A proposed antioxidation mechanism of ergothioneine based on the chemically-derived oxidation product hercynine and further decomposition products

2021 ◽  
Author(s):  
Chika Ando ◽  
Yasujiro Morimitsu
Keyword(s):  
Hydrogen Peroxide ◽  
Oxidation Mechanism ◽  
Major Product ◽  
Oxidation Products ◽  
Liquid Chromatography Mass Spectrometry ◽  
Decomposition Products ◽  
Physiological Conditions ◽  
Chemical Oxidants ◽  
Mechanism Of Oxidation ◽  
Antioxidation Mechanism

Abstract Ergothioneine (ERGO), a thiohistidine betaine, exists in various fungi, plants, and animals. Humans take in ERGO from their diet. ERGO is a strong biological antioxidant, but there are only a limited number of reports about its redox mechanism. The purpose of this study was to clarify the oxidation mechanism of ERGO. Reactions of ERGO with chemical oxidants were performed. The oxidation products of ERGO were analyzed by nuclear magnetic resonance and liquid chromatography-mass spectrometry (LC-MS). The major product of oxidation of ERGO by hydrogen peroxide in physiological conditions was identified as hercynine (histidine betaine). One molecule of ERGO was able to reduce two molecules of hydrogen peroxide. Hercynine was found to react with the more potent oxidant hypochlorite. One unstable decomposition product was detected by LC-MS. As a result, a mechanism of oxidation of ERGO, and hence its physiological antioxidant activity, was developed.

Oxidation of Azo Dyes by Peroxidase: Additional Evidence of a One-Electron Mechanism of Oxidation of Dimethylaminoazobenzene and Sudan I (Solvent Yellow 14)

1996 ◽  
Vol 61 (6) ◽  
pp. 962-972 ◽  
Author(s):  
Marie Stiborová ◽  
Befekadu Asfaw ◽  
Eva Frei ◽  
Heinz H. Schmeiser
Keyword(s):  
Hydrogen Peroxide ◽  
Oxygen Consumption ◽  
Azo Dyes ◽  
Oxidation Mechanism ◽  
Sudan I ◽  
Unknown Structure ◽  
Acidic Conditions ◽  
Mechanism Of Oxidation ◽  
Ph Dependent ◽  
Aminoazo Dyes

In the presence of hydrogen peroxide, peroxidase oxidized aminoazo dyes, the non-aminoazo dye 1-phenylazo-2-hydroxynaphthalene (Sudan I, Solvent Yellow 14), and its C-hydroxy derivatives. The oxidation of azo dyes is a pH-dependent reaction; while slightly acidic conditions are optimal for the aminoazo dyes, a basic pH suits better for Sudan I and its hydroxy derivatives. The oxidation of the carcinogenic Sudan I and dimethylaminoazobenzene catalyzed by peroxidase was investigated in detail. Oxygen consumption was not observed in incubations of peroxidase, azo dyes and hydrogen peroxide. However, oxygen uptake was observed after the addition of glutathione, which indicates that free radical metabolites of these compounds are formed by peroxidase. The results suggest that peroxidase metabolizes Sudan I and dimethylaminoazobenzene through a one-electron oxidation mechanism, giving rise to free radicals. Three of the products of Sudan I oxidation by peroxidase with a hitherto unknown structure were characterized partly by UV/VIS and mass spectroscopy.

Catalytic Oxidation of Quinine Using Hydrogen Peroxide with Palladium as Catalyst

2021 ◽  
Vol 874 ◽  
pp. 69-74
Author(s):  
Nila Tanyela Berghuis ◽  
Yana Maolana Syah ◽  
Didin Mujahidin
Keyword(s):  
Hydrogen Peroxide ◽  
Catalytic Oxidation ◽  
Column Chromatography ◽  
Secondary Alcohol ◽  
Major Product ◽  
Oxidation Products ◽  
Palladium Chloride ◽  
Quinoline Moiety

The oxidation of quinine using hydrogen peroxide yielded quinine N-oxide as a major product. The reaction can be accelerated in the presence of palladium chloride (PdCl2) as catalyst. The trace products, however, were identified as the further oxidation products at quinoline moiety producing N-Oxide as a major product and the secondary alcohol at C-9 producing the ketone, furthermore the alkene translocation product. The trace products were successfully isolated and characterized by NMR protons and carbons. Purification of the product was performed by column chromatography.

Chemistry of the Podocarpaceae. XXXIV. Some oxidation products of (13R)-Labda-8(17),14-dien-13-ol (Manool)

1971 ◽  
Vol 24 (11) ◽  
pp. 2365 ◽  
Author(s):  
RC Cambie ◽  
KN Joblin ◽  
AF Preston
Keyword(s):  
Nucleophilic Substitution ◽  
Potassium Permanganate ◽  
Hydroxy Acid ◽  
Methyl Ketone ◽  
Major Product ◽  
Oxidation Products ◽  
Lithium Aluminium Hydride ◽  
Methyl Ketones ◽  
Sodium Dichromate ◽  
Lithium Aluminium

Some products from the oxidation of manool (3) are examined. Potassium permanganate gives, inter alia, the hitherto unreported compound (16) while sodium dichromate gives the methyl ketone (5) and, as the major product, a mixture of (Z)- and (E)-α,β-unsaturated aldehydes (21). Hypoiodite oxidation of the methyl ketone (5) gives the α-hydroxy acid (26) in addition to the expected acid (6). Products of nucleophilic substitution have also been obtained from the hypoiodite oxidation of the methyl ketones (9) and (37). Peracid oxidation of the methyl ketone (5) gives the epoxy acetate (41) which, on reduction with lithium aluminium hydride, affords the diol (7), from which the odoriferous oxide (30) can be prepared. Oxidations leading to formation of the dione (10) are investigated.

scholarly journals A facile and effective method for preparation of 2.5-furandicarboxylic acid via hydrogen peroxide direct oxidation of 5-hydroxymethylfurfural

2017 ◽  
Vol 19 (1) ◽  
pp. 11-16 ◽  
Author(s):  
Shuang Zhang ◽  
Long Zhang
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction Time ◽  
Oxidation Mechanism ◽  
Molar Ratio ◽  
Alkaline Condition ◽  
Optimal Parameters ◽  
Direct Oxidation ◽  
Reaction Parameters ◽  
Alkaline Conditions ◽  
Furandicarboxylic Acid

Abstract In this paper, 2,5-furandicarboxylic acid (FDCA) was efficiently prepared by the direct oxidation of 5-hydroxymethylfurfural (5-HMF) using hydrogen peroxide (H2O2) in alkaline conditions without any catalysts. The effects of reaction parameters on the process were systematically investigated and the optimal parameters were obtained as follows: molar ratio of 5-HMF:KOH:H2O2 was 1:4:8, reaction temperature and reaction time were determined as 70°C and 15 minutes, respectively. Under these conditions, the yield of FDCA was 55.6% and the purity of FDCA could reach 99%. Moreover, we have speculated the detailed oxidation mechanism of 5-HMF assisted by hydrogen peroxide in alkaline condition to synthesize FDCA.

scholarly journals Formation and sink of glyoxal and methylglyoxal in a polluted subtropical environment: observation-based photochemical analysis and impact evaluation

2020 ◽  
Vol 20 (19) ◽  
pp. 11451-11467
Author(s):  
Zhenhao Ling ◽  
Qianqian Xie ◽  
Min Shao ◽  
Zhe Wang ◽  
Tao Wang ◽  
...  
Keyword(s):  
Southern China ◽  
Oxidation Mechanism ◽  
Receptor Site ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Major Pathway ◽  
Mixing Ratios ◽  
Heterogeneous Processes ◽  
The Pearl River ◽  
Improved Model

Abstract. The dicarbonyls glyoxal (Gly) and methylglyoxal (Mgly) have been recognized as important precursors of secondary organic aerosols (SOAs) through the atmospheric heterogeneous process. In this study, field measurement was conducted at a receptor site in the Pearl River Delta (PRD) region in southern China, and an observation-based photochemical box model was subsequently applied to investigate the production and evolution of Gly and Mgly as well as their contributions to SOA formation. The model was coupled with a detailed gas-phase oxidation mechanism of volatile organic compounds (VOCs) (i.e., Master Chemical Mechanism, MCM, v3.2), heterogeneous processes of Gly and Mgly (i.e., reversible partitioning in aqueous phase, irreversible volume reactions and irreversible surface uptake processes), and the gas–particle partitioning of oxidation products. The results suggested that without considering the heterogeneous processes of Gly and Mgly on aerosol surfaces, the model would overpredict the mixing ratios of Gly and Mgly by factors of 3.3 and 3.5 compared to the observed levels. The agreement between observation and simulation improved significantly when the irreversible uptake and the reversible partitioning were incorporated into the model, which in total both contributed ∼ 62 % to the destruction of Gly and Mgly during daytime. Further analysis of the photochemical budget of Gly and Mgly showed that the oxidation of aromatics by the OH radical was the major pathway producing Gly and Mgly, followed by degradation of alkynes and alkenes. Furthermore, based on the improved model mechanism, the contributions of VOC oxidation to SOA formed from gas–particle partitioning (SOAgp) and from heterogeneous processes of Gly and Mgly (SOAhet) were also quantified. It was found that o-xylene was the most significant contributor to SOAgp formation (∼ 29 %), while m,p-xylene and toluene made dominant contributions to SOAhet formation. Overall, the heterogeneous processes of Gly and Mgly can explain ∼ 21 % of SOA mass in the PRD region. The results of this study demonstrated the important roles of heterogeneous processes of Gly and Mgly in SOA formation and highlighted the need for a better understanding of the evolution of intermediate oxidation products.

scholarly journals Oxidation of Cyclohexane to Cylohexanol and Cyclohexanone Over H4[a-SiW12O40]/TiO2 Catalyst

2018 ◽  
Vol 16 (2) ◽  
pp. 175 ◽  
Author(s):  
Aldes Lesbani ◽  
Fatmawati Fatmawati ◽  
Risfidian Mohadi ◽  
Najma Annuria Fithri ◽  
Dedi Rohendi
Keyword(s):  
Hydrogen Peroxide ◽  
Ftir Spectroscopy ◽  
Mild Condition ◽  
Heterogeneous System ◽  
Pattern Analysis ◽  
Major Product ◽  
Ftir Spectrum ◽  
Powder Pattern ◽  
X Ray ◽  
Tio2 Catalyst

Oxidation of cyclohexane to cyclohexanol and cyclohexanone was carried out using H4[a-SiW12O40]/TiO2 as catalyst. In the first experiment, catalyst H4[a-SiW12O40]/TiO2 was synthesized and characterized using FTIR spectroscopy and X-Ray analysis. In the second experiment, catalyst H4[a-SiW12O40]/TiO2 was applied for conversion of cyclohexane. The conversion of cyclohexane was monitored using GC and GCMS. The results showed that H4[a-SiW12O40]/TiO2 was successfully synthesized using 1 g of H4[a-SiW12O40] and 0.5 g of TiO2. The FTIR spectrum showed vibration of H4[a-SiW12O40] appeared at 771-979 cm-1 and TiO2 at 520-680 cm-1. The XRD powder pattern analysis indicated that crystallinity of catalyst still remained after impregnation to form H4[a-SiW12O40]/TiO2. The H4[a-SiW12O40]/TiO2 catalyst was used for oxidation of cyclohexane in heterogeneous system under mild condition at 2 h, 70 °C, 0.038 g catalyst, and 3 mL hydrogen peroxide to give cyclohexanone as major product.

scholarly journals Mainz Isoprene Mechanism 2 (MIM2): an isoprene oxidation mechanism for regional and global atmospheric modelling

2008 ◽  
Vol 8 (4) ◽  
pp. 14033-14085 ◽  
Author(s):  
D. Taraborrelli ◽  
M. G. Lawrence ◽  
T. M. Butler ◽  
R. Sander ◽  
J. Lelieveld
Keyword(s):  
Atmospheric Chemistry ◽  
Oxidation Mechanism ◽  
Tropospheric Chemistry ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Good Representation ◽  
Chemical Production ◽  
Global Models ◽  
Mixing Ratios ◽  
Isoprene Oxidation

Abstract. We present an oxidation mechanism of intermediate size for isoprene (2-methyl-1,3-butadiene) suitable for simulations in regional and global atmospheric chemistry models, which we call MIM2. It is a reduction of the corresponding detailed mechanism in the Master Chemical Mechanism (MCM v3.1) and intended as the second version of the well-established Mainz Isoprene Mechanism (MIM). Our aim is to improve the representation of tropospheric chemistry in regional and global models under all NOx regimes. We evaluate MIM2 and re-evaluate MIM through comparisons with MCM v3.1. We find that MIM and MIM2 compute similar O3, OH and isoprene mixing ratios. Unlike MIM, MIM2 produces small relative biases for NOx and organic nitrogen-containing species due to a good representation of the alkyl and peroxy acyl nitrates (RONO2 and RC(O)OONO2). Moreover, MIM2 computes only small relative biases with respect to hydrogen peroxide (H2O2), methyl peroxide (CH3OOH), methanol (CH3OH), formaldehyde (HCHO), peroxy acetyl nitrate (PAN), and formic and acetic acids (HCOOH and CH3C(O)OH), being always below ≈6% in all NOx scenarios studied. Most of the isoprene oxidation products are represented explicitly, including methyl vinyl ketone (MVK), methacrolein (MACR), hydroxyacetone and methyl glyoxal. MIM2 is mass-conserving with respect to carbon, including CO2 as well. Therefore, it is suitable for studies assessing carbon monoxide (CO) from biogenic sources, as well as for studies focused on the carbon cycle. Compared to MIM, MIM2 considers new species like acetaldehyde (CH3CHO), propene (CH2=CHCH3) and glyoxal (CHOCHO) with global chemical production rates for the year 2005 of 7.3, 9.5 and 33.8 Tg/yr, respectively. Our new mechanism is expected to substantially improve the results of atmospheric chemistry models by more accurately representing the interplay between atmospheric chemistry, transport and deposition, especially of nitrogen reservoir species. MIM2 allows regional and global models to easily incorporate new experimental results on the chemistry of organic species.

Oxidation of Some Titanium Alloys in Air at Elevated Temperatures

2008 ◽  
Vol 595-598 ◽  
pp. 967-974 ◽  
Author(s):  
E. Godlewska ◽  
M. Mitoraj ◽  
B. Jajko
Keyword(s):  
Thermal Cycling ◽  
Titanium Alloys ◽  
Constant Temperature ◽  
Cross Sections ◽  
Elevated Temperatures ◽  
Mixed Oxides ◽  
Oxidation Mechanism ◽  
Testing Procedure ◽  
Oxidation Products ◽  
Outward Diffusion

This paper presents comparative studies on the performance of two titanium alloys (Ti- 6Al-1Mn, Ti-45.9Al-8Nb) in an oxidizing atmosphere at 700 oC and 800 oC. Testing procedure comprised thermogravimetric measurements at a constant temperature and in thermal cycling conditions (1-h and 20-h cycles at constant temperature followed by rapid cooling). The overall duration of the cyclic oxidation tests was up to 1000 hours. The oxidized specimens were analyzed in terms of chemical composition, phase composition, and morphology (SEM/EDS, TEM/EDS, XRD). The extent and forms of alloy degradation were evaluated on the basis of microscopic observation of specimen fractures and cross-sections. Selected specimens were examined by means of XPS, SIMS and GDS. Oxidation mechanism of Ti-46Al-8Nb was assessed a two-stage oxidation method using oxygen-18 and oxygen-16. Apparently, the oxidation of this alloy proceeded in several stages. According to XPS, already after quite short reaction time, the specimens were covered with a very thin oxide film, mainly composed of aluminum oxide (corundum). A thicker layer of titanium dioxide (rutile) developed underneath. These two layers were typical of the oxidation products formed on this alloy, even when tested in thermal cycling conditions. In general, the scale had a complex multilayer structure but it was thin and adherent. Under the continuous layer of titania, there was a fine-grained zone composed of mixed oxides. The alloy/scale interface was marked with niobium-rich precipitates embedded in a titanium-rich matrix. There were some indications of secondary processes occurring under the initial continuous oxide layers (e.g. characteristic layout of pores or voids). Thickness of inner scale layers clearly increased according to parabolic kinetics, while that of the outer compact layer (mainly TiO2) changed only slightly. The distribution of oxygen isotopes across the scale/alloy interface indicated two-way diffusion of the reacting species – oxygen inward and metals outward diffusion. Silicon deposited on Ti-6Al-1Mn alloy positively affected scale adhesion and remarkably reduced alloy degradation rate.

Production of Carboxymethyl Starches from Oxidized Starches and Determination of Their Tanning Characteristics

2021 ◽  
Vol 116 (6) ◽  
Author(s):  
Cigdem Kilicarislan Ozkan ◽  
Hasan Ozgunay
Keyword(s):  
Hydrogen Peroxide ◽  
Molecular Weight ◽  
Water Solubility ◽  
Good Alternative ◽  
Oxidation Products ◽  
Sodium Metaperiodate ◽  
Carboxymethyl Starch ◽  
Present Part

Hydrogen peroxide and sodium metaperiodate oxidation of starch and their possible utilization in tanning/retanning were examined in our previous studies. In the present part, accordingly with our previous findings, hydrogen peroxide and sodium metaperiodate oxidation products having appropriate molecular weight/size were selected and additionally carboxymethylated. The yields of the processes (carboxymethyl starches) were characterized comprehensively and the effect of carboxymethylation process on structures and tanning abilities were tried to be identified. The characterization results revealed that the carboxymethyl groups were successfully included into the structure and the water solubility of oxidized starches (especially periodate oxidized ones) increased by carboxymethylation process. From the evaluation of the tanning results and considering its properties i.e. gentle tanning effect with less astringency and correspondingly a relatively soft leather handle and smooth grain, it is concluded that dialdehyde carboxymethyl starch (CMS 1:0.7) can be utilized as yet another good alternative sustainable green tanning/retanning agent from starch.

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