Water-soluble Low Molecular Weight Research Articles

Effects of post-mortem aging process on characteristic water-soluble taste-active precursors in yellow-feathered broilers

Chilled chicken has become the mainstream of chicken consumption. In order to explore the effect of post-mortem aging on water-soluble flavor precursors of chicken, pH, adenosine triphosphate (ATP) degradation, flavor nucleosides, free amino acids and water-soluble low molecular weight peptides were determined using Qingyuan partridge yellow-feathered broilers as material during 0–4 °C post-mortem aging in 48 h. The results showed that the pH value fell to the limit pH 5.64 (4 h) in chicken breast and 6.21 (3 h) in thigh. Regardless of chicken breast or thigh, ATP dropped rapidly within 3 h. It was found that the K-value in chicken thigh was the lowest at 2 h indicating the freshness was the best. Considering the equivalent umami concentration (EUC), the value at 3 h and 4 h was relatively high, but the corresponding electronic tongue umami value was not high, which further showed that the water-soluble low molecular taste peptide played an important role on the post-mortem aging process. Combined with cluster analysis and partial least squares discriminant analysis (PLS-DA), it was preliminarily inferred that the optimal time for chilled chicken during 0–4 °C post-mortem aging was 2 h, which could provide a theoretical basis for the further processing of fresh chicken.

Influence of south Asian outflow on secondary organic aerosol formation over the Indian Ocean: Inferences from water-soluble low molecular weight dicarboxylic acids and related organic compounds during ICARB 2018 experiment

Low molecular weight dicarboxylic acids constituting a pivotal fraction of organic aerosols impact radiative forcing of Earth's atmosphere. However, a significant knowledge gap exists associated with their sources and formation pathways in the atmosphere. In this study, we report on water-soluble components such as dicarboxylic acids, oxoacids, and α-dicarbonyls as well as carbonaceous and ionic components in the continental outflow from the South Asian region to the Arabian Sea and the equatorial Indian Ocean during ICARB (Integrated Campaign for Aerosols, gases and Radiation Budget) 2018 experiment. Non-sea-salt sulfate (nss SO42−) was found to be the predominant component, followed by ammonium (NH4+) and organic carbon (OC) in fine-sized (<1.1 μm) aerosols. Total diacids carbon content accounted for 17% (on average) of total carbon (TC). Oxalic acid (C2) was the most abundant organic acid, contributing ~41% to total diacids, followed by terephthalic acid (tPh) and succinic acid (C4). Of these results, together with selected organic and inorganic mass ratios and linear relationships among the organic acids, we highlight the sources of organic acids over Indian Ocean. Over continental outflow regions in Indian Ocean, dicarboxylic acids are majorly derived from the emissions of biomass burning and combustion related sources, that underwent transformation in the atmosphere through photochemical reactions during the long range transport. However, over the deep oceanic environment of Indian Ocean, photo-oxidation of biogenic unsaturated fatty acids were found to be the important sources. The findings from this study will be helpful to improve further our understanding of the sources and formation processes of organic aerosols and their climate effects over the South Asian outflow regions.

Conformationally tunable calix[4]pyrrole-based nanofilms for efficient molecular separation

Preparation of nanofilms which are able to reject water-soluble low molecular weight organic compounds in nanofiltration remains to be a challenge. Herein, we report a new kind of self-standing, defect-free, robust, centimeter-sized and thickness controllable calix[4]pyrrole (C[4]P)-based nanofilms with excellent molecular sieving performance in nanofiltration. The nanofilms were prepared via confined dynamic condensation of the tetra-benzoyl-hydrazine derivative of calix[4]pyrrole (CPTBH) with 1,3,5-benzenetricarboxaldehyde (BTC) at the air/dimethyl sulfoxide (DMSO) interface. Nanofiltration tests under 2 bar pressure with porous polyethylene terephthalate (PET) as the support and a CsF treated CPTBH-BTC nanofilm (∼100 nm) as the selective layer depicted a water permeance of 15 L m-2h−1 bar−1 and a methanol permeance of 45 L m-2h−1 bar−1. High rejection rates (>95%) were found in aqueous solution for most of the tested dyes and pharmaceuticals. Remarkably, the composite membrane also demonstrated good separation performance in aqueous phase to some amino acids and organic dyes with molecular weights around 200 g/mol. High-performance nanofiltration in methanol was also realized. In this case, the molecular weight cutoff value is ∼ 800 g/mol. These findings showed that introduction of macrocyclic hosts is an effective way to develop nanofilms with high solvent permeance but low molecular weight cutoff value.

Complexation of tannic acid with polyoxypropylene diamine in water and application for the preparation of hierarchically structured functional surfaces

We rationalize that a water-soluble low molecular weight polyoxypropylene diamine (i.e., Jeffamine® D400 polyetheramine), capable of various types of noncovalent molecular interactions through its amine and propylene oxide groups, presents a simple yet versatile opportunity to form complexes with natural polyphenol of tannic acid (TA) and be exploited to engineer functional materials and surfaces. By investigating TA-D400 complexation behaviors in water, we demonstrate that mixing weakly acidic TA and neutral D400 solutions of stock concentrations above 1.0 mg/mL allowed easy formation of colloidally stable TA-D400 complexes. Such complexes were characterized as cationic nanoparticles of typical hydrodynamic diameters less than 300 nm. Mixing ratios were found to be less of an influencer on complexation. The TA-D400 intermolecular complexation was shown to be driven primarily by hydrophobic interaction in conjunction with ionic association. A simple immersion process can induce the formation of substrate-independent, hierarchically structured, and highly hydrophilic surfaces because of adsorption of TA-D400 complexes. Such functional surfaces not only can potentially modulate cell-material interactions shown by our brief in vitro fibroblast cell culture study, but also are feasible for in situ facile reduction of HAuCl4 to achieve integration of gold nanoparticles for function enrichment. This TA-D400 system adds a new option to the toolbox of polyphenol-mediated green technologies for surface engineering.

Changes in physicochemical properties and water‐soluble small molecular compounds of dry‐cured Xuanwei ham during processing

Thirty experimental Xuanwei hams were processed by a traditional method using green hams from local Xuanhe pigs of Xuanwei, Yunnan province, PR China. Samples of Biceps femoris were collected from six hams randomly at the five key processing stages, that is green ham, salting, air drying, aging for 3 months, and aging for 7 months. Physicochemical properties and water-soluble small molecular (WSSM) compounds change during the processing period of Xuanwei ham were evaluated. Moisture contents, water activity, and total nitrogen contents (TN) decreased significantly (p < .05). On the contrary, chloride content, weight loss rate, non-protein nitrogen content (NPN), and the protein hydrolysis index (P.I.) were observed a significant increase during the processing. The WSSM compounds in various processing stages of Xuanwei ham were analyzed by proton nuclear magnetic resonance (1H-NMR) technology. A total of 54 WSSM compounds were found, consisting of 26 amino acids and their derivatives, 10 organic acids, 6 nucleic acids, 4 amines and ammonia compounds, 3 alcohols, 2 sugars, and 3 other WSSM compounds. After aging for 7 months, the content of free amino acids in hams reached 58.93 mg/g, and the main amino acids were glutamic acid and alanine. In this study, the physicochemical properties of Xuanwei ham were evaluated effectively, which provided the basis for the quality control of Xuanwei ham. Practical applications Dry-cured Xuanwei ham is a traditional fermented meat product in Yunnan province of southwest China. The aim of this study was to determine the changes in physicochemical properties and water-soluble low molecular weight compounds of dry-cured Xuanwei ham during the production process. Our findings thus provide a theoretical analysis on the quality changes of dry-cured Chinese Xuanwei ham during processing. The results of this study can provide important theoretical basis for further study on protein degradation mechanism and characteristic flavor formation of Xuanwei ham.

Optical Method and Biochemical Source for the Assessment of the Middle-Molecule Uremic Toxin β2-Microglobulin in Spent Dialysate.

Optical monitoring of spent dialysate has been used to estimate the removal of water-soluble low molecular weight as well as protein-bound uremic toxins from the blood of end stage kidney disease (ESKD) patients. The aim of this work was to develop an optical method to estimate the removal of β2-microglobulin (β2M), a marker of middle molecule (MM) uremic toxins, during hemodialysis (HD) treatment. Ultraviolet (UV) and fluorescence spectra of dialysate samples were recorded from 88 dialysis sessions of 22 ESKD patients, receiving four different settings of dialysis treatments. Stepwise regression was used to obtain the best model for the assessment of β2M concentration in the spent dialysate. The correlation coefficient 0.958 and an accuracy of 0.000 ± 0.304 mg/L was achieved between laboratory and optically estimated β2M concentrations in spent dialysate for the entire cohort. Optically and laboratory estimated reduction ratio (RR) and total removed solute (TRS) of β2M were not statistically different (p > 0.35). Dialytic elimination of MM uremic toxin β2M can be followed optically during dialysis treatment of ESKD patients. The main contributors to the optical signal of the MM fraction in the spent dialysate were provisionally identified as tryptophan (Trp) in small peptides and proteins, and advanced glycation end-products.

Asterias pectinifera derived collagen peptide-encapsulating elastic nanoliposomes for the cosmetic application

Asterias pectinifera, a starfish that has been known to ruin the aquaculture industry owing to its voracious appetite, has recently been identified as an eco-friendly source of non-toxic and highly water-soluble low-molecular weight collagen peptides, which promotes wound healing, bone regeneration, and skin protection. Although they have potential applications in biomedical applications, including pharmaceuticals and cosmetic products, it remains unclear how to improve the in vivo absorption of collagen peptides. Here, we present a novel method to enhance the absorption rate of collagen peptides using a lipid-based nanocarrier. We prepared an elastic nanoliposome by controlling the composition ratio of phospholipids and low-molecular weight collagen peptides. Our results indicate that low-molecular weight collagen peptides extracted from Asterias pectinifera have higher encapsulation efficiency than the collagen peptides extracted from pork and fish, which have traditionally been considered as a conventional source of collagen. Moreover, we demonstrate that the elastic nanoliposome containing the collagen peptide of Asterias pectinifera can reduce MMP-1 expression caused by ultraviolet radiation-induced photoaging. Therefore, the combination of Asterias pectinifera-derived low-molecular-weight collagen peptides and elastic nanoliposomes may be a promising formulation as an eco-friendly source of materials for anti-aging cosmetics.

Anti-inflammatory activity of soluble chito-oligosaccharides (CHOS) on VitD3-induced human THP-1 monocytes.

Chito-oligosaccharides (CHOS) are oligomers of D-glucosamine and N-acetyl-glucosamine. Anti-inflammatory activities of a wide variety of CHOS mixtures have previously been reported, mainly based on studies with mouse models and murine macrophages. Since the mouse and human immune systems are quite different, gaining insight into the activity of CHOS on human cell lines, using well-characterized CHOS mixtures, is of considerable interest. Bacillus subtilis chitosanase (BsCsn46A) can efficiently convert chitosan to mixtures of water soluble low molecular weight CHOS. Here, the anti-inflammatory activity of a properly characterized CHOS mixture was studied, using human THP-1 cells that were differentiated to mature monocytes using vitamin D3. Addition of CHOS reduced the production of multiple pro-inflammatory cytokines associated with bacterial lipopolyssacharide (LPS)-stimulated inflammation, in a dose-dependent manner and without affecting cell viability. Interestingly, only minimal effects of CHOS were observed in similar experiments with phorbol 12-myristate 13-acetate- (PMA-) differentiated, macrophage-like, THP-1 cells. Altogether, in addition to showing promising biological effects of well-characterized low molecular weight soluble CHOS in a human system, the present study also points at Vitamin D3-stimulated THP-1 cells as a favorable system for assessing the anti-inflammatory activity of bioactive compounds.

Encapsulation of polyprodrugs enables an efficient and controlled release of dexamethasone.

Water-soluble low molecular weight drugs, such as the synthetic glucocorticoid dexamethasone (DXM), can easily leak out of nanocarriers after encapsulation due to their hydrophilic nature and small size. This can lead to a reduced therapeutic efficacy and therefore to unwanted adverse effects on healthy tissue. Targeting DXM to inflammatory cells of the liver like Kupffer cells or macrophages is a promising approach to minimize typical side effects. Therefore, a controlled transport to the cells of interest and selective on-site release is crucial. Aim of this study was the development of a DXM-phosphate-based polyprodrug and the encapsulation in silica nanocontainers (SiO2 NCs) for the reduction of inflammatory responses in liver cells. DXM was copolymerized with a linker molecule introducing pH-cleavable hydrazone bonds in the backbone and obtaining polyprodrugs (PDXM). Encapsulation of PDXMs into SiO2 NCs provided a stable confinement avoiding uncontrolled leakage. PDXMs were degraded under acidic conditions and subsequently released out of SiO2 NCs. Biological studies showed significantly enhanced anti-inflammatory capacity of the polyprodrug nanoformulations over non-encapsulated DXM or soluble polyprodrugs. These results demonstrate the advantage of combining the polyprodrug strategy with nanocarrier-mediated delivery for enhanced control of the delivery of water-soluble low molecular weight drugs.

1H NMR-based water-soluble lower molecule characterization and fatty acid composition of Chinese native chickens and commercial broiler

The aim of this study was to compare the water-soluble low molecular weight (WLMW) compounds and fatty acids (FAs) in raw meat and chicken soup between the two Chinese native chickens (Wuding chicken and Yanjin silky fowl chicken) and one typical commercial broiler (Cobb chicken). The WLMW compounds of chicken meat was studied using 1H nuclear magnetic resonance spectroscopy (1H NMR) and the FAs were identified and quantified using gas chromatography-mass spectrometry (GC–MS). Compared with typical commercial broiler, the main flavor substances (WLMW compounds and FAs) content were significantly higher in the breast and leg meat of the two Chinese native chickens (P < 0.05). Instead, the content of main flavor compounds was significantly higher in chicken soup of typical commercial broiler (P < 0.05). These results contribute to a further understanding the distinction of the flavor compounds between the typical commercial broiler and Chinese native chickens, which could be used to help assess the meat quality of different local broilers.

Analysis of flavor-related compounds in four edible wild mushroom soups

Four edible wild mushrooms, ie., Tuber aestivum, Cantharellus cibarius, Tricholoma matsutake and Boletus edulis were used as experiment materials to cook soup, and the difference of flavor profiles among the four soups were observed. Sensory evaluation results showed that C. cibarius soup had the highest score. The content of total fatty acids was the most in T. matsutake soup. Palmitic, stearic, oleic and linoleic acids were the main in four soups. The water-soluble low molecular weight (WSLMW) components from four soups were detected by liquid chromatography-mass spectrometry (LC-MS) based metabolomics approach, and then betaine, isopentenyladenine, choline and other 11 differential WSLMW components were screened out. 41 volatile compounds were identified by gas chromatography-ion mobility spectrometry (GC-IMS) coupled with multivariate statistical analysis, and the profiles of volatile compounds were obviously different among the four soups. Every studied soup had a unique taste, which could be completely distinguished by the electronic-tongue (ET).

Cold atmospheric pressure plasma treatment for adhesion improvement on polypropylene surfaces

Cold atmospheric pressure plasma from a plasma jet was used to improve the adhesion properties of polypropylene (PP). Differences in adhesion were at first observed for either air or N2 as process gas, tested on a PP-acrylic pressure sensitive adhesive (PSA) model system. For a deeper understanding changes in the surface chemistry and topography on PP after plasma jet treatment, using several different O2/N2 mixtures, were investigated in a comprehensive surface analytical study. Independent of the gas composition a majority of plasma induced polar groups exist as water soluble low molecular weight oxidized material (LMWOM), located within the first few nanometers. Consequently, the observed changes in the surface chemistry for various process gas compositions are mainly attributed to differences in the formed LMWOM. However, these chemical changes indicated also differences in the interaction mechanism of plasma reactive species with the polymer surface and therefore, in the resulting plasma-polymer etching process. Hence, significant changes in the topography have been observed for different process gas compositions, which could be reliably correlated with the obtained adhesion results.

Changes in physicochemical parameters, free fatty acid profile and water‐soluble compounds of Yunnan dry‐cured beef during processing

In this work, proton nuclear magnetic resonance spectroscopy (1H-NMR）and gas chromatography–mass spectrometry was used to characterize the different metabolites and the free fatty acid composition of Yunnan dry-cured beef. Compared with raw meat, the moisture content of the finished product was reduced by 53.41% (p < .01). The water activity of the finished product was 15.15% lower than that of the raw beef (p < .05). The TBARS value reached its highest value during the first drying phase, 13 times higher than that of the raw meat (p < .01). The content of polyunsaturated fatty acids, monounsaturated fatty acids, and saturated fatty acids increased during the production. 1H-NMR was used to identify and quantify 59 water-soluble low molecular weight (WSLMW) compounds. Amino acids and its derivatives and amine compounds were the most abundant WSLMW compounds in the final product. The five compounds of lactate, creatine, carnosine, inosine monophosphate, and inosine play an important role in the differentiation of samples at different processing stages. Practical applications Yunnan dry-cured beef is a traditional naturally fermented meat product in Yunnan Hui Autonomous Region of China, which is famous for its unique flavor. At present, there are few studies on the change of flavor precursors in Yunnan dry-cured beef during processing, and the mechanism of flavor formation is still unclear. For these reasons, the aim of this study was to determine the changes in physicochemical parameters, free fatty acid profile, and water-soluble low molecular weight (WSLMW) compounds of Yunnan dry-cured beef during the production process. These results contribute to a more accurate understanding of precursor changes and flavor formation of Yunnan dry-cured beef during processing.

Water-soluble low molecular weight organics in cloud water at Mt. Tai Mo Shan, Hong Kong

Cloud-water samples collected at the summit of Mt. Tai Mo Shan (Mt. TMS, 957 m, a.s.l.), Hong Kong in autumn 2016 and spring 2017 were measured for molecular compositions and stable carbon isotope ratios (δ13C) of dicarboxylic acids, oxoacids and α-dicarbonyls. Oxalic acid (C2, 253–1680 μg L−1) was found as the most abundant diacid, followed by succinic acid (C4, 24–656 μg L−1) in autumn and phthalic acid (Ph, 27–363 μg L−1) in spring. Higher concentrations of Ph (192 ± 197 μg L−1) and terephthalic acid (tPh, 31 ± 15 μg L−1) were observed in autumn than those in spring, illustrating the enhanced contribution from fossil fuel combustion and plastic wastes burning. Stronger correlations for the shorter chain diacids (C2–C4) with NO3−, nss-SO42− and nss-K+ in autumn (R2 ≥ 0.7) than spring suggested that these diacids were mainly produced via atmospheric photooxidation following anthropogenic emissions. The δ13C values of C2 (mean − 14.7‰), glyoxylic acid (ωC2, −12.2‰), pyruvic acid (Pyr, −15.5‰), glyoxal (Gly, −13.5‰) were much higher than those in atmospheric aerosols from isoprene and other precursors, indicating that diacids, oxoacids and α-dicarbonyls in cloud at Mt. TMS were significantly influenced by photochemical formation during the long-range atmospheric transport.

1H-NMR-based water-soluble low molecular weight compound characterization and free fatty acid composition of five kinds of Yunnan dry-cured hams

The aim of this study was to characterize the chemical composition of flavor precursor for five kinds of Yunnan dry-cured hams (Xuanwei, Nuodeng, Sanchuan, Heqing, and Saba ham). The water-soluble low molecular weight (WLOM) compound profiles of the hams were characterized using proton nuclear magnetic resonance spectroscopy (1H-NMR), and the free fatty acid compositions were analyzed using gas chromatography–mass spectrometry (GC-MS). In total, 48 WLOM compounds were identified, including amino acids, amino acids derivatives, organic acids, nucleic acids, vitamins, sugars, alcohols and small peptides. In addition, 16 free fatty acid compounds were detected. Compared with the other four hams, the Sanchuan ham had the highest total WLOM compounds and free fatty acid contents (P < 0.05). Comprehensive multivariate data analysis showed that free amino acids (FAAs) are the main metabolites, and FAAs accounted for about 53.45%–59.71% of the total WLOM compounds for five kinds of Yunnan dry-cured hams. These results contribute to a better understanding of quality differences in dry-cured ham.

Determining binding of polycyclic aromatic hydrocarbons to CTABr micelles using semi-equilibrium dialysis techniques

Micellar enhanced ultrafiltration (MEUF) has been shown to be an effective removal technique for a variety of trace contaminants in wastewater, especially for water soluble low molecular weight organic contaminants. In MEUF, contaminants first partition into surfactant micelles prior to removal by ultrafiltration, where the contaminants are below the molecular weight cut-off of the ultrafiltration membrane but the micelles are above the cut-off. Binding constants of selected Polycyclic aromatic hydrocarbons (PAHs) such as naphthalene, phenanthrene, pyrene and fluorene have been determined in order to examine the removal efficiency of MEUF for PAHs with Cetyltrimethylammonium bromide (CTABr) using a semi equilibrium dialysis method. PAHs show strong binding with CTABr because of hydrophobic interactions. Our results enabled us to develop a relationship between binding constant (log KB) and log KOW for neutral compounds, which will be useful for predicting MEUF performance for PAHs removal from waste water. The range of our reported binding constant values are from 2.61 to 5.07.

Radiation Degradation of β-Glucan Extracted from Brewer’s Yeast for Enhancing Growth Promotion and Immunostimulant Activities on Broilers

Water-soluble low molecular weight β-glucan (WSLMG) was successfully prepared via γ-irradiation of insoluble β-glucan extracted from brewer’s yeast cell walls. The WSLMG content in an irradiated sample increased as the irradiation dose increased. The WSLMGs with a molecular weight (Mw) of 49, 25, and 11 kDa, obtained at correlative doses of 100, 200, and 300 kGy, respectively, were tested using growth promotion and immune stimulant effects in broilers. Supplementation with 500 ppm WSLMGs not only increased the survival rate (33.3%) and average body weight (40%) but also reduced the feed conversion rate (35.4%) in tested broilers. In addition, WSLMGs enhanced both nonspecific and specific immune components in the blood of supplemented broilers. The WSLMG with Mw ~25 kDa showed the highest effect on the growth performance and immunomodulatory capability in the immune systems of the tested broilers. In conclusion, this product demonstrates substantial promise as an immunostimulant and growth-promoting additive for poultry.

1 H-NMR-based water-soluble low molecular weight compound characterization and fatty acid composition of boiled Wuding chicken during processing.

Boiled Wuding chicken was produced using whole chicken by washing, boiling 1 h with salt, deep frying, and boiling 2 h. The effect of the process on the water-soluble low molecular weight (WLOM) compound profiles of products was characterized using proton nuclear magnetic resonance spectroscopy, and the fatty acid composition of products was analyzed using gas chromatography-mass spectrometry. The metabolome was dominated by 49 WLOM compounds, and 22 fatty acid compounds were detected. Principal component (PC)1 and PC2 explained a total of 93.4% and 3% of variance respectively. Compared with the control group, the total WLOM compound and fatty acid contents of the chicken breast were significantly decreased in the other three processing stages (P<0.05). Comprehensive multivariate data analysis showed significant differences about precursor substance between the different processing including creatine, lactate, creatinine, glucose, taurine, anserine, and acetate (P<0.05). These results contribute to a more accurate understanding of precursor substance changes of flavor in chicken meat during processing. Boiled, treated chicken had significant effects on fatty acid and WLOM compounds. © 2018 Society of Chemical Industry.

Structure and Bioactivity Screening of a Low Molecular Weight Ulvan from the Green Alga Ulothrix flacca.

A water-soluble low molecular–weight polysaccharide named UP2-1 was isolated and purified from the marine green algae Ulothrix flacca using ion-exchange and size-exclusion chromatography. Composition and characteristics analyses showed that UP2-1 was a sulfated glucuronorhamnan consisting of rhamnose and glucuronic acid in a ratio of 2:1 with 21% sulfate content and a molecular weight of 5.0 kDa. Structural properties were determined using desulfation and methylation analyses combined with infrared spectrum (IR), gas chromatography-mass spectrometer (GC-MS) and nuclear magnetic resonance (NMR). The results showed that UP2-1 was a type of ulvan composed of alternate 4-linked-α-L-rhamnose residues (→4)-α-L-Rha(1→) and 4-linked-β-D-glucouronoc acid residues. The sulfate groups were mainly present in the O-3 position of →4)-α-L-Rha(1→. Most (70%) of the rhamnose was sulfated. UP2-1 also had a small amount of →4)-α-L-Rha(1→ branch at the O-2 position of the →4)-α-L-Rha(1→. UP2-1 exhibited significant anticoagulant and immunomodulating activity in vitro. This study demonstrated that the green algae Ulothrix flacca, which is used as a food and traditional marine herb in China, could also be considered as a source of bioactive ulvan.

Total reducing capacity in Arabidopsis thaliana cat2cat3 knockout mutants under heat stress

Aim. It was investigated whether the simultaneous loss of the two catalase isoforms CAT2 and CAT3 can be compensated by the increase in content of low-molecular weight antioxidants. To clarify this question, the total reducing capacity in Arabidopsis wild type and cat2cat3 knockout mutants was evaluated under optimal growth conditions and after heat stress. Methods. Leaves of Arabidopsis thaliana wild type and cat2cat3 knockout mutants were exposed to high temperatures. The content of water-soluble low molecular weight antioxidants was evaluated by determining the total reducing capacity using iodometry. Results. In intact cat2cat3 mutants there is an 1.7 times increase in the content of low-molecular weight antioxidants compared to wild type plants. A high content of these compounds in knockout plants was also observed upon heat stress. Patterns of changes in total reducing capacity differ between wild type and knockout lines. Conclusion. The loss of activity of the catalase isoforms CAT2 and CAT3 in knock-out mutants of Arabidopsis results in activation of non-enzymatic antioxidant defenses. The increase of the content of low-molecular weight antioxidants is one of the mechanisms that provide protection of mutant plants from chronic oxidative stress, both under optimal cultivation conditions and under the influence of elevated temperatures.Keywords: multigenic family, heat shock, total reducing capacity, knockout mutants, Arabidopsis thaliana.