Investigating the scavenging of reactive oxygen species by antioxidants via theoretical and experimental methods

Coordinated wound responses in a regenerative animal-algal holobiont

Animal regeneration involves coordinated responses across cell types throughout the animal body. In endosymbiotic animals, whether and how symbionts react to host injury and how cellular responses are integrated across species remain unexplored. Here, we study the acoel Convolutriloba longifissura, which hosts symbiotic Tetraselmis sp. green algae and can regenerate entire bodies from tissue fragments. We show that animal injury causes a decline in the photosynthetic efficiency of the symbiotic algae, alongside two distinct, sequential waves of transcriptional responses in acoel and algal cells. The initial algal response is characterized by the upregulation of a cohort of photosynthesis-related genes, though photosynthesis is not necessary for regeneration. A conserved animal transcription factor, runt, is induced after injury and required for acoel regeneration. Knockdown of Cl-runt dampens transcriptional responses in both species and further reduces algal photosynthetic efficiency post-injury. Our results suggest that the holobiont functions as an integrated unit of biological organization by coordinating molecular networks across species through the runt-dependent animal regeneration program.

Stimuli-responsive nanoparticles delivered by a nasal-brain pathway alleviate depression-like behavior through extensively scavenging ROS

Depression is one of the most common mental diseases, which seriously affects patients' physical and mental health. Emerging evidence has indicated that oxidative stress (OS) is a major cause of neurodegeneration involved in the pathogenesis of depression. Consequently, targeted reactive oxygen species (ROS) elimination is regarded as a promising strategy for efficient depression therapy. In addition, insufficient brain drug delivery is the main obstacle to depression therapy owing to the presence of the blood-brain barrier (BBB). To achieve the goals of bypassing the BBB and promoting antioxidant therapy for depression, a broad-spectrum ROS scavenging NPs was rationally designed through a nasal-brain pathway developed for combined ROS scavenging and brain drug delivery. A hexa-arginine (R6) modified ROS-responsive dextran (DEX) derivate was synthesized for antidepressant olanzapine (Olz) and H2 donor amino borane (AB) loading to prepare Olz/RDPA nanoparticles (NPs). Subsequently, the NPs were dispersed into a thermoresponsive hydrogel system based on poloxamer. In vitro and in vivo results demonstrated that Olz/RDPA in situ thermoresponsive hydrogel system could effectively deliver NPs to the brain via the nasal-brain pathway and alleviate depression-like behaviors through combined ROS depletion and inhibition of 5-HT dysfunction of the oxidative stress-induced. The proposed ROS-scavenging nanotherapeutic would open a new window for depression treatment. STATEMENT OF SIGNIFICANCE: ROS is an innovative therapeutic target involving the pathology of depression whereas targeted delivery of ROS scavenging has not been achieved yet. In the current study, ROS-responsive nanoparticles (Olz/RDPA NPs) were prepared and dispersed in a thermosensitive hydrogel for delivery through the nasal-brain pathway for the treatment of depression. Sufficient ROS depletion and improvement of delivery capacity by the nasal-brain pathway effectively could reverse oxidative stress and alleviate depressive-like behavior. Collectively, these nanoparticles may represent a promising strategy for the treatment of depression.

Current Trends in Computational Quantum Chemistry Studies on Antioxidant Radical Scavenging Activity

The antioxidative nature of chemicals is now routinely studied using computational quantum chemistry. Scientists are constantly proposing new approaches to investigate those methods, and the subject is evolving at a rapid pace. The goal of this review is to collect, consolidate, and present current trends in a clear, methodical, and reference-rich manner. This paper is divided into several sections, each of which corresponds to a different stage of elaborations: preliminary concerns, electronic structure analysis, and general reactivity (thermochemistry and kinetics). The sections are further subdivided based on methodologies used. Concluding remarks and future perspectives are presented based on the remaining elements.

Seed Treatment with Illite Enhanced Yield and Nutritional Value of Soybean Sprouts

Soybean sprouts, a nutritional food product, can contribute to food security because they can be grown within a week and do not require sophisticated technology. The yield and quality of soybean sprouts are influenced by various factors, including seed priming and growing conditions. The objective of this study was to investigate the effects of seed soaking in different concentrations of illite, a clay mineral, on the yield and quality of soybean sprouts. Soybean seeds soaked in five concentrations (0.5%, 1%, 3%, 5%, and 10%, w/v) of illite or tap water for 8 h were named IP-0.5, IP-1, IP3, IP-5, IP-10, and control, respectively. The highest sprout yield was found in IP-3, followed by IP-1, and IP-5, which had 11.1%, 8.8%, and 7.4% increments, respectively, compared to the control. The content of vitamin C, mineral element, isoflavone, total polyphenol, and total flavonoid was higher in many of the illite-treated soybean sprouts than in the control. The overall results indicated that pre-soaking soybean seeds in lower concentrations (0.5-3%, w/v) of illite could be helpful to enhance the yield and nutritional value of soybean sprouts in an easy and inexpensive way.

Electronic structure analysis of riboflavin: OVGF and EOM-CCSD study

The computational simulation of the photoelectron spectrum of active form of vitamin B2 is reported in the gas phase. In this work, we determine relative stability of eight riboflavin conformers by conformational search first with molecular mechanics AMMP potential in VEGA software at 553 K. Relative abundance of conformers was deduced from Boltzmann population weighting method (BPW). The three most stable conformers were then selected for computing valence, vertical ionization energies. We used high-level Equation-of-Motion Coupled-Cluster (EOM-IP-CCSD) method to obtain valence ionization energies (IP). In order to characterize the nature of ionization processes pertaining to different spectral bands, natural bonding orbital (NBO) method and molecular electrostatic potentials (MEP) were used to obtain orbital electron densities. The influence of the electronic structure of riboflavin on its biological activity is manifested via reduction of ionization energies of outermost orbitals which makes electron densities of these orbitals more readily available to participate in ligand-receptor bonding.

Vitamin E Is Superior to Vitamin C in Delaying Seedling Senescence and Improving Resistance in Arabidopsis Deficient in Macro-Elements

Nitrogen (N), phosphorus (P), and potassium (K) are three essential macro-elements for plant growth and development. Used to improve yield in agricultural production, the excessive use of chemical fertilizers often leads to increased production costs and ecological environmental pollution. Vitamins C and E are antioxidants that play an important role in alleviating abiotic stress. However, there are few studies on alleviating oxidative stress caused by macro-element deficiency. Here, we used Arabidopsis vitamin E synthesis-deficient mutant vte4 and vitamin C synthesis-deficient mutant vtc1 on which exogenous vitamin E and vitamin C, respectively, were applied at the bolting stage. In the deficiency of macro-elements, the Arabidopsis chlorophyll content decreased, malondialdehyde (MDA) content and relative electric conductivity increased, and reactive oxygen species (ROS) accumulated. The mutants vtc1 and vte4 are more severely stressed than the wild-type plants. Adding exogenous vitamin E was found to better alleviate stress than adding vitamin C. Vitamin C barely affected and vitamin E significantly inhibited the synthesis of ethylene (ETH) and jasmonic acid (JA) genes, thereby reducing the accumulation of ETH and JA that alleviated the senescence caused by macro-element deficiency at the later stage of bolting in Arabidopsis. A deficiency of macro-elements also reduced the yield and germination rate of the seeds, which were more apparent in vtc1 and vte4, and adding exogenous vitamin C and vitamin E, respectively, could restore them. This study reported, for the first time, that vitamin E is better than vitamin C in delaying seedling senescence caused by macro-element deficiency in Arabidopsis.

Organogermanium suppresses cell death due to oxidative stress in normal human dermal fibroblasts

Reactive oxygen species (ROS) are very harmful to dermal cells, and it is thus important to develop cosmetics that protect the skin from ROS and other stimuli. Repagermanium is a synthetic water-soluble organogermanium polymer, and in this study, we attempted to visualize the incorporation of germanium into normal human dermal fibroblasts (NHDFs) using isotope microscopy. In addition, the content of 3-(trihydroxygermyl)propanoic acid (THGP), a hydrolyzed monomer of repagermanium, in NHDFs was determined through liquid chromatography mass spectrometry (LC-MS/MS), and the dose-dependent incorporation of THGP was confirmed. We then evaluated the preventive effects of THGP against ROS-induced NHDF death and confirmed the observed preventive effects through gene profiling and expression analysis. The addition of 0.59–5.9 mM THGP reduced cell death resulting from ROS damage caused by the reaction between xanthine oxidase and hypoxanthine and the direct addition of H₂O₂. Furthermore, this study provides the first demonstration that the effect of THGP was not due to the direct scavenging of ROS, which indicates that the mechanism of THGP differs from that of general antioxidants, such as ascorbic acid. The gene profiling and expression analysis showed that THGP suppressed the expression of the nuclear receptor subfamily 4 group A member 2 (NR4A2) gene, which is related to cell death, and the interleukin 6 (IL6) and chemokine (C-X-C motif) ligand 2 (CXCL2) genes, which are related to the inflammatory response. Furthermore, the production of IL6 induced by H₂O₂ was suppressed by the THGP treatment. Our data suggest that the preventive effect of THGP against ROS-induced cell death is not due to antioxidant enzymes or ROS scavenging.

The antioxidant activity and active sites of delphinidin and petunidin measured by DFT, in vitro chemical-based and cell-based assays

A computational DFT B3LYP method with 6-311G (d,p) basis set, the in vitro chemical-based and cellular antioxidant activity (CAA) assays were applied in this study to explain the structure-antioxidant activity relationships of delphinidin and petunidin. The compound molecular structures, spectral properties, frontier orbital energy, and transition state of delphinidin and petunidin were compared. In transition state, the result of the active site (O21-H32 and O22-H33) was consistent with the result of bond length. The frontier orbital theory results indicated that the probable antioxidant activity order was petunidin (0.09126 a.u.) > delphinidin (0.09175 a.u.), which agreed well with the cell-based antioxidant activity determined by CAA. However, the order of ABTS^•+ and DPPH radical scavenging activity was delphinidin > petunidin. Our study could help to provide a rational approach for the investigation of antioxidant activity of phytochemicals. PRACTICAL APPLICATIONS: As anthocyanins, delphinidin and petunidin with great antioxidant activity are widely found in various fruits and vegetables. However, there are many kinds of methods used to measure their antioxidant activity and the antioxidant mechanism which are not concrete and clear. Therefore, it is crucial to study the antioxidant actvity of anthocyanins utilizing the DFT method combined with in vitro chemical-based and cell-based assays. Our study could contribute not only to the elucidation of chemical mechanism of antioxidants and exploration the structural features in essence, but also to promote the further development of phytochemicals in the field of food chemistry and pharmacy.

Antioxidant Motifs in Flavonoids: O-H versus C-H Bond Dissociation

Flavonoids provide potential health benefits due to their antioxidant properties. The antioxidant activity of natural flavonoids is primarily exerted by phenolic hydroxyl groups; however, C-H bonds also contribute to these properties. In this study, the contributions of phenolic groups and C-H bonds to the antioxidant properties of 13 flavonoids were investigated by using the (RO)B3LYP/6-311++G(2df,2p)//B3LYP/6-311G(d,p) model chemistry in the gas phase and water and ethanol solvents. It was found that the C-H bonds have lower bond dissociation energies than O-H bonds in the 4-carbonyl and/or 3-hydroxyl group containing flavonoids and hence define antioxidant activity. The HOO· radical scavenging of the selected flavonoids is also investigated in detail through the potential energy surface, natural bond orbitals, and kinetic calculations. It was found that the favored radical scavenging mechanism of the flavonoids is hydrogen atom transfer, with the gas phase rate constants in the range of 7.23 × 103-2.07 × 109 L·mol-1·s-1. The results suggest that the flavonoids, isomelacacidin, isoteracacidin, melacacidin, and teracacidin, have antioxidant properties as high as typical phenolic compounds such as quercetin, trans-resveratrol, trolox, and ascorbic acid.

Antioxidant properties of citric acid interfere with the uricase-based measurement of circulating uric acid

BACKGROUND

Circulating uric acid (UA) is an important biomarker, not only in the detection and management of gout, but also in assessing the risk of related comorbidity. The impact of collection methods on clinical UA measurements has been the subject of limited study. After observing significant differences between UA concentrations of blood samples obtained by different collection tubes, we began examining the effects of exogenous tube components on measured UA concentrations. We aimed to: (1) demonstrate the variability in uricase-based UA measurements attributable to different collection methods and (2) identify factors influencing this variability.

METHODS

Blood samples from human subjects were collected using Serum Separator Tubes (SST tubes), Acid Citrate Dextrose (ACD) tubes, and Sodium Citrate (SC) tubes. Circulating UA concentrations were measured by chemistry analyzers utilizing the uricase method. Absorbance assays were run in order to determine the effects of citric acid, sodium citrate, and dextrose on measured absorbance in the presence of leuco crystal violet dye, hydrogen peroxide, and peroxidase. Statistical analyses-including Student's T tests and ANOVA-were used to compare results.

RESULTS

UA concentrations of blood samples collected in ACD tubes were significantly lower than those collected in SST tubes (P < 0.01). Samples collected in SC tubes trended towards lower UA measurements than samples collected in SST tubes, although this difference did not reach statistical significance (P = 0.06). Blood samples spiked with separate concentrations of sodium citrate (3.2 and 22.0 g/L), citric acid (8.0 g/L), and dextrose (24.5 g/L) demonstrated significantly lower UA measurements compared to controls (P < 0.01). Absorbance assays demonstrated that increasing concentrations of citric acid and sodium citrate-in the presence of leuco crystal violet, hydrogen peroxide, and peroxidase-decreased the amount of oxidized dye in the uricase method of UA measurement in a dose-dependent manner (P < 0.01). In contrast, dextrose did not significantly alter the amount of oxidized dye available.

DISCUSSION

Our results indicate that citric acid obstructs accurate uricase-based UA measurement, providing falsely low values. Citric acid, a known antioxidant, scavenges hydrogen peroxide, a key intermediate using the uricase method. By scavenging hydrogen peroxide, citric acid decreases the amount of oxidized leuco dye leading to falsely low UA measurements. Therefore, collection tubes, like ACD and SC tubes, which contain concentrations of citric acid or its conjugate base sodium citrate should not be used to measure circulating UA levels when utilizing uricase-based measurement methods.

Synthesis and antioxidant action of chitosan derivatives with amino-containing groups via azide-alkyne click reaction and N-methylation

Amino functionality has been paid growing attention in chemical modification of polysaccharides due to their potential biomedical applications. Here, the preparation of novel antioxidant materials based on chitosan derivatives bearing amino-containing groups equipped with 1,2,3-triazole and 1,2,3-triazolium by Cuprous-catalyzed azide-alkyne cycloaddition and N-methylation was described for the first time. The structural characteristics of the synthesized derivatives were examined by FTIR, ¹H NMR, and elemental analysis. The antioxidant activities of the chitosan derivatives were assessed in vitro. The results indicated that chitosan derivatives bearing 1,2,3-triazoles displayed superior antioxidant activity over pristine chitosan, especially against superoxide anion radical. Moreover, antioxidant efficiency of chitosan derivatives further enhanced after N-methylation of 1,2,3-triazole moieties with iodomethane, which is comparative to that of ascorbic acid. Notably, of all chitosan derivatives bearing 1,2,3-triazole or 1,2,3-triazolium moieties, acylhydrazine-functionalized and amino-functionalized chitosan showed the stronger antioxidant capacity than hydroxyl-modified chitosan at the test concentration. Besides, the cytotoxicities of them were also evaluated in vitro on HaCaT cells. These results suggested that amino and acylhydrazine-functionalized chitosan derivatives with 1,2,3-triazolium could be used as novel antioxidant biomaterials.