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Hesperidin is a phenolic compound usually found in citrus fruits, which is known for its anti-inflammatory and antioxidant properties. This bioactive compound has already been used to formulate medications to treat chronic venous insufficiency. In this work, through a system which allows the in-line coupling of the pressurized liquid extraction (PLE) and high-intensity ultrasound (HIUS) with solid phase extraction (SPE), and analysis by high-performance liquid chromatography with UV-Vis detector (HPLC-UV) in on-line mode, a method was developed to obtain, separate, and quantify hesperidin from the industrial waste of lime. An eco-friendly approach with water and ethanol as extraction solvents was used. Parameters such as temperature (80, 100, and 120 °C) and HIUS power (0, 200, and 400 W) were evaluated regarding hesperidin yield. In this context, the higher hesperidin yield (18.25 ± 1.52 mg/g) was achieved using water at a subcritical state (120 °C and 15 MPa). The adsorbent SepraTM C-18-E isolated hesperidin from the other extracted compounds employing 50% ethanol in the SPE elution. The possibility ofon-lineanalysis coupling a high-performance liquid chromatograph to an ultraviolet detector (HPLC-UV) system was studied and shown to be a feasible approach for developing integrated technologies. Conventional extractions and their antioxidant capacities were evaluated, highlighting the advantages of the HIUS-PLE-SPE extractive method. Furthermore, the on-linechromatographic analysis showed the potential of the HIUS-PLE-SPE- HPLC-UV system to quantify the extracted compounds in real time.

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ABSTRACTThis study evaluated the effectiveness of a semi-continuous flow-through subcritical water hydrolysis (SWH) pretreatment of brewer's spent grains (BSG) for subsequent application in the anaerobic digestion (AD) process. BSG pretreatment was conducted at 160 °C and 15 MPa with a flow rate of 10 mL water min-1 and 15 g water g-1 BSG. The results revealed that SWH attacked the hemicellulose structure, releasing arabinose (46.54 mg g-1) and xylose (39.90 mg g-1) sugars, and proteins (34.89 mg g-1). The start-up of anaerobic reactors using pretreated BSG (747.71 L CH4 kg-1 TVS) increased the methane yield compared with the reactor without pretreatment (53.21 L CH4 kg-1 TVS). For the process with pretreatment, the generation of electricity (134 kWh t-1 BSG) and heat (604 MJ t-1) are responsible for the mitigation of 43.90 kg CO2 eq t-1 BSG. The adoption of SWH as an eco-friendly pretreatment of biomass for AD could be a technological route to increase methane-rich biogas and bioenergy production, supporting the circular economy transition by reducing the carbon footprint of the beer industry.

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The untargeted metabolomics approach was used to compare the chemical profiles of acerola (Malpighia emarginata DC.) pomace extracts. The effect of drying the raw material before subcritical water extraction (SWE) at different temperatures on the yield, phenolic content, and in vitro antioxidant activity was evaluated. The results were compared with those obtained via Soxhlet and the findings suggest that SWE saves time (15 min) and solvent for extracting valuable components as compared to Soxhlet (6 h). An increase in temperature significantly improved the extraction yield (23.9 to 33.4 %), phenolic content (119.1 to 362 mgGAEg-1), and antioxidant activity, and higher values were obtained with SWE as compared to Soxhlet. The most abundant compounds detected by UPLC-ESI-QTOF-MS were ascorbic acid, kaempferol, quercetin, and isorhamnetin. The investigation of different moisture contents in the SWE showed promising results for eliminating the drying operation, saving time and energy, and obtaining highly concentrated phenolic-rich by-products.

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The importance of bioactive peptides lies in their diverse applications in the pharmaceutical and food industries. In addition, they have been projected as allies in the control and prevention of certain diseases due to their associated antioxidant, antihypertensive, or hypoglycemic activities, just to mention a few. Obtaining these peptides has been performed traditionally by fermentation processes or enzymatic hydrolysis. In recent years, the use of supercritical fluid technology, specifically subcritical water (SW), has been positioned as an efficient and sustainable alternative to obtain peptides from various protein sources. This review presents and discusses updated research reports on the use of subcritical water to obtain bioactive peptides, its hydrolysis mechanism, and the experimental designs used for the study of effects from factors involved in the hydrolysis process. The aim was to promote obtaining peptides by green technology and to clarify perspectives that still need to be explored in the use of subcritical water in protein hydrolysis.

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Soursop (Annona muricata L.) seeds, which is a residue obtained from juice agro-industries, were subjected to supercritical fluid extraction (SFE) and subcritical water extraction (SWE) in single or combined mode to extract the potential value-added compounds. Different extraction methods were evaluated in terms of the extraction yield, phenolics content, antioxidant activity (DPPH, ABTS, and FRAP), and Maillard reaction products. The extracts were analyzed using SEM, GC-MS, and LC-MS/MS techniques. The temperature and a combination of high-pressure techniques positively affected the overall results (SFE + SWE), affording nonpolar and polar extracts rich in phenolics and antioxidant compounds. SEM analysis showed that the use of SFE caused modifications in the cell wall, and the oil fraction was rich in fatty acids. Twenty-nine compounds associated with soursop seed extracts were detected for the first time using LC-MS/MS, showing the potential of the raw material as well as promoting resource re-utilization in circular economy.

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Many natural compounds, found mainly in plants, are associated with the treatment of various diseases. The search for natural therapeutic agents includes compounds with antiviral and anti-inflammatory activities. Among the many steps involved in bioprospection, extraction is the first and most critical step for obtaining bioactive compounds. One of the main advantages of using compressed fluids extraction is the high quality of the final product obtained due to the use of green solvents, while the selectivity towards target compounds can be tuned by adjusting the process parameters, especially pressure, temperature and solvent characteristics. In this review, a discussion is provided on the power of compressed fluids, such as supercritical fluid extraction (SFE), pressurized liquid extraction (PLE) and subcritical water extraction (SWE) to obtain antiviral and anti-inflammatory compounds from natural sources. In addition, an adequate knowledge about the identity and quantity of the compounds present in the extract is essential to correlate biological activity with chemical composition. Phytochemical profiling tools used for identification and quantification of these bioactive natural compound are also discussed. It can be anticipated that after the current SARS-COV-2 pandemic, the search of new natural compounds with antiviral and anti-inflammatory activity will be a hot research topic, so, this review provides an overview on the technologies currently used that could help this research.

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Subcritical water has potential as an environmentally friendly solvent for applications including hydrolysis, liquefaction, extraction, and carbonization. Here, we report hydrolysis of sugarcane straw, an abundant byproduct of sugar production, in a semi-continuous reactor at reaction temperatures ranging from 190 to 260°C and at operating pressures of 9 and 16MPa. The target hydrolysis products were total reducing sugars. The main products of sugarcane straw hydrolysis were glucose, xylose, arabinose, and galactose in addition to 5- hydroxymethylfurfural and furfural as minor byproducts. Fourier transform infrared spectroscopy and thermogravimetric analysis provided additional information on the surface and bulk composition of the residual biomass. Char was present on samples treated at temperatures equal to and greater than 190°C. Samples treated at 260°C contained approximately 20wt% char, yet retained substantial hemicellulose and cellulose content. Hydrolysis temperature of 200°C provided the greatest TRS yield while minimizing char formation.

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The extraction of calcareous chitin from shrimp cephalothorax was successfully achieved using a subcritical water treatment to attain a deproteinization up to 96%. The treatments also increased the crystalline domain size in the α-chitin fibers. An experimental design of Taguchi allowed the optimization of experiments. The macroelements identified in all samples were Ca, P, S, K, Cl and Al, whereas Cr, Mn, Fe, Ni, Cu, Zn, Br and Sr were also detected as microelements. The assigned crystalline phases by XRD were α-chitin, calcite, HAP and traces of quartz. The presence of these phases was corroborated by ATR-FTIR and SEM-EDS analyses. The highest content of α-chitin (82.2wt%) was obtained for the 0.17 chitin:dH2O (wt/wt) ratio for 30min treatment at 260°C. Noteworthy, this treatment promotes the crystallization of both minerals as microcrystals of calcite and nanocrystals of hydroxyapatite with needle and flake shapes as well as intermediate morphologies.

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Un tipo de biomasa pobre en lignina, del género Pennisetum, fue sometida al proceso de conversión hidrotérmica en presencia de carbonato de potasio como catalizador. Las reacciones se llevaron a cabo en ambientes cercanos al punto crítico del agua. Los productos de reacción no acuosos (biocrudo) se separaron por decantación y se analizaron por espectrometría infrarroja. Los biocrudos obtenidos contienen compuestos con funcionalidades aromáticas, olefínicas, hidroxiladas, éteres, y para el caso del biocrudo obtenido bajo la condición subcrítica funciones carbonilo. La fracción gaseosa y el biocrudo aumentan en presencia del carbonato de potasio.

A type of poor-lignin biomass (Pennisetum sp.) was hydrothermally converted in the presence of potassium carbonate as catalyst. The reactions were carried out close to the critical point of the water. The non-aqueous (biocrude) reaction products were separated by decantation and were analyzed by infrared spectrometry. The biocrude products so obtained contained compounds having aromatic, olephinic, hydroxylated and ether functionalities; sub-critical biocrude had carbonyl functions. The gaseous and biocrude fractions increased in the presence of potassium carbonate.

Um tipo de biomassa pobre em lenhina, do género Pennisetum, foi submetido ao processo de conversão hidrotérmica na presença de carbonato de potássio como catalisador. As reacções foram conduzidas em condições próximas do ponto crítico da água. Os produtos de reacção não aquosos (biopetróleo) foram separados por decantação e analisados por espectroscopia de infravermelho. Os biopetróleos obtidos contêm compostos com funcionalidades aromáticas, olefínicas, hidroxiladas, éteres e, no caso do biopetróleo obtido sob condição subcrítica, funções carbonilo. A fracção gasosa e a quantidade de biopetróleo aumentam na presença de carbonato de potássio.