Subcritical Water Research Articles

Network Pharmacology, Molecular Docking, and In Vitro Insights into the Potential of Mitragyna speciosa for Alzheimer’s Disease

Mitragyna speciosa Korth. Havil (MS) has a traditional use in relieving pain, managing hypertension, treating cough, and diarrhea, and as a morphine substitute in addiction recovery. Its potential in addressing Alzheimer’s disease (AD), a neurodegenerative condition with no effective treatments, is under investigation. This study aims to explore MS mechanisms in treating AD through network pharmacology, molecular docking, and in vitro studies. Using network pharmacology, we identified 19 MS components that may affect 60 AD-related targets. The compound–target network highlighted significant interactions among 60 nodes and 470 edges, with an average node degree of 15.7. The KEGG enrichment analysis revealed Alzheimer’s disease (hsa05010) as a relevant pathway. We connected 20 targets to tau and β-amyloid proteins through gene expression data from the AlzData database. Docking studies demonstrated high binding affinities of MS compounds like acetylursolic acid, beta-sitosterol, isomitraphylline, and speciophylline to AD-related proteins, such as AKT1, GSK3B, NFκB1, and BACE1. In vitro studies showed that ethanolic (EE), distilled water (DWE), and pressurized hot water (PHWE) extracts of MS-treated 100 μM H2O2-induced SH-SY5Y cells significantly reduced oxidative damage. This research underscores the multi-component, multi-target, and multi-pathway effects of MS on AD, providing insights for future research and potential clinical applications.

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.

Role of extractive compounds in emulsion stabilisation capacity of wood hemicelluloses

Abstract Hemicellulose-rich extracts obtained by pressurised hot water extraction of wood residues show promise as emulsion stabilisers. However, pressurised hot water extracts (PHWEs) from wood also contain lower molecular weight extractive components that may influence emulsion performance. This study investigated the effect of extractives on emulsion stability using PHWEs obtained from spruce and birch sawdust with or without solvent pre-extraction. The results indicated that extractives negatively affect the physical stability of emulsions in both spruce and birch and influence oxidative stability in spruce after prolonged storage. However, the roles of different extractives in emulsion performance require further investigation.

Conversion of rice husks into antioxidative and prebiotic biomaterials using subcritical water pretreatment and cellulase incubation under high-pressure

Conversion of rice husks into antioxidative and prebiotic biomaterials using subcritical water pretreatment and cellulase incubation under high-pressure

Antioxidant and neuroprotective potential of extracts from Hass avocado peel obtained through a biorefinery process: A sustainable strategy for the valorization of agro-food waste

This study presents a novel three-step biorefinery approach for extracting bioactive compounds from Hass avocado (Persea americana, Mill.) epicarp. By sequentially using supercritical CO2, CO2-expanded ethanol, and subcritical water, we efficiently recovered a diverse range of extracts with distinct phytochemical profiles and potent biological activities. Our innovative extraction strategy outperformed conventional methods, demonstrating the potential of biorefinery for sustainable valorization of agricultural byproducts. Medium and high extracts exhibited strong antioxidant and anticholinesterase activity. For example, the CO2-expanded ethanol extracts demonstrated an ABTS radical cation scavenging capacity of 3.01 ± 0.06 mmol Trolox equivalents/g and an SC50 value of 53.4 ± 1.2 μg/mL for anticholinesterase activity. These findings highlight the feasibility of integrating biorefinery processes into circular economy initiatives to create high-value bioproducts while minimizing waste.

Liquefaction of soybean husk in a semi-continuous mode by subcritical water

Agro-industrial residues, such as soybean husks, are low-cost and can be converted into products. Therefore, the objective of this work was to evaluate the influence of temperature (230, 260, 300, and 340 °C) and the solvent/feed ratio (40 and 80) in the subcritical water process in semi-continuous mode under soybean husks in fermentable sugar, platform chemicals, bio-oil and hydrochar yields. Contextually, fermentable sugar yield of 7.12 ± 0.43 g/ 100 g Soybean husk and bio-oil yield of 30.72 ± g/ 100 g soybean husk were obtained using the condition at 260 °C, solvent/feed ratio 80. Regarding Higher Heating Value, for bio-oil, the values varied between 22.76 ± 0.14 and 24.86 ± 0.09 MJ.kg−1, and for hydrochar samples it varied between 20.14 ± 0.14 and 30.14 ± 0.11 MJ.kg−1.

Experimental solubility of omeprazole in pure and ethanol-modified subcritical water

The current research aimed to study and measure the solubility of omeprazole (used to treat and reduce stomach acid) for the first time in pure subcritical and ethanol-modified water. These tests have been performed in the 25–130 °C temperature range and constant pressure of 20 bar with the use of 0–10% ethanol weight as the cosolvent. The solubility of omeprazole in subcritical water ranged from 0.0697 × 10–4 to 5.843 × 10–4 mol fraction at temperatures from 25 to 130 °C, respectively. The highest solubility was obtained at 130 °C with a 10% ethanol weight as the cosolvent, which is indicative of a significant trend of improvement in omeprazole solubility with the increase in temperature and the use of ethanol cosolvent in various weight percentages. The solubility experimental data obtained were fitted using the semi-experimental and modified Apelblat linear model, and the findings revealed an excellent correlation between the experimental data and the data received from the linear and modified Apelblat model. Also, at the 25–130 °C temperature range, no degradation, phase transition, or other changes in the structure and physical state of the drug were observed.

Characterization and Modeling of Gravity-Driven Flashing of Superheated Water in a Pool Heated from Below

Gravity-driven flashing of superheated water, the topic of this paper, is a phase change phenomenon that is tightly linked with some of the safety issues of a spent-fuel-pool loss-of-cooling accident. As detailed in this article, the phenomenon has been empirically studied and characterized within the Aquarius laboratory-scale experimental device. Primarily, the performed tests unveil the occurrence conditions of the gravity-driven flashing phenomenon in a pool heated from below and its coupling with the degassing of dissolved gases that may take place within the liquid. Next, a set of dimensionless correlations describing the studied heat and mass transfers is derived from the data and presented for both the single-phase and the two-phase regimes of any conducted test. Then, a lumped-parameter model, relying on those correlations and describing the studied physics, is introduced. The model resolves the coupled mass and energy balance equations of the heated liquid pool. Last, this model is used to simulate a selected reference test. The performed simulations are successfully compared with the available empirical data, with moderate discrepancies, thereby verifying the adequateness of the proposed model.

Effects of Sea Lettuce (Ulva Prolifera) Extracted via Subcritical Water on the Physicochemical Properties of Pork Patties

Effects of Sea Lettuce (Ulva Prolifera) Extracted via Subcritical Water on the Physicochemical Properties of Pork Patties

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.

Molecular dynamics simulation of extraction of Curcuma longa L. extract using subcritical water

Humans have utilized plants for various purposes, including sustenance and medical treatment for millennia. Researchers have extensively investigated medicinal plants’ potential in drug development, spurred by their rich array of chemical compounds. Curcumin, a valuable bioactive compound, is extracted from Turmeric, known by the scientific name Curcuma Longa L. Notably, curcumin boasts potent antioxidant and anti-inflammatory properties, making it a promising candidate for treating cancer and other microbial diseases. Therefore, the simulation study of the extraction of this important medicinal compound by water, which is a green solvent, was carried out. This study employed molecular dynamics simulation for the first time to explore the extraction of Curcuma Longa L. extract using subcritical water. The simulations were carried out at constant pressure and different temperatures, using the Compass force field in the Lammps simulation package. The findings revealed an increase in the amount of Curcuma longa extract with rising temperature, indicating a weakening of hydrogen bonds in water molecules. Water lost its polar state with increasing temperature and became a suitable non-polar solvent for extracting non-polar compounds. The average absolute relative deviation (AARD) for calculated and simulated density data was 6.45%.

Valorization of White Lupin Straw Through Mild Dilute Acid Hydrothermal Treatment: A Sustainable Route for Monosaccharide and 5-Hydroxymethylfurfural Production

This study investigates the potential use of white lupine straw (WLS), an underutilized agricultural by-product, as a raw material to produce valuable biochemicals such as monosaccharides and 5-hydroxymethylfurfural (5-HMF) through hydrothermal pretreatment. The aim was to optimize mild reaction conditions to maximize the recovery of these products while minimizing degradation. The hydrothermal treatment of WLS in subcritical water with trace amounts of sulfuric acid was performed, followed by a two-step approach to evaluate the yields of hemicellulose and 5-HMF. The highest monosaccharide yield (163 g/kg) was achieved at temperatures between 174 and 181 °C and a holding time of 7–14 min, while the 5-HMF production was 139.9 g/kg at 199–203 °C and after 0.5–4.5 min. These results suggest that optimal 5-HMF production also increases the remaining solid residue. This study highlights the feasibility of WLS as a sustainable, low-cost biomass resource. It highlights the balance between temperature and time to maximize valuable product yields. The results contribute to advancing biorefinery processes by demonstrating that WLS can be effectively converted into bioethanol precursors and industrial chemicals, supporting circular bioeconomy principles and providing an environmentally friendly alternative to burning crop residues.

Corrosion Ferritic Stainless Steel in a Simulated Hydrothermal Liquefaction Bioconversion Aqueous Solution: Effect of Surface Cr Content

Abstract The objective of this study was to determine the effect of surface Cr content on the corrosion of ferritic stainless steels in hot pressurized alkaline water (310 °C at 10 MPa) simulating a hydrothermal liquefaction bioconversion medium. Two methods to increase the Cr surface content were investigated: (i) selecting commercial grades of ferritic stainless steel with an increasing Cr content and (ii) applying a Cr coating (chromizing) to a low-Cr (Type 409) ferritic stainless steel. The observed parabolic-like corrosion kinetics were analyzed and discussed in terms of the structure and composition of the double layered oxide films that formed. The (surface) Cr content is a critical factor affecting corrosion. Corrosion was reduced by 66% (after 20 days exposure) when increasing the Cr content from 9 wt.% (P91) to 21 wt.% (SS443) in the commercial grades of ferritic stainless steel. Moreover, corrosion was reduced by 84% (after 20 days exposure) by chromizing the surface of a low-Cr (Type 409) ferritic stainless steel. Improved corrosion protection was attributed to increased Cr incorporation into the inner (barrier) Fe(Fe1-nCrn)2O4 layer, with the formation of a Cr2O3 layer (resulting from chromizing) being most beneficial.

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.

Hydroxide-ion induced complete mineralization of poly(tetrafluoroethylene-co-hexafluoropropylene) copolymer (FEP) in subcritical water

Decomposition of poly(tetrafluoroethylene-co-hexafluoropropylene) copolymer (FEP) in supercritical and subcritical water was investigated with the aim of waste treatment. The efficiency of such decomposition was examined by using either oxidizing agents (O2, H2O2) or an alkaline reagent (KOH). When O2 was chosen, the highest F– and CO2 yields, 75 % and 64 %, respectively, were obtained from a reaction of FEP in supercritical water at 384 °C for 24 h. Under these conditions, traces of CHF3 were detected in the gas phase, the amount of which decreased with increasing the reaction time·H2O2 gave slightly higher reactivity than O2. In contrast, reactions with KOH induced efficient fluorine mineralization. When FEP reacted in 3.0 M KOH solution at 360 °C for 18 h, the F– yield reached 98 %. Hence, complete fluorine mineralization was achieved, where very little CO2 (∼0% yield) and no CHF3 were generated in the gas phase. Furthermore,19F NMR spectroscopy and combustion-ion chromatography revealed that the reaction solutions did not contain any organofluorine compounds during the reactions. FEP decomposed, releasing F– into the reaction solution, resulting in the formation of amorphous carbon in the residue.

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

Subcritical water hydrolysis of soybean hulls pretreated by steam explosion: High pressure integrated process strategy

Steam explosion (SE) pretreatment and sequentially subcritical water hydrolysis (SWH) was studied. Industrially, there is an advantage in using this process strategy, since it uses the same equipment and instrumentation, without the need to transport the raw material in separate stages. The influence of severity factors (SF) (2.75, 3.05, and 3.35) and solvent used (distilled water and 0.5 % w/w of H2SO4) were evaluated in the SE efficiency. SWH was perform in integrated processing using the best pre-treatment conditions. The influence of temperature (230 and 260 °C) and the solvent/feed ratio (40 and 80) were considered. The integrated system resulted in a FS yield of 19.19 ± 0.49 g/ 100 g SH, for a condition Integrated 230 °C, S/F-40, a FS yield 3.3 times greater than that obtained in the same condition with untreated soybean hulls, demonstrating the advantage of perform the process under this operating strategy (SE + SWH)