Subcritical Water Extraction Research Articles

Isolation, Purification,andCharacterization of Lentinus edodes Polysaccharides Extracted with Subcritical Water Enhanced with Deep Eutectic Solvent.

TheLentinus edodespolysaccharide (LEP) was extracted witha new subcritical water extraction (SWE) enhanced with deep eutectic solvent (DES) methodand then purified with a DEAE-52 cellulose column and a Sephadex G-100 column. Two purifiedpolysaccharides (LEP1 and LEP2) were obtained and their structure, antioxidant activity,and immunomodulatory activitywere analyzed. LEP1 and LEP2 were composed ofmannose, glucose, and galactose with amolar ratio of 1:12.97:7.84 and 1:51.18:5.29, respectively. The molecular weightswere 9.878×104Da and 1.976×104Da, respectively. Interestingly, both LEP1 and LEP2 were mainly composed of→4)-β-D-Glcp-(1→, →6)-β-D-Glcp-(1→and →6)-α-D-Galp-(1→ withdifferentmolar ratio. Besides, both LEP1 and LEP2 hadstrong DPPH free radical scavenging activity and Fe2+ chelating capacity.Moreover, theycould reduce the level of ROS and regulate the activities of MDA, CAT, and SOD in HepG2 cells, demonstrating strong antioxidant activity. Furthermore, both LEP1 and LEP2 could improve the phagocytic capacity, NO release, and the content of IL-6, IL-1β,and TNF-α in RAW264.7 cells, exhibitedsignificant immunostimulatory activity. It wasworth noting that LEP2 exhibitedstronger biological activities than LEP1. Therefore, the SWE enhanced with DESis an ideal method for extracting polysaccharides, whichcan be further applied toextract otherpolysaccharides.

Comparative Analysis of Supercritical Carbon Dioxide and Subcritical Water Extraction for Sabah Coffea Canephora

This work provides a thorough comparative analysis of the green extraction process, viz. supercritical carbon dioxide and subcritical water extraction methods for Sabah Coffea canephora. Rigorous experiments were conducted using supercritical carbon dioxide (temperature ranging from 40 °C to 80 °C and pressure from 10 to 30 MPa) and subcritical water (temperature ranging from 120 to 180 °C with extraction times from 5 to 15 min). The optimum conditions for supercritical carbon dioxide extraction were obtained at 79 °C and 30 MPa at the maximum extract yield (8.549%), total phenolic content (4.563 mg/g gallic acid equivalent), total flavonoid content (0.763 mg/g quercetin equivalent) and antioxidant activity (63.34%). Meanwhile, subcritical water extraction is the best extraction method for Coffea canephora, which was obtained optimum conditions at 180 °C and 15 min of extraction time with a maximum extract yield of 44.477%, total phenolic content of 6.481 mg/g gallic acid equivalent, total flavonoid content of 13.816 mg/g quercetin equivalent and 77.586% of antioxidant activity. In conclusion, this understanding contributes to developing optimized conditions for green extraction methods, expanding the potential applications of Sabah Coffea canephora in industries, including pharmaceuticals and functional foods.

Enhanced apigenin yield from parsley via synergistic subcritical-water extraction with pulsed electric field and intense pulsed light pretreatments

Enhanced apigenin yield from parsley via synergistic subcritical-water extraction with pulsed electric field and intense pulsed light pretreatments

Exploring Hyaluronidase and Alpha-Glucosidase Inhibition Activities of the Hydrothermal Extract of Coffee Silverskin Obtained from a Central Composite Design

Coffee silverskin (CS), the main by-product of coffee roasting production, contains various valuable bioactive compounds in its chemical compositions. Hydrothermal water extraction (HDTE) is one of the promising techniques for valorizing the organic fraction of CS into functional bioactive ingredients, which can be further exploited in various applications. This study aimed to evaluate the hyaluronidase and α-glucosidase inhibition activities of the CS extracts obtained under optimized water extraction conditions. Process optimization was performed using central composite design response surface methodology (CCD-RSM) with a broader range of extraction temperatures (25, 137.5, and 250 °C), reaction times (5, 38.5, and 72 min), and solid-to-liquid ratios (1:10, 1:80, and 1:150). The highest yield of 39.62% was obtained at 137.5 °C, with a reaction time of 72 min and an S/L ratio of 1:80. The total caffeoylquinic acid contents (T-CQA) were quantified based on the sum of three major isomers, including 3-CQA, 4-CQA, and 5-CQA. The results revealed that the highest T-CQA (2.76 ± 0.20 mg/g CS) was significantly obtained (p < 0.05) by subcritical water extraction (SWE) at 143.2 °C with an S/L ratio of 1:10 and an extraction time of 10.41 min. At such conditions, the total phenolic content (TPC), antioxidant properties (AP), and caffeine were 96.13 mg gallic acid equivalence per gram (GAE/g) CS, 20.85 ± 0.17 mg Trolox equivalence per gram (TE/g) CS, and 10.84 ± 1.25 mg/g CS, respectively. The 50% inhibition capacity (IC50) of hyaluronidase and α-glucosidase inhibition of the CS extracted were 5.00 mg/mL and 9.00 mg/mL, respectively. Our results supported the potential direct or indirect applications of CS, such as hydrothermal CS extract (HDT-CSE), in functional food or drinks. Repurposing CS residue to manufacture new products can efficiently reduce the amount of organic waste in landfills, thus conserving resources and energy and contributing to a lower overall carbon footprint in coffee production.

Ultrasound Assisted Hybrid Technologies for Extraction of Bioactive Compounds

The sustainable and efficient extraction of bioactive compounds from natural resources offers a promising alternative to synthetic additives and formulations. These compounds including polyphenols, flavonoids and polysaccharides possess antioxidant, antimicrobial and many therapeutic effects rendering them highly demandable by various industries. Conventional extraction methods often exhibit drawbacks such as high energy consumption, excessive solvent usage, prolonged processing times, low extraction yields, and negative environmental impacts. To address these limitations, innovative extraction technologies have emerged, providing more sustainable and efficient solutions. Ultrasound is a promising technology used for extraction of these beneficial compounds with enhanced yield and quality. It can assist various other extraction technologies including microwave assisted extraction, ohmic heating, enzyme extraction, subcritical water extraction and supercritical fluid extraction to obtain high quality extracts. The cavitation and the resulted effects of ultrasound facilitated the cell wall rupture enhancing the mass transfer making the cell structure more accessible by the other extraction technologies for the efficient extraction. This synergistic approach of ultrasound and other mentioned extraction technologies results in increased extraction yields and improved product quality by reducing extraction time, minimizing solvent consumption, and utilizing moderate energy inputs.

Extraction and isomerization of ultraviolet-absorbing substances, saclipins, from an edible cyanobacterium Aphanothece sacrum using subcritical water

The effects of the extraction conditions on the recovery and isomerization of the UV-absorbing saclipins from the edible cyanobacterium Aphanothece sacrum by subcritical water were investigated. The extraction temperature (100–160 ℃) did not affect the extraction efficiency of saclipins, but the pressure (5–15 MPa) had a significant effect. The saclipin B (cis-configuration) ratio in the extract increased with extraction temperature. Since saclipin A (trans-configuration) is predominant in the raw material, it is proposed that thermal-induced cis-isomerization occurs during the extraction process under elevated temperature conditions. Furthermore, we found that extraction with subcritical water resulted in higher extraction and isomerization efficiencies of saclipins than extraction with organic solvents. Extracts obtained by subcritical water extraction (SWE) exhibited antioxidant and anti-elastase activities and the degree of the activities was affected by the extraction temperature (i.e., saclipin isomer ratio). These findings could facilitate the development of sunscreens with enhanced skincare benefits, utilizing naturally-derived bioactive compounds.

Fractionation of Winemaking Grape Stalks by Subcritical Water Extraction to Obtain Added-Value Products.

Grape stalks (GSs) from winemaking were submitted to a green process to valorise its lignocellulosic biomass that applied subcritical water extraction (SWE) at 170 °C and 180 °C to obtain active extracts and cellulose-enriched fractions. The sum of the total phenolic content of the soluble extract and the solid residue fractions from the SWE exceeded that of the GS, which suggests the generation of compounds with antioxidant properties through SWE. All SWE fractions showed high antioxidant power. The increased temperature promoted the extraction of polyphenolic compounds, enhancing the antioxidant power of both extracts and solid residues. These solid residue fractions were bleached with alkaline hydrogen peroxide solutions (4 and 8% v/v) to purify cellulose. After two bleaching cycles, no notable delignification progress was observed, as the bleaching yield or whiteness index did not significantly change in the further cycles. The first bleaching cycle led to a significant reduction in the lignin content at both SWE temperatures. The cellulose purity was higher in the samples obtained at 170 °C and bleached with 4% alkaline hydrogen peroxide. SWE at 180 °C led to greater cellulose oxidation during the bleaching step regardless of the hydrogen peroxide concentration.

Supercritical CO2 and subcritical water extraction of Curcuma longa bioactive compounds

Turmeric, the dry rhizome of the plant Curcuma longa L., is widely valued for its colouring, flavoring, and biological properties that have been mainly attributed to curcuminoids (e.g., curcumin), a group of secondary metabolites. These compounds can be recovered using various extraction techniques, including supercritical CO2 (SC-CO2) extraction and subcritical water extraction (SWE), that are in line with the ‘Green Chemistry’ principles.The purpose of the present study was to evaluate the effect of CO2 flow rate, pressure, and two pre-treatment techniques on curcuminoids extraction from turmeric powder using SC-CO2 extraction. In addition, SWE was employed for the recovery of remained compounds from the turmeric powder left after SC-CO2 extraction. The obtained extracts were analysed with HPLC for the quantitative determination of curcumin. Based on the results, SC-CO2 extraction conditions affected the extraction yield, with the combination of the highest pressure and lowest flow rate resulting in the highest yield. Both pre-treatment methods were also found to increase the extraction yield, whereas Soxhlet extraction was not as efficient as SC-CO2 extraction. In terms of SWE, the highest extraction temperature (210 °C) resulted in the highest extraction yield (61.9 %). However, no curcumin was detected in this sample, indicating the negative effect of temperature on curcumin extraction and the thermal degradation of the latter.

세이지(Salvia officinalis L.) 유래 추출물의 테르펜류 함량 비교

Sage (Salvia officinalis) contains various active compounds, including flavonoids and terpenes. In this study, the terpenes content, including camphor, borneol, and eucalyptol, was analyzed. Both subcritical water and conventional solvent extraction methods were used. Using subcritical water extraction, the optimal extraction conditions were determined based on temperature and time to selectively extract the desired components from the sage. These optimal extraction conditions were as follows: camphor (130°C for 5 min, 2.73±0.39 mg/g), borneol (130°C for 5 min, 0.72±0.07 mg/g), and eucalyptol (150°C for 5 min, 0.51±0.03 mg/g). A comparison of extracts obtained via subcritical water extraction technology and various solvents revealed that the extracts obtained using subcritical water extraction had higher levels of all three components. This indicates that subcritical water extraction is more efficient and faster than traditional solvent extraction methods. Moreover, these results suggest that subcritical water extraction technology has the potential to be applied as an eco-friendly alternative to traditional extraction methods for obtaining active compounds like terpenoids.

Innovative Approach in Sustainable Agriculture: Harnessing Microalgae Potential via Subcritical Water Extraction

Microalgae can contribute to sustainable agriculture and wastewater treatment. This study investigated Tetradesmus obliquus, grown in piggery wastewater (To-PWW), as a biostimulant/biofertilizer compared to biomass grown in synthetic medium (To-B). Subcritical water extraction was tested for disruption/hydrolysis of wet biomass, at three temperatures (120, 170, and 220 ºC) and two biomass loads (1:10 and 1:80 (g dry biomass/mL water)). Extracts were evaluated for germination, and root formation/expansion. Residues were quantified for nutrient composition to assess their biofertilizer potential and tested for their affinity to oil compounds for bioremediation.The best germination was achieved by To-B extracts at 170 ºC (1:10: 148% at 0.2g/L, 1:80: 145% at 0.5g/L). Only To-PWW extracts at 0.2g/L had a significant germination effect (120 ºC: 120-123% for both loads; 170 ºC: 115% for 1:80). To-PWW extract at 120 ºC and 1:10 significantly affected cucumber and mung bean root formation (224 and 268%, respectively). Most extracts significantly enhanced root expansion, with all To-B extracts at 1:10 showing the best results (139-181%). The residues contained essential nutrients (NPK), indicating their biofertilizer potential, helping decrease synthetic fertilizers demands. To-B residues had high affinity to toluene and diesel but lower to used cooking and car oils. To-PWW showed very low affinity to all oil compounds. Finally, all residues were only able to form stable emulsions with the used car oil. This study fully exploits the use of microalgal biomass in sustainable agriculture, producing biostimulant extracts, and residues for biofertilizer and bioremediation, from a low-cost wastewater source.

Subcritical Water Extraction of Allelochemical Compounds from Mucuna Beans

Subcritical Water Extraction of Allelochemical Compounds from Mucuna Beans

Life cycle assessment and cost analysis of innovative agar extraction technologies from red seaweeds

Developing efficient and sustainable extraction technologies for valuable biocompounds from seaweed is crucial to overcome the limitations of conventional technologies. This study aims to compare three innovative technologies for agar extraction from two red seaweed species, G. sesquipedale and G. vermiculophylla: subcritical water extraction (performed at 125 °C, 2.5 atm, 1 min, and at 140 °C, 3.8 atm, 1 s), moderate electric fields (applied at 85 °C for 120 min and 95 °C for 180 min), and a combination of both methods. The comparison used life cycle assessment and life cycle costing methodologies, considering a gate-to-gate approach. The combined technology demonstrated the lowest energy consumption, with 67 MJ/kgagar for G. vermiculophylla and 100 MJ/kgagar for G. sesquipedale. A carbon footprint reduction of up to 94 % was obtained when compared to the control, with 15.9 kgCO2 eq. /kgagar for G. vermiculophylla and 20.4 kgCO2 eq. /kgagar for G. sesquipedale. Using photovoltaic panels as alternative energy further cut carbon emissions by 50 %. The cost analysis showed that the combined technology was the most cost-effective extraction method.

Applying Subcritical Water Extraction to Obtain Bioactive Compounds and Cellulose Fibers from Brewer Spent Grains

Of the three types of waste generated in beer processing, brewer’s spent grain (BSG) is the most abundant and has a high potential for valorization. In this work, defatted BSG (DB) was subjected to an extraction process with subcritical water at different temperatures to obtain extracts rich in phenols and the cellulosic fractions, which were also purified by using hydrogen peroxide (H2O2). The results showed that the dry extracts obtained at 170 °C were richer in phenolics (24 mg Gallic Acid Equivalent (GAE) g−1 DB), but with lower antioxidant capacity (71 mg DB·mg−1 2,2-diphenyl-1-pikryl-hydrazyl). This extract also showed the highest antibacterial potential against L. innocua (80 mg·mL−1) and E. coli (140 mg·mL−1) than those obtained at lower temperatures. The purification of cellulose from the treated residues, using hydrogen peroxide, revealed that DB is a limited source of cellulose material since the bleached fractions showed low yields (20–25%) and low cellulose purity (42–71%), even after four bleaching cycles (1 h) at pH 12 and 8% H2O2. Despite this, the subcritical water extraction method highlights the potential of a simple process as a technological option to convert underutilized side streams like beer bagasse into added-value, potential ingredients for innovative food and pharmaceutical applications.

Green strategies for the valorization of industrial medicinal residues of Serenoa repens small (saw palmetto) as source of bioactive compounds

Serenoa repens is a medicinal plant well-known for its therapeutic potential in treating various urological disorders and prevention of prostatic cancer. However, the extraction process in the pharmaceutical industry leads to the generation of plant residues, typically discarded, wasting valuable resources. In this study, we aimed to explore a series of green extraction strategies to effectively valorize the residues of Serenoa repens fruits. Initially, we employed supercritical CO2 (1.2% yield on dry biomass) on the discarded biomass to identify and quantify residual fatty acids and polyprenols (1.6% of the extract dry weight), a class of unsaturated isoprenoid alcohols with promising biomedical applications. Subsequently, subcritical water extraction was utilized on the exhausted biomass to extract polar compounds. An increase in the extraction yield was observed with the rise in processing temperature up to 180 °C (yields were found higher than 26%). Phenolic compounds and carbohydrate macromolecules profiles were affected by the increased hydrolytic conditions. Polar extracts exhibited robust bioactivities, demonstrating significant antioxidant activity and antimicrobial efficacy against Gram-positive and Gram-negative bacteria strains. Extracts obtained at 180 °C demonstrated the highest efficacy. Furthermore, in vitro assessment of mannans-rich fraction provided a new perspective of potential applications in the cosmeceuticals field. Results underscore the potential of the sustainable extraction biorefinery for the residue of this medicinal plant and demonstrate that, harnessing these bioactive compounds, new sustainable and eco-friendly approaches for its complete utilization can be offered, thereby promoting near-zero waste practices and contributing to a more sustainable future.

The Green Extraction of Blueberry By-Products: An Evaluation of the Bioactive Potential of the Anthocyanin/Polyphenol Fraction.

In the context of a circular economy, this study explores the valorization of blueberry pomace (BP) as a source of bioactive compounds using sustainable extraction methods. Microwave-assisted extraction (MAE) and microwave-assisted subcritical water extraction (MASWE) were employed to obtain two distinct fractions: MAE 1° and MASWE 2°. The first extract, MAE 1°, obtained at 80 °C, had a high total anthocyanin content (21.96 mgCya-3-glu/gextract), making it suitable as a natural pigment. Additionally, MAE 1° exhibited significant enzyme inhibition, particularly against α-amylase and β-glucosidase, suggesting potential anti-diabetic and anti-viral applications. The second extract, MASWE 2°, obtained at 150 °C, contained a higher total phenolic content (211.73 mgGAE/gextract) and demonstrated stronger antioxidant activity. MASWE 2° showed greater inhibition of acetylcholinesterase and tyrosinase, indicating its potential for use in Alzheimer's treatment, skincare, or as a food preservative. MASWE 2° exhibited cytotoxicity against HeLa cells and effectively mitigated H2O2-induced oxidative stress in HaCat cells, with MAE 1° showing similar but less pronounced effects. A tested formulation combining MAE 1° and MASWE 2° extracts in a 3:2 ratio effectively enhanced anthocyanin stability, demonstrating its potential as a heat-stable pigment. The extract characteristics were compared with a conventional method (MeOH-HCl in reflux condition), and the protocol's sustainability was assessed using several green metric tools, which provided insights into its environmental impact and efficiency.

Extraction of fermentable sugars and phenolic compounds from Colombian cashew (Anacardium occidentale) nut shells using subcritical water technology: Response surface methodology and chemical profiling

Subcritical water extraction (SCWE) is a novel technology that uses water at high pressure and temperature to recover bioactive compounds. While promising, further studies are needed to fully understand the potential of SCWE when applied to cashew nut shells (CNS), which are rich in phenolic compounds, carbohydrates, and other natural substances. This study aimed to evaluate SCWE applied to CNS from Vichada, Colombia, using a surface response methodology and to perform a comprehensive chemical profiling of the recovered extracts and the remaining solids. A Box-Behnken experimental design was employed to study the extraction process, focusing on variables such as temperature, pressure, and solid-to-solvent ratio. The liquid extracts were analyzed using ultra-high-performance liquid chromatography and gas chromatography coupled with mass spectrometry, while the extracted solids were characterized using Fourier-transform infrared spectroscopy and scanning electron microscopy. The liquid extracts revealed a variety of compounds, including xylose, glucose, arabinose, long-chain phenols, organic acids, and furans. Extraction conditions significantly influenced the distribution of these compounds, with the optimal conditions for extracting fermentable sugars and organic acids identified as 180 °C, 15 bar, and a 20:1 mL/g solid-to-solvent ratio. The resulting hydrochar comprised lignin (58.82 ± 3.44 %) and structural carbohydrates (approximately 40 %), showing thermal stability up to 200 °C, OH functional groups on its surface, and a textured morphology under microscopy. These by-products have potential applications in various fields. This study demonstrates that SCWE effectively recovers valuable compounds from CNS for use in fermentation processes, suggesting that the resulting hydrochar could be utilized in soil amendment, adsorption, or energy applications. SCWE is highlighted as an innovative and environmentally friendly technology for managing cashew residual biomass, promoting sustainability and circularity in this production chain.

Chemical Profiling and Evaluation of Antioxidant Activity of Artichoke (Cynara cardunculus var. scolymus) Leaf By-Products’ Extracts Obtained with Green Extraction Techniques

This study aimed to determine the effectiveness of different green extraction techniques (GETs) on targeted bioactive compounds from artichoke leaf by-products using deep eutectic solvent extraction (DESE), supercritical CO2 extraction (SCO2E), subcritical water extraction (SWE), and ultrasound-assisted extraction (UAE). Moreover, (HR) LC-ESI-QTOF MS/MS and HPLC-PDA analyses were used to perform qualitative–quantitative analysis on the extracts, enabling the detection of several bioactive compounds, including luteolin, luteolin 7-O-glucoside, luteolin 7-O-rutinoside, apigenin rutinoside, chlorogenic acid, and cynaropicrin as the most representative ones. SWE showed better results than the other GETs (TPC: 23.39 ± 1.87 mg/g of dry plant, dp) and appeared to be the best choice. Regarding UAE, the highest total phenols content (TPC) was obtained with 50:50% v/v ethanol: water (7.22 ± 0.58 mg/g dp). The DES obtained with choline chloride:levulinic acid showed the highest TPC (9.69 ± 0.87 mg/g dp). Meanwhile, SCO2E was a selective technique for the recovery of cynaropicrin (48.33 ± 2.42 mg/g dp). Furthermore, the study examined the antioxidant activity (1.10–8.82 mmol Fe2+/g dp and 3.37–31.12 mmol TEAC/g dp for DPPH• and FRAP, respectively) and total phenols content via Folin–Ciocalteu’s assay (198.32–1433.32 mg GAE/g dp), of which the highest values were detected in the SWE extracts. The relationship among the GETs, antioxidant assays, and compounds detected was evaluated using Principal Component Analysis (PCA). PCA confirmed the strong antioxidant activity of SWE and showed comparable extraction yields for the antioxidant compounds between UAE and DESE. Consequently, GETs selection and extraction parameters optimization can be employed to enrich artichoke leaf by-products’ extracts with targeted bioactive compounds.

Subcritical water extraction on phenolic, flavonoid and antioxidant activity from Orthosiphon Stamineus leaves: Experimental and optimization

Orthosiphon stamineus is rich in phenolic and flavonoid compounds, contributing to its antioxidant properties. This study focuses optimizes the extraction of bioactive compounds from Orthosiphon stamineus leaves using subcritical water (SCW) extraction. Response surface methodology was employed, with temperature (120–180 °C), flow rate (2–8 mL min−1), and extraction time (5–15 min) as independent variables. Dependent variables included extract yield, total phenolic compounds (TPC), total flavonoid compounds (TFC), and antioxidant activity (AA). Optimal conditions were found at 148 °C, 5.1 mL min−1, and 10.5 min, resulting in a maximum yield of 317.6 mg g−1, TPC of 12.71 mg 100 g−1, TFC of 74.09 mg 100 g−1, and AA of 87.48 %. The research highlights the significant influence of temperature as the most crucial parameter, followed by flow rate and extraction time, in achieving the highest yield and bioactive compound content. This investigation holds potential implications for the food processing industry, showcasing the relevance of optimizing extraction conditions to enhance the nutritional and functional properties of natural ingredients like Orthosiphon stamineus in food products.

Valorisation of white wine lees: optimisation of subcritical water extraction of antioxidant compounds

This study explored the extraction of antioxidant compounds from white wine lees using subcritical water extraction (SWE). First, SWE was compared to extraction using conventional solvents mixed with water: 50 % methanol, 50 % ethanol and 50 % acetonitrile. The antiradical activity of the extract increased to 12.8 mg TE/g of extract dry matter (DM) using conventional solvents and to 29.2 mg TE/g DM with SWE, compared to the antiradical activity of dried lees, which was 5.7 mg Trolox Equivalent/g of dry matter (mg TE/g DM). Second, SWE conditions were optimised to obtain lees extracts with a high antioxidant activity by applying a Doehlert design and response surface methodology (RSM). The extraction parameters modulated during RSM optimisation were extraction time (t, 15 – 60 min), temperature (T, 100 – 250 °C) and stirring speed (S, 100 – 1000 RPM). Antioxidant activity was assessed using DPPH and FRAP tests, as well as by measuring the Oxygen Consumption Rate (OCR) of lees extracts. Temperature was found to be the main parameter that had a significant effect on antioxidant activity. The results of the RSM showed the optimal conditions (temperature, duration and speed) for attaining maximum antioxidant activity to be: 240 °C, 15 min and 550 RPM respectively. The best-known antioxidant compounds in white wine lees, Total Polyphenol Content (TPC), Glutathione (GSH) and Total Sulfhydryl groups (TSH) were also quantified. Extracts with the highest antioxidant capacity had the highest TPC and TSH concentrations. In conclusion, this study showed (i) that subcritical water extraction is a green process that has potential as an alternative to using conventional solvents for extracting white wine lees, (ii) the chemical components involved in their antioxidant capacity, and (iii) the potential of the lees for oenological and other industrial applications.

Polysaccharides from Inonotus obliquus employing subcritical water extraction: Extraction optimization, physiochemical properties and bioactivities analysis

As one of the main components in Inonotus obliquus, polysaccharides was potentially to be developed for the special physiochemical properties and bioactivity. However, the low extraction efficiency of Inonotus obliquus polysaccharides (IOP) significantly hindered the in-depth research and development. To achieve a higher extraction yield of IOP, subcritical water was selected and optimized by Box-Behnken Design (BBD) with a more reasonable yield investigation method in the present study. In addition, for the comparative analysis, the physiochemical properties and bioactivity of the subcritical water extracted polysaccharides (IOP-S), purified polysaccharides (IOP-P) and hot water extracted polysaccharides (IOP-W) were all investigated and analyzed. The results showed that the optimal extraction conditions were 200°C, 13.24 min and 30:1 (mL/g), which corresponded to a polysaccharide yield of 14.14±0.17 %. With simple purified process, the IOP-P with high purity (total sugar content of 87.55 %) was suitable for the further study. Compared to IOP-W, a wider molecular weight range (3.4–98 kDa) of polysaccharide was found in IOP-S, as well as higher sugar and polyphenol content, which might be the main reason for the well antioxidant and digestion enzyme inhibition activity. There were also various differences in the monosaccharide composition, micro-morphology and other physiochemical properties, which all suggested that the subcritical water could efficiently extract a special IOP for the fourthly study and development. In summary, the present study proved that subcritical water extraction could significantly improve the extraction efficiency of IOP, and the basic information in physiochemical properties and bioactivities of IOP would promote the development of IOP in the future.