Subcritical Water Extraction Research Articles

Extraction characteristics and hydrolysis of flavoring compounds of cinnamon (Cinnamomum zeylanicum) under subcritical-water conditions

Subcritical water extraction (SWE) of four flavoring compounds from cinnamon was performed at various temperatures and for various extraction times. The extraction temperature (°C) and time (min) corresponding to the maximum content of flavoring compounds were 190 °C and 5 min for cinnamyl alcohol, 200 °C and 20 min for cinnamic acid, 130 °C and 10 min for cinnamaldehyde, and 170 °C and 20 min for coumarin, respectively. Cinnamaldehyde underwent structural conversion to benzaldehyde via hydrolysis at high temperatures, and the rate of conversion rapidly increased above 150 °C. The extraction efficiency using subcritical water was slightly higher or comparable to that using conventional extractants. SWE is a potential and highly selectivity technology for extracting flavoring compounds from cinnamon.

Green-based processes applied for valorization of peanut by-product: In vitro evaluation of antioxidant and enzymatic inhibition capacities

Peanut (Arachis hypogea L.) industrial processing generates underused by-products, which are mostly discharged. In this work, extracts from peanut by-product were obtained by Supercritical Fluid Extraction (SFE), Pressurized Liquid Extraction (PLE) and Subcritical Water Extraction (SWE), and compared to Soxhlet (SOX). Yield values varied from 12.94% to 37.65% for SOX-water and SWE, respectively. The quality of the extracts was evaluated by total phenolic content (TPC), antioxidant and enzymatic inhibition potentials, and fatty acids profile. Best TPC performance and high antioxidant capacity were obtained from samples using ethanol/water by PLE and Soxhlet. High inhibition of human salivary α-amylase was achieved by PLE and Soxhlet samples recovered with ethanol/water mixture. The inhibition of porcine pancreatic α-amylase was higher from samples by SFE and Soxhlet with ethanol. High-pressure methods are appealing alternatives for the recovery of bioactive extracts from peanut by-products, with functional properties and potential inhibitor of digestive enzymes.

Comparative Chemical Profiling of Underexploited Arctostaphylos uva-ursi L. Herbal Dust Extracts Obtained by Conventional, Ultrasound-Assisted and Subcritical Water Extractions

Comparative Chemical Profiling of Underexploited Arctostaphylos uva-ursi L. Herbal Dust Extracts Obtained by Conventional, Ultrasound-Assisted and Subcritical Water Extractions

Extraction of chlorogenic acids from hibiscus (Hibiscus syriacus L.) by subcritical-water

Chlorogenic acids are formed from hibiscus (Hibiscus syriacus L.) by ester bonding of caffeic acid and quinic acid, and they have isomers named neochlorogenic acid (NCGA) and cryptochlorogenic acid (CrCGA) that are esterified on different sites of caffeic acid. Subcritical-water extraction (SWE) is an ecofriendly and highly efficient technique because it utilizes a nontoxic solvent and has a very short extraction time. Twenty different SWE conditions were applied to hibiscus, with extraction times of 10–40 min, and extraction temperatures of 110–190 °C. The concentrations of chlorogenic acid, NCGA, and CrCGA were maximal for extraction conditions of 190 °C/10 min, 110 °C/10 min, and 130 °C/40 min, respectively. The extraction efficiency varied with the extraction conditions among the three isomers due to the hydrophilicity of the hydroxyl residue depending on the steric structure, the stability of the steric structure varying with the position of the acyl group, and the isomerization caused by the reversible movement of the acyl group.

Application of Pulsed Electric Field as a Pre-Treatment for Subcritical Water Extraction of Quercetin from Onion Skin.

Pulsed electric field (PEF) treatment promotes the electroporation of biological membranes, and if included as a pre-treatment, could improve the extraction of certain constituents therefrom. The aim of this study was to determine the optimal extraction conditions for extracting the flavonoid quercetin from dried onion skin and to establish whether the yield could be enhanced by combining PEF pre-treatment with an eco-friendly extraction method that uses subcritical water extraction (SWE). Samples of onion skin were treated with PEF under conditions of varying electric field strength (0.5–2.5 kV/cm) and duration (5–120 s). SWE was then performed with an extraction time of 15 min and at temperatures ranging from 105 °C to 185 °C. Among the conditions tested, the yield of total quercetin was the highest after pretreatment with PEF at 2.5 kV/cm for 15 s, followed by SWE at 145 °C for 15 min (yield 19.25 ± 0.77 mg/g dried onion skin, mean ± standard deviation). Pretreatment with PEF improved the yield of total quercetin extracted by 33.22% compared with the PEF-untreated samples. These findings demonstrate that pretreatment of onion skin with PEF has the potential to improve flavonoid extraction.

Structure Identification of Two Polysaccharides from Morchella sextelata with Antioxidant Activity.

Mushrooms of the Morchella genus exhibit a variety of biological activities. Two polysaccharides (MSP1-1, 389.0 kDa; MSP1-2, 23.4 kDa) were isolated from Morchella sextelata by subcritical water extraction and column chromatography fractionation. Methylation and nuclear magnetic resonance analysis determined MSP1-1 as a glucan with a backbone of (1→4)-α-D-glucan branched at O-6, and MSP1-2 as a galactomannan with coextracted α-glucan. Light scattering analysis and transmission electron microscopy revealed that MSP1-1 possessed a random coil chain and that MSP1-2 had a network chain. This is the first time that a network structure has been observed in a polysaccharide from M. sextelata. Despite the differences in their chemical structures and conformations, both MSP1-1 and MSP1-2 possessed good thermal stability and showed antioxidant activity. This study provides fundamental data on the structure–activity relationships of M. sextelata polysaccharides.

Bioactive Compounds from Cocoa Husk: Extraction, Analysis and Applications in Food Production Chain.

Cocoa husk is considered a waste product after cocoa processing and creates environmental issues. These waste products are rich in polyphenols, methylxanthine, dietary fibers, and phytosterols, which can be extracted and utilized in various food and health products. Cocoa beans represent only 32–34% of fruit weight. Various extraction methods were implemented for the preparation of extracts and/or the recovery of bioactive compounds. Besides conventional extraction methods, various studies have been conducted using advanced extraction methods, including microwave-assisted extraction (MAE), ultrasonic-assisted extraction (UAE), subcritical water extraction (SWE), supercritical fluid extraction (SFE), and pressurized liquid extraction (PLE). To include cocoa husk waste products or extracts in different food products, various functional foods such as bakery products, jam, chocolate, beverage, and sausage were prepared. This review mainly focused on the composition and functional characteristics of cocoa husk waste products and their utilization in different food products. Moreover, recommendations were made for the complete utilization of these waste products and their involvement in the circular economy.

Evaluation of the Biological Potential of Himanthalia elongata (L.) S.F.Gray and Eisenia bicyclis (Kjellman) Setchell Subcritical Water Extracts.

Neuroprotection is a need that remains unmet in treating chronic neurodegenerative disorders, despite decades of extensive research. To find new neuroprotective compounds, extracts of Himanthalia elongata (L.) S.F.Gray and of Eisenia bicyclis (Kjellman) Setchell were obtained through subcritical water extraction applying a four-step temperature gradient. The fractions obtained were screened against brain enzymes involved in neurodegenerative etiology, namely in Alzheimer’s and Parkinson’s diseases, and against reactive oxygen and nitrogen species, all contributing factors to the progression of neurodegeneration. Results showed no significant enzyme inhibition but strong radical scavenging activities, particularly in the fourth fraction, extracted at the highest temperature (250 °C), highlighting their ability to retard oxidative and nitrosative stresses. At higher temperatures, fractions were composed of phenolic compounds and Maillard reaction products, a combination that contributed to their antioxidant activity and, consequently, their neuroprotective properties. All fractions were evaluated for the presence of iodine, 14 organochlorine and 7 organophosphorus pesticides, and pharmaceuticals used in Alzheimer’s and Parkinson’s diseases (14), psychiatric drugs (8), and metabolites (8). The fractions studied did not present any of the screened contaminants, and only fraction 1 of E. bicyclis should be used with caution due to iodine content.

High-yield recovery of highly bioactive compounds from red ginseng marc using subcritical water extraction

Red ginseng marc (RGM), a byproduct obtained during manufacturing various ginseng products, which is typically discarded as waste, contains numerous residual bioactive compounds. However, the recovery of bioactive compounds, including transformed ginsenosides, from RGM using conventional extraction techniques is difficult. In this study, subcritical water was used for a quick and high-yield extraction of the bioactive compounds in RGM. Furthermore, the chemical species and antioxidant activities of the extracts were analyzed. Extraction was performed in the temperature range and duration of 140–200 °C and 15–90 min, respectively, to determine the optimal conditions for achieving the highest extraction yield and bioactivity. Under the optimized conditions (200 °C and 15 min), an extraction yield of 48 wt% was achieved, which was 1.8 and 4.1 times higher than those achieved via Soxhlet extraction with water and 80% ethanol, respectively (8 h). In addition, the antioxidant activity of the subcritical water extract was 2.7–78.7 times and 2.8–9.8 times higher than those of the extracts obtained using the Soxhlet method with water and 80% ethanol, respectively. The total ginsenoside content of the extract was 30 mg/g, and G-Rf, a transformed ginsenoside, was the primary component of the extract.

Comprehensive Study of Traditional Plant Ground Ivy (Glechoma hederacea L.) Grown in Croatia in Terms of Nutritional and Bioactive Composition.

In the present study, ground ivy was harvested from different natural habitats in Croatia and subjected to screening analysis for nutritional and bioactive composition. To achieve maximum recovery of phenolic compounds, different extraction techniques were investigated—heat-assisted (HAE), microwave-assisted (MAE) and subcritical water (SWE) extraction. Prepared extracts were analysed by spectrophotometric methods, LC-MS/MS and HPLC-PAD methodologies. Results regarding nutritive analyses, conducted using standard AOAC methods, showed the abundance of samples in terms of insoluble dietary fibre, protein, calcium and potassium, while rutin, chlorogenic, cryptochlorogenic, caffeic and rosmarinic acid were the most dominant phenolic compounds. In addition, LC-MS/MS analysis revealed the presence of apigenin and luteolin in glycosylated form. Maximum recovery of target phenolic compounds was achieved with MAE, while SWE led to the formation of new antioxidants, which is commonly known as neoformation. Moreover, efficient prediction of phenolic composition of prepared extracts was achieved using NIR spectroscopy combined with ANN modelling.

Optimized extraction of phenolic antioxidants from red pitaya (Hylocereus polyrhizus) seeds by subcritical water extraction using response surface methodology

Optimized extraction of phenolic antioxidants from red pitaya (Hylocereus polyrhizus) seeds by subcritical water extraction using response surface methodology

Anticancer and Apoptotic Activity in Cervical Adenocarcinoma HeLa Using Crude Extract of Ganoderma applanatum.

Cancer is currently one of the foremost health challenges and a leading cause of death worldwide. Cervical cancer is caused by cofactors, including oral contraceptive use, smoking, multiparity, and HIV infection. One of the major and considerable etiologies is the persistent infection of the oncogenic human papilloma virus. G. applanatum is a valuable medicinal mushroom that has been widely used as a folk medicine for the treatment and prevention of various diseases. In this study, we obtained crude extract from G. applanatum mushroom with a subcritical water extraction method; cell viability assay was carried out and the crude extract showed an antiproliferative effect in HeLa cells with IC50 of 1.55 ± 0.01 mg/mL; however, it did not show any sign of toxicity in HaCaT. Protein expression was detected by Western blot, stability of IκBα and downregulation of NFκB, IKKα, IKKβ, p-NFκB-65(Ser 536) and p-IKKα/β(Ser 176/180), suggesting loss of survival in a dose-dependent manner. RT-qPCR revealed RNA/mRNA expression; fold changes of gene expression in Apaf-1, caspase-3, cytochrome-c, caspase-9, Bax and Bak were increased, which implies apoptosis, and NFκB was decreased in a dose-dependent manner. DNA fragmentation was seen in the treatment groups as compared to the control group using gel electrophoresis. Identification and quantification of compounds were carried out by GC–MS and HPLC, respectively; 2(5H)furanone with IC50 of 1.99 ± 0.01 μg/mL could be the responsible anticancer compound. In conclusion, these findings suggest the potential use of the crude extract of G. applanatum as a natural source with anticancer activity against cervical cancer.

Effect of Temperatures on Polyphenols during Extraction

Background: Polyphenols are a set of bioactive compounds commonly found in plants. These compounds are of great interest, as they have shown high antioxidant power and are correlated to many health benefits. Hence, traditional methods of extraction such as solvent extraction, Soxhlet extraction and novel extraction technologies such as ultrasound-assisted extraction and subcritical water extraction (SWE) have been investigated for the extraction of polyphenols. Scope and Approach: Generally, for traditional extractions, the total phenolic content (TPC) is highest at an extraction temperature of 60–80 °C. For this reason, polyphenols are regularly regarded as heat-labile compounds. However, in many studies that investigated the optimal temperature for subcritical water extraction (SWE), temperatures as high as 100–200 °C have been reported. These SWE extractions showed extremely high yields and antioxidant capacities at these temperatures. This paper aimed to examine the relevant literature to identify and understand the mechanisms behind this discrepancy. Results: Thermal degradation is the most common explanation for the degradation of polyphenols. This may be the case for specific or sub-groups of phenolic acids. The different extraction temperatures may have also impacted the types of polyphenols extracted. At high extraction temperatures, the formation of new compounds known as Maillard reaction products may also influence the extracted polyphenols. The selection of source material for extraction, i.e., the plant matrix, and the effect of extraction conditions, i.e., oxidation and light exposure, are also discussed. The overestimation of total phenolic content by the Folin–Ciocâlteu assay is also discussed. There is also a lack of consensus in TPC’s correlation to antioxidant activity.

Valorisation of microalga Tetradesmus obliquus grown in brewery wastewater using subcritical water extraction towards zero waste

In this study, green technology was applied for extraction of compounds from wastewater-grown microalga biomass with the final goal of obtaining microbiologically safe products within a sustainable biorefinery process with zero waste. Tetradesmus obliquus biomass resulting from brewery wastewater treatment, with (To-CO2) and without CO2 supplementation (To), was submitted to subcritical water extraction (SWE) at temperatures 120–220 °C for 10 min. The impact of the different SWE conditions in the obtained liquid extracts and solid residues were investigated for metal content and chemical and microbiological profiles. Gas chromatography–mass spectrometry analysis indicated that of T. obliquus extracts and residues are valuable sources of aliphatic saturated, unsaturated, and alkylated (mostly methylated) hydrocarbons, phenols, esters, and ketones. Polyphenolic content and antioxidant activity were enhanced approximately 4 times by increasing the temperature from 120 to 220 °C. Also, the content of polyphenols doubled when T. obliquus was supplemented with CO2 for all the tested temperatures (To: 0.249–1.016 mg GAE mL−1; To-CO2: 0.437 – 1.767 mg GAE mL−1). The microbiological analysis determined that liquid extracts and residues represent safe sources of bioactive components that can be used in different industries. In addition, the lower content of heavy metals in residues suggests the possibility of using the solid waste as animal feed or soil conditioner in agricultural applications.

Neuroprotective Effect of Eco-Sustainably Extracted Grape Polyphenols in Neonatal Hypoxia-Ischemia.

Polyphenols are natural compounds with promising prophylactic and therapeutic applications. However, their methods of extraction, using organic solvents, may prove to be unsuitable for daily consumption or for certain medical indications. Here, we describe the neuroprotective effects of grape polyphenols extracted in an eco-sustainable manner in a rat model of neonatal hypoxia-ischemia (NHI). Polyphenols (resveratrol, pterostilben and viniferin) were obtained using a subcritical water extraction technology to avoid organic solvents and heavy metals associated with chemical synthesis processes. A resveratrol or a polyphenol cocktail were administered to pregnant females at a nutritional dose and different time windows, prior to induction of NHI in pups. Reduced brain edema and lesion volumes were observed in rat pups whose mothers were supplemented with polyphenols. Moreover, the preservation of motor and cognitive functions (including learning and memory) was evidenced in the same animals. Our results pave the way to the use of polyphenols to prevent brain lesions and their associated deficits that follow NHI, which is a major cause of neonatal death and disabilities.

Sub-critical water extraction of reducing sugars and phenolic compounds from date palm fruit

Sub-critical water extraction of reducing sugars and phenolic compounds from date palm fruit

Research Progress in Subcritical Water Extraction of Bioactive Substances from Plants

Research Progress in Subcritical Water Extraction of Bioactive Substances from Plants

Green Extraction of Carrageenans from Mastocarpus stellatus.

The recovery of biopolymers from natural resources using eco-friendly extraction technologies that enhance their mechanical properties has gained attention in recent years. In this context, this work deals with the isolation of hybrid carrageenans from Mastocarpus stellatus red seaweed using subcritical water extraction operating in a wide range of thermal conditions (70–190 °C). The extracted biopolymers were analyzed by means of either Fourier-Transform infrared, nuclear magnetic resonance, rheological or cell viability assays. In parallel, the fundamental chemical composition of the seaweed used as raw material, as well as the main phytochemical properties of the soluble liquid extracts, were also studied. Results indicated that thermal extraction conditions significantly affected the rheological behavior of the recovered hybrid carrageenans. The hybrid carrageenan extraction yields varied, with results between 10.2 and 30.2% being the highest values obtained at hydrothermal treatment of 130 °C. A wide palette of viscous features was identified for recovered hybrid carrageenans, with the strongest rheology properties observed at the same temperature. It should be remarked that the maximum inhibitory effect was also obtained at 130 °C for both the ovarian carcinoma cell line (A2780) (65%, IC50: 0.31 mg/mL) and lung carcinoma cell line (A549) (59%, IC50: 0.41 mg/mL).

Selective extraction of oxygenated terpene in caraway (Carum carvi L.) using subcritical water extraction (SWE) technique

Caraway contains terpenes such as carvone, limonene and carveol, that have antibacterial and antifungal properties. Subcritical-water extraction (SWE) can be used to extract terpenes by changing temperature under high pressure. This study evaluated the SWE of terpenes from caraway when varying the extraction conditions of temperature (110 °C–190 °C), time (5–15 min), and particle size (>1000, 850–1000, 425–850, and < 425 μm). The optimal conditions for the extraction of carvone, which determines the quality of caraway, were found to be 170 °C, 15 min, and a particle size of < 425 μm. Also, the carvone yield was much higher when using SWE (28.5 mg/g caraway) than for solvent extraction (20.2 mg/g caraway) and hydrodistillation (19.8 mg/g caraway). The overall results showed that oxygenated terpene like carvone has a high solubility in subcritical water, and nonoxygenated terpene like limonene can partially be converted to carvone via a process of SWE.

Physicochemical and biofunctional properties of Sargassum thunbergii extracts obtained from subcritical water extraction and conventional solvent extraction

The aim of this study was to analyze Sargassum thunbergii extracts prepared via subcritical water extraction (SWE). The total maximum contents of phlorotannin, total sugars, and reducing sugars of the S. thunbergii extracts were (13.57 ± 0.19) mg phloroglucinol equivalent (PGE)/g of dry sample, (61.95 ± 0.75) mg glucose/g of dry sample, and (48.51 ± 1.40) mg glucose/g of dry sample in extracts prepared at 180 °C, 150 °C, and 180 °C, respectively. The antioxidant activity of S. thunbergii extracts in the ABTS, DPPH, and FRAP assays was the highest at extraction temperature of 180 °C, with values of (17.99 ± 0.02, 56.72 ± 0.09, and 29.79 ± 0.11) mg Trolox equivalent (TE)/g of dry sample, respectively. In the extract prepared at 180 °C, the largest range of phenolic compounds was identified, and the antibacterial activity was strongest. In the agar well diffusion assay, 50 mg/mL S. thunbergii extract obtained at 180 °C resulted in the largest zones of clearance for Escherichia coli and Bacillus cereus and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were higher for E. coli than for B. cereus.