Maillard and Hydrolytic Reactions in Subcritical Water Extraction of Bioactive Compounds from Licorice

Exploring the bioactive potential of algae residue extract via subcritical water extraction: Insights into chemical composition and biological activity

Gelidium sesquipedale is valued in the Spanish agar industry, but its production generates substantial waste, often discarded despite its nutritional and bioactive content. Subcritical water extraction (SWE) at 175 °C and 50 bar for 130 min was performed on this waste after agar extraction, comparing it to conventional ethanol extraction. The SWE extract exhibited superior nutritional profile, including proteins (170.6 ± 1.0 mg/gfreeze-dried-extract), essential amino acids (18.1%), carbohydrates (148.1 ± 0.3 mg/gfreeze-dried-extract), total phenolic content (57 ± 7 mg-EqGA/gfreeze-dried-extract), and also containing Maillard reaction compounds, such as 5-hydroxymethylfurfural, furfural, 2-furanmethanol, 1-(2-furanyl)-ethanone, and 5-methyl-2-furfural, influencing color, aroma and flavor. This extract showed better antioxidant and anti-inflammatory properties than the conventional extract, and higher xanthine oxidase, tyrosinase, and acetylcholinesterase inhibition activities. Toxicological assessment on human cells indicated the safety of the SWE extract. Therefore, SWE technology offers a promising method to valorize G. sesquipedale residue, yielding a bioactive and nutrient-rich extract suitable for food and nutraceutical applications.

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.

Degradation kinetics of sugars (glucose and xylose), amino acids (proline and aspartic acid) and their binary mixtures in subcritical water: Effect of Maillard reaction

A systematic kinetic study was conducted in subcritical water medium in the temperature range from 150 to 200 °C for pure glucose, xylose, proline and aspartic acid as well as binary mixtures of sugars + amino acids to understand the reaction kinetics and interactions among biomass components and to discern the influence of Maillard reaction (MR) on the overall reaction kinetics. The main degradation products identified for glucose and xylose were the respective dehydration products, hydroxymethyl furfural and furfural, yielding an increasing solid residue with temperature (15.9 wt% at 200 °C) with an augmented heating value. The degradation of sugars and amino acids in binary systems was faster compared to pure compounds due to MR and the production of dehydration products was delayed when considering total sugar conversion. Higher relative reactivity in MR was observed for xylose over glucose showing also higher antioxidant activity.

Silver Nanoparticles and Glycyrrhiza glabra (Licorice) Root Extract as Modifying Agents of Hydrogels Designed as Innovative Dressings

The interest in the application of plant extracts as modifiers of polymers intended for biomedical purposes is constantly increasing. The therapeutical properties of the licorice root, including its anti-inflammatory and antibacterial activity, make this plant particularly promising. The same applies to silver nanoparticles showing antibacterial properties. Thus the main purpose of the research was to design hydrogel dressings containing both licorice root extract and nanosilver so as to obtain a system promoting wound regeneration processes by preventing infection and inflammation within the wound. The first step included the preparation of the plant extract via the solid-liquid extraction using the Soxhlet extractor and the synthesis of silver nanoparticles by the chemical reduction of silver ions using a sodium borohydride as a reducing agent. Subsequently, hydrogels were synthesized via photopolymerization and subjected to studies aiming at characterizing their sorption properties, surface morphology via scanning electron microscopy, and their impact on simulated physiological liquids supported by defining these liquids' influence on hydrogels' structures by FT-IR spectroscopy. Next, the tensile strength of hydrogels and their percentage elongation were determined. Performed studies also allowed for determining the hydrogels' wettability and free surface energies. Finally, the cytotoxicity of hydrogels towards L929 murine fibroblasts via the MTT reduction assay was also verified. It was demonstrated that developed materials showed stability in simulated physiological liquids. Moreover, hydrogels were characterized by high elasticity (percentage elongation within the range of 24-29%), and their surfaces were hydrophilic (wetting angles below 90°). Hydrogels containing both licorice extract and nanosilver showed smooth and homogeneous surfaces. Importantly, cytotoxic properties towards L929 murine fibroblasts were excluded; thus, developed materials seem to have great potential for application as innovative dressings.