed antihypertensive (≤59.77 ± 0.14%) and α-glucosidase inhibitory activity (≤68.05 ± 1.15%), as well as activity against foodborne pathogens. The present findings provide evidence of the biological activity of brown seaweed extracts for potential application in the food, pharmaceutical, and cosmetic sectors.

Protein recovery from brewery solid wastes

Brewing produces significant amounts of solid waste during the process: spent cereals (BSG), hops and spent yeast (BSY). These residues are sustainable sources of valuable nutrients and functional compounds like proteins, polyphenols, and polysaccharides. This review describes the three solid wastes and the different extraction techniques for protein recovery. The protein obtained can be used as a new source of non-animal protein or as a functional and bioactive ingredient. Particular attention was given to methods using conventional technologies (alkaline and ethanolic extraction) and more innovative approaches (enzymes, microwaves, ultrasound, pressurized liquids and sub-critical water extraction). Although the BSG is used in some industrial applications, studies in operating conditions, cost, energy efficiency, and product performance are still required to consolidate these solid wastes as a source of non-animal protein. The application of proteins is also an important question when choosing the extraction method.

Antioxidant and Sensory Properties of Raw and Cooked Pork Meat Burgers Formulated with Extract from Non-Compliant Green Coffee Beans

The effects of polyphenol-rich extract obtained from non-compliant defatted green coffee beans (dGCBs) on physicochemical and antioxidant properties, as well as on the sensory profile of vacuum-packed pork burgers stored at 4 °C for 14 days and after cooking were assessed. The dGCB extract obtained by means of supercritical water extraction was analyzed for its polyphenol profile, total phenolic content, radical scavenging, and ferric-reducing antioxidant activities (DPPH and FRAP), Fe2+-chelating capacity, and total iron. The most abundant polyphenol component observed in the dGCB extract was chlorogenic acid, and the alkaloid caffeine was also present. This extract showed antioxidant properties. Thereafter, five formulations of pork meat burgers with added NaCl (1%) were prepared; one without the antioxidant (negative control, C) and one with the use of a synthetic antioxidant (0.05% ascorbic acid = positive control, A), while the other three were supplemented with a different amount of dGCB extract (P15 = 0.15%; P30 = 0.30%; P60 = 0.60%). The addition of dGCB extract increased the antioxidant activity of the raw and cooked burgers and reduced the lipid oxidation of the cooked burgers (0.47, 0.21, and 0.20 vs. 1.28 and 0.55 mg MDA eq./Kg, for P15, P30, and P60 vs. C and A, respectively). No negative effects were observed on the meat’s color parameters and its stability during refrigerated storage and after cooking, nor on sensory attributes (color and aroma) for the lowest concentration of coffee extract. The results obtained indicate that 0.15% dGCB extract is a promising alternative to commercial synthetic antioxidants to improve the quality of refrigerated pork burgers.

Effect of subcritical water flash release processing on buckwheat flour properties

BACKGROUND

Buckwheat (Fagopyrum esculentum) is rich in bioactive components. However, many of these components are trapped within cellular structures, making them inaccessible. Buckwheat flour was hydrothermally modified using subcritical water coupled with a flash pressure release (SCWF). The effects of the SCWF parameters (120, 140, and 160 °C and hold times of 0, 15, and 30 min) on the flour's structure, physicochemical, and functional properties were studied relative to the raw flour.

RESULTS

Treatment deepened the flour color with increasing processing temperatures and hold times. Starch content remained unchanged though its granular structure was disrupted. SCWF treatments lowered total phenolic content compared with the raw flour, except for 160 °C-30 min, where total phenolic content increased by 12.7%. The corresponding antioxidant activities were found consistent with phenolic content. Soluble and insoluble dietary fiber amounts were not substantially influenced at 120 and 140 °C, whereas treatments at 160 °C (15 and 30 min hold) decreased soluble dietary fiber while increasing insoluble dietary fiber. Protein content increased 70-109% in some treatments, suggesting greater protein accessibility. Water-holding capacity significantly increased for flour treated at 120 °C, whereas only slight improvements occurred at 140 and 160 °C.

CONCLUSIONS

Subcritical water flash processing can modify the compositional and functional properties of buckwheat flour depending on the choice of reaction conditions. Observed changes were consistent with alteration of the flour's cellular structure and allow some components to become more accessible. The resulting SCWF-modified buckwheat flours provide new food ingredients for potential use in ready-to-eat foods and spreads with improved health benefits. Published 2022. This article is a U.S. Government work and is in the public domain in the USA.

Recovery of Anthocyanins from Hibiscus sabdariffa L. Using a Combination of Supercritical Carbon Dioxide Extraction and Subcritical Water Extraction

Anthocyanins are one of the bioactive compounds in roselle that has many medicinal proposes. Anthocyanins are placed in the inner part of the roselle; therefore, combinations of two methods were applied to extract the anthocyanins. The first stage is employing supercritical carbon dioxide (ScCO2) to break the particle surface or outer layer of the roselle based on the total phenolic compounds (TPC) recovery, and the second step was to apply subcritical water extraction (SWE) for the extraction of anthocyanins. The objective is to determine the best conditions to obtain high yields of total anthocyanins compounds (TAC) from the roselle (Hibiscus sabdariffa) by employing a combination of ScCO2 and SWE. The optimal conditions of ScCO2 (first stage) were 19.13 MPa, 60 °C, and 4.31 mL/min, yielding 18.20%, and 80.34 mg/100 g TPC, respectively. The optimum conditions of SWE (second stage) were 9.48 MPa, 137 °C, and 6.14 mL/min, yielding 86.11% and 1224.61 mg/100 g TAC, respectively. The application of integrated ScCO2 and SWE proved successful in achieving high anthocyanins production and yield as compared to previous extraction methods. This approach may be used to extract the roselle with a greater anthocyanin’s concentration than the prior method.

Tuning water chemistry for the recovery of greener products: pragmatic and sustainable approaches

The environmental impact and denaturing propensity of organic solvents in the extraction of plant bioactives pose great challenges in extraction systems. As a result, proactive consideration of procedures and evidence for tuning water properties for better recovery and positive influence on the green synthesis of products become pivotal. The conventional maceration approach takes a longer duration (1-72 h) for product recovery while percolation, distillation, and Soxhlet extractions take about 1 to 6 h. An intensified modern hydro-extraction process was identified for tuning water properties with an appreciable yield similar to organic solvents within 10-15 min. The percentage yield of tuned hydro-solvents achieved close to 90% recovery of active metabolites. The additional advantage of using tuned water over organic solvents is in the preservation of the bio-activities and forestalling the possibility of contamination of the bio-matrices during extractions with an organic solvent. This advantage is based on the fast extraction rate and selectivity of the tuned solvent when compared to the traditional approach. This review uniquely approaches the study of biometabolite recovery through insights from the chemistry of water under different extraction techniques for the very first time. Current challenges and prospects from the study are further presented.

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.

Chemical Composition, Antioxidant Activity and Cytocompatibility of Polyphenolic Compounds Extracted from Food Industry Apple Waste: Potential in Biomedical Application

Apple pomace (AP) from the food industry is a mixture of different fractions containing bioactive polyphenolic compounds. This study provides a systematic approach toward the recovery and evaluation of the physiochemical and biological properties of polyphenolic compounds from AP. We studied subcritical water extraction (SCW) and solvent extraction with ethanol from four different AP fractions of pulp, peel, seed, core, and stem (A), peel (B), seed and core (C), and pulp and peel (D). The subcritical water method at the optimum condition resulted in total polyphenolic compounds (TPC) of 39.08 ± 1.10 mg GAE per g of AP on a dry basis compared to the ethanol extraction with TPC content of 10.78 ± 0.94 mg GAE/g db. Phloridzin, chlorogenic acid, and quercetin were the main identified polyphenolics in the AP fractions using HPLC. DPPH radical scavenging activity of fraction B and subcritical water (SW) extracts showed comparable activity to ascorbic acid while all ethanolic extracts were cytocompatible toward human fibroblast (3T3-L1) and salivary gland acinar cells (NS-SV-AC). Our results indicated that AP is a rich source of polyphenolics with the potential for biomedical applications.

Comparison of Conventional Extraction Techniques with Superheated Steam Distillation on Chemical Characterization and Biological Activities of Syzygium aromaticum L. Essential Oil

Syzygium aromaticum L. is an aromatic plant with a significant amount of essential oil (EO), which is used in food, medicine, for flavoring, and in the fragrance industry. The purpose of this study was to comparatively evaluate the chemical composition, yield, and antioxidant and antifungal activities of Syzygium aromaticum essential oils extracted by the conventional hydro-distillation, steam distillation, and the emerging superheated steam distillation methods. It was noticed that the extraction methods significantly influenced the yield, chemical composition, and antioxidant and antimicrobial activities of essential oils. The maximum yield was obtained using superheated steam distillation, followed by hydro-distillation and steam distillation. The antioxidant potential of EO extracts was evaluated following the scavenging of 2,2-dipenyl-1-picrylhydrazyl radicals, hydrogen peroxide scavenging activity and ferric reducing power assays. Results revealed that EO extracted superheated steam distillation exhibited the highest antioxidant activity. GC-MS analysis depicted eugenol (47.94–26.50%) and caryophyllene (20.24–9.25%) as the major compounds of Syzygium aromaticum EOs. The antimicrobial activity of EO extracts was evaluated, via the resazurin microtiter plate assay, microdilution broth assay, and disc diffusion methods, against normal and food pathogenic bacterial and fungal strains. After comparative evaluation, it was observed that superheated steam extracted EO exhibited the highest antimicrobial potential. Overall, methodical evaluation disclosed that superheated steam distillation is an effective method to extract EOs from plant sources, with greater yield and promising biological activities.

Role of hydrothermal pretreatment towards sustainable biorefinery

Recently, the world is experiencing a shift from petroleum refineries to biorefineries due to fossil fuel depletion and environmental concerns. To achieve sustainable development of biorefineries and other components of the biofuel production process, eco-friendly and cost-effective approaches are necessary. Therefore, lignocellulosic biomass (LCB) must be exploited in biorefineries for the generation of a broad spectrum of products. The complex structure of LCB prevents its direct saccharification by enzymatic means, so pretreatment is necessary. There are several pretreatment technologies for disrupting the lignocellulosic structure, but hydrothermal pretreatment is the leading pretreatment technology for recovering hemicellulose fraction with a low number of inhibitors and an increased amount of cellulose. The severity of hydrothermal pretreatment plays a principal role in affecting cellulose, hemicellulose, and lignin structure. A detailed account of microwave-assisted hydrothermal pretreatment technologies and the cost-effectiveness, eco-friendliness, and upcoming challenges of this technology for commercialization with the probable solution is presented.

Supercritical Carbon Dioxide in Presence of Water for the Valorization of Spent Coffee Grounds: Optimization by Response Surface Methodology and Investigation of Caffeine Extraction Mechanism

Spent coffee grounds are a promising bioresource that naturally contain around 50 wt% moisture which requires, for a valorization, a drying step of high energy and economic costs. However, the natural water in spent coffee grounds could bring new benefits as a co-solvent during the supercritical CO₂ extraction (SC-CO₂). This work reports the influence and optimization of pressure (115.9-284.1 bars), temperature (33.2-66.8 °C), and moisture content (6.4-73.6 wt%) on simultaneous extraction of lipids and polar molecules contained in spent coffee grounds by supercritical CO₂ (SC-CO₂) using Central Composite Rotatable Design and Response Surface Methodology. The results show that for lipids extraction, pressure is the most influent parameter, although the influence of moisture content is statistically negligible. This suggests that water does not act as barrier to CO₂ diffusion in the studied area. However, moisture content is the most influent parameter for polar molecules extraction, composed of 99 wt% of caffeine. Mechanism investigations highlight that H₂O mainly act by (i) breaking caffeine interactions with chlorogenic acids present in spent coffee grounds matrix and (ii) transferring selectively caffeine without chlorogenic acid by liquid/liquid extraction with SC-CO₂. Thus, the experiment for the optimization of lipids and polar molecules extraction is performed at a pressure of 265 bars, a temperature of 55 °C, and a moisture content of 55 wt%.

Salicornia ramosissima: A New Green Cosmetic Ingredient with Promising Skin Effects

This study aims to validate a new cosmetic ingredient from Salicornia ramosissima S J. Woods through in vitro and ex vivo assays. The halophyte extracts were obtained by subcritical water extraction (SWE) at different temperatures (110, 120, 140, 160 and 180 °C). The antioxidant/radical scavenging activities and the phenolic profile were screened for all extracts. The optimal extract was assessed in keratinocytes and fibroblasts, while permeation assays were performed in Franz cells. The inhibitory activity of hyaluronidase and elastase was also evaluated. The sample extracted at 180 °C presented the highest phenolic content (1739.28 mg/100 g of dry weight (dw)). Despite not being efficient in the sequestration of ABTS^•+, this extract scavenged the DPPH^• (IC₅₀ = 824.57 µg/mL). The scavenging capacity of superoxide (O₂^•-) and hypochlorous acid (HOCl) was also considerable (respectively, IC₅₀ = 158.87 µg/mL and IC₅₀ = 5.80 µg/mL). The cell viability assays confirmed the absence of negative effects on keratinocytes, while the fibroblasts' viability slightly decreased. The ex vivo permeation of rutin, quercetin and syringic acid after 24 h was, respectively, 11, 20 and 11%. Additionally, the extract showed a good elastase and hyaluronidase inhibitory activity. The results obtained support the S. ramosissima bioactivity as a cosmetic ingredient.

Optimization of Red Pigment Anthocyanin Recovery from Hibiscus sabdariffa by Subcritical Water Extraction

The optimization of red pigment anthocyanin from roselle (Hibiscus sabdariffa) by subcritical water extraction (SWE) has not been the topic of a scientific investigation. Therefore, the objective of this paper was to establish the optimal parameters for obtaining the maximum yield, total anthocyanin compounds (TAC), total phenolic compounds (TPC), and total flavonoid compounds (TFC) by SWE utilizing a response surface methodology. The optimal conditions were 8.75 MPa, 393.54 K, and 4.89 mL/min, with a yield of 0.69 g/g, TAC of 927.74 mg/100 g, TPC of 39.54 mg/100 g, and TFC of 614.57 mg/100 g. High temperatures and flow rates are favorable for achieving a maximum yield. In contrast, a high temperature is suitable for obtaining high concentrations of anthocyanin, flavonoid, and phenolic compounds. This technique (SWE) recovers anthocyanin at a greater extraction rate than traditional methods; hence, SWE may be substituted for conventional methods for extracting anthocyanin.