Peroxide Compounds Research Articles

Transcription Factors That Defend Bacteria Against Reactive Oxygen Species.

Bacteria live in a toxic world in which their competitors excrete hydrogen peroxide or superoxide-generating redox-cycling compounds. They protect themselves by activating regulons controlled by the OxyR, PerR, and SoxR transcription factors. OxyR and PerR sense peroxide when it oxidizes key thiolate or iron moieties, respectively; they then induce overlapping sets of proteins that defend their vulnerable metalloenzymes. An additional role for OxyR in detecting electrophilic compounds is possible. In some nonenteric bacteria, SoxR appears to control the synthesis and export of redox-cycling compounds, whereas in the enteric bacteria it defends the cell against the same agents. When these compounds oxidize its iron-sulfur cluster, SoxR induces proteins that exclude, excrete, or modify them. It also induces enzymes that defend the cell against the superoxide that such compounds make. Recent work has brought new insight into the biochemistry and physiology of these responses, and comparative studies have clarified their evolutionary histories.

Upregulation of Cysteine Synthase and Cystathionine β-Synthase Contributes to Leishmania braziliensis Survival under Oxidative Stress.

Cysteine metabolism is considered essential for the crucial maintenance of a reducing environment in trypanosomatids due to its importance as a precursor of trypanothione biosynthesis. Expression, activity, functional rescue, and overexpression of cysteine synthase (CS) and cystathionine β-synthase (CβS) were evaluated in Leishmania braziliensis promastigotes and intracellular amastigotes under in vitro stress conditions induced by hydrogen peroxide (H2O2), S-nitroso-N-acetylpenicillamine, or antimonial compounds. Our results demonstrate a stage-specific increase in the levels of protein expression and activity of L. braziliensis CS (LbrCS) and L. braziliensis CβS (LbrCβS), resulting in an increment of total thiol levels in response to both oxidative and nitrosative stress. The rescue of the CS activity in Trypanosoma rangeli, a trypanosome that does not perform cysteine biosynthesis de novo, resulted in increased rates of survival of epimastigotes expressing the LbrCS under stress conditions compared to those of wild-type parasites. We also found that the ability of L. braziliensis promastigotes and amastigotes overexpressing LbrCS and LbrCβS to resist oxidative stress was significantly enhanced compared to that of nontransfected cells, resulting in a phenotype far more resistant to treatment with the pentavalent form of Sb in vitro. In conclusion, the upregulation of protein expression and increment of the levels of LbrCS and LbrCβS activity alter parasite resistance to antimonials and may influence the efficacy of antimony treatment of New World leishmaniasis.

Application of metal–organic frameworks for purification of vegetable oils

Reported here is the synthesis of aluminum-, zinc- and titanium-containing metal–organic frameworks based on terephthalic acid and an investigation on the possibility of using these compounds as adsorbents for the purification of unrefined vegetable oils. It is found that aluminum-, zinc- and titanium-containing metal–organic frameworks improve the physicochemical properties of unrefined vegetable oils (more pleasant taste and odor) due to the binding of free fatty acids and peroxide compounds. It is established that the synthesized materials are more effective in these respects as compared with traditional adsorbents. An adsorption mechanism of free fatty acids and peroxides is proposed. Last but not least, the used MOF can be easily recycled at least five times, via solvent washing.

Effect of biodegradable film (lyophilised alga Fucus spiralis and sorbic acid) on quality properties of refrigerated megrim (Lepidorhombus whiffiagonis)

SummaryThe effect of replacing the on‐board currently employed polyethylene film by a novel type of environmentally friendly packaging was studied. For it, a polylactic acid (PLA) biodegradable film including lyophilised alga Fucus spiralis and sorbic acid was applied during megrim (Lepidorhombus whiffiagonis) refrigeration and its effect on fish quality loss was evaluated. Thus, sensory assessment showed that samples wrapped up with PLA film including 8% alga and 1% sorbic acid were still acceptable on day 11, while control fish specimens (kept under polyethylene film) were rejected at that time. Under such biodegradable film condition, a preservative effect was also implied according to chemical indices assessment related to microbial activity (trimethylamine–N) and lipid oxidation development (peroxide and fluorescent compounds formation); additionally, lower mean numbers for different microbiological groups (aerobes, Enterobacteriaceae and psychrotrophs) were detected. This result provides a promising replacement strategy to enhance refrigerated fish quality and reduce the waste material content.

Evaluating the quality of feed fats and oils and their effects on pig growth performance.

Feed fats and oils provide significant amounts of energy to swine diets, but there is large variation in composition, quality, feeding value, and price among sources. Common measures of lipid quality include moisture, insolubles, and unsaponifiables (MIU), titer, and free fatty acid content, but provide limited information regarding their feeding value. Lipid peroxidation is an important quality factor related to animal growth performance and health, but maximum tolerable limits in various lipids have not been established. Several indicative assays can be used to detect the presence of various peroxidation compounds, but due to the complexity and numerous compounds produced and degraded during peroxidation process, no single method can adequately determine the extent of peroxidation. Until further information is available, using a combination of peroxide value, thiobarbituric acid reactive substances (TBARS), and anisidine value appear to provide a reasonable assessment of the extent of peroxidation in a lipid at a reasonable cost. However, fatty acid composition of the lipid being evaluated should be considered when selecting specific assays. Predictive tests can also be used to estimate the stability or susceptibility of lipids to peroxidation and include active oxygen method, oil stability index, and oxygen bomb method. A review of 16 published studies with pigs has shown an average decrease of 11.4% in growth rate, 8.8% feed intake fed isocaloric diets containing peroxidized lipids compared to diets containing unperoxidized lipids of the same source. Furthermore, serum vitamin E content was generally reduced and serum TBARS content was increased when peroxidized lipids were fed in these studies, suggesting that feeding peroxidized lipids negatively affects metabolic oxidative status of pigs. However, it is unclear if antioxidants are useful additions to lipids to maintain optimal nutritional value, or if their addition to swine diets is beneficial in overcoming a metabolic oxidative challenge.

Modified Polypropylene with Improved Physical-Mechanical Properties

The use of mixtures of benzoyl peroxide and polysiloxane polyol compounds as polypropylene modifiers is suggested. It is established that, in such a way, its physical-mechanical properties can be changed purposefully.

Thermal stability and antioxidant activity of essential oils from aromatic plants farmed in Argentina

Food industries are looking for natural antioxidant to replace synthetic because these last ones are questioned due to healthy reasons. Essential oils are natural products that can have antioxidant activity, but their composition and antioxidant activity could change for thermal storage condition. The objective of this study was to evaluate the antioxidant effect and thermal stability of rosemary, oregano and laurel essential oils (EO). The major components of the essential oils were terpineol (E) Beta (55.5%), terpinen-4-ol (15.9%), and thymol (12.9%) in oregano; camphor (35.7%), verbenone (26.6%), and β-caryophyllene (15.8%) in rosemary EO; and linalool (45.0%), sabinene (31.9%), and methyl eugenol (14.3%) in laurel EO. The volatile composition of the EO changed during the thermal stability study. The antioxidant activity of the essential oils was analyzed measuring free-radical scavenging activity (FRSA) and total phenolic content; and performing a storage study of sunflower oil measuring the formation of peroxide and volatile oxidation compounds. The FRSA showed that laurel (61.74%), oregano (59.97%), and rosemary (48.23%) EOs showed better percentage inhibitions than BHT (8.76%). In the storage study of sunflower oil, samples with 0.10% oregano EO, 0.02% oregano EO, 0.02% laurel EO, and 0.10% rosemary EO showed better antioxidant properties, exhibiting less peroxide and anisidine values during storage. Also, 0.02% oregano EO in the storage study showed reduced formation of volatile compounds like hexanal, 2-heptenal, and 2,4-decadienal. The studied EOs have antioxidant activity and constitute natural potential agents that could be used as antioxidants in food products. Also, the studied EOs are compounds that change under high temperature conditions during storage, which could affect their potential antioxidant activity.

Photocatalytic fluoroalkylation reactions of organic compounds.

Photocatalytic methods for fluoroalkyl-radical generation provide more convenient alternatives to the classical perfluoroalkyl-radical (Rf) production through chemical initiators, such as azo or peroxide compounds or the employment of transition metals through a thermal electron transfer (ET) initiation process. The mild photocatalytic reaction conditions tolerate a variety of functional groups and, thus, are handy to the late-stage modification of bioactive molecules. Transition metal-photocatalytic reactions for Rf radical generation profit from the redox properties of coordinatively saturated Ru or Ir organocomplexes to act as both electron donor and reductive species, thus allowing for the utilization of electron accepting and donating fluoroalkylating agents for Rf radical production. On the other hand, laboratory-available and inexpensive photoorgano catalysts (POC), in the absence of transition metals, can also act as electron exchange species upon excitation, resulting in ET reactions that produce Rf radicals. In this work, a critical account of transition metal and transition metal-free Rf radical production will be described with photoorgano catalysts, studying classical examples and the most recent investigations in the field.

Critical Review: Antioxidant Properties and Antibiotic Mechanism of Honey against Infectious Diseases

The advent of antibiotics in modern western medicine has made the use of honey in the treatment of infectious diseases abandoned. Hence this review exposes why honey remains the best antibiotic and its potency as an antioxidant, antibacterial, and anti-inflammatory. Honey possesses some vital components such as Methylgyloxal, Bee defensin-1, Hydrogen peroxide, osmotic effect and phenolic compounds. Honey also possesses properties that inhibit the formation of biofilms. These made honey more powerful because it prevents the formation of antibiotic-resistant bacteria while conventional antibiotic fail because they only target the essential growth processes of bacteria and this allows bacteria to build up resistance over time.

Role of Lactic Acid Bacteria as Probiotics in Health and Disease

Role of Lactic Acid Bacteria as Probiotics in Health and Disease In natural environment a delicate symbiosis evolves between endogenous bacteria and their host is very crucial for maintaining the internal flora of organisms. It stimulates immune system to respond rapidly to infection with pathogens and through bacterial antagonism it inhibits the colonization of the gut by harmful or pathogenic bacteria. A dominant flora represents 90% of the population, essentially composed of Bifidobactrium and Lactobacilli. In group they are called as Lactic Acid Bacteria (LAB) and are collectively called probiotics. These antibacterial effects of LAB are possible due to different antimicrobial compounds like organic acids, hydrogen peroxide (H2O2), carbon dioxide (CO2), fatty acids, reuterin, bacteriocins and other low molecular mass compounds produced by them. Probiotics is playing an important role in prevention of many bacterial diseases also. Probiotic bacteria may add a low-cost, low risk layer of protection from infection and disease.

ПРИМЕНЕНИЕ ВЫСОКОПОРИСТЫХ НАНОМАТЕРИАЛОВ ДЛЯ ОЧИСТКИ НЕРАФИНИРОВАННЫХ РАСТИТЕЛЬНЫХ МАСЕЛ

Reported here is the preparation of highly porous and stable new nanomaterial based on titanium-containing metal-organic framework compound - TiO2-modified titanium-containing metal-organic framework by magnetron sputtering strategy. The resulting nanomaterial was characterized using XRD, FT-IR, TGA, and AFM techniques. It is shown that TiO2-modified titanium-containing metal-organic framework has awell-ordered structure and consists of homogeneous nanoparticles 50 nm in size. It is established that as-prepared nanomaterial has high thermal stability. The sorption activity of TiO2-modified titanium-containing metal-organic framework for unrefined vegetable oils was studied. It is established that new sorbent improves the physicochemical properties of unrefined vegetable oils due to the binding of free fatty acids and peroxide compounds formed by oil oxidation. TiO2-modified titanium-containing metal-organic framework is more effective adsorbent as compared to non-modified titanium-containing metal-organic framework and traditional industrial and natural adsorbents. It is shown that the used sorbent can be easily recycled at least five times, via solvent washing. An adsorption mechanism of free fatty acids and peroxides is proposed.

Less sensitive oxygen-rich organic peroxides containing geminal hydroperoxy groups.

A series of oxygen-rich organic peroxide compounds each containing two bis(hydroperoxy)methylene groups is described. Energetic testing shows that these compounds are much less sensitive toward impact and friction than existing classes of organic peroxides. The compounds are highly energetic, which may lead to practical peroxide-based explosives.

Rapid degradation of cyclic peroxides by titanium and antimony chlorides.

First responders face extraordinary risks when dealing with organic peroxides such as TATP due to the extreme sensitivity of this class of explosives, and to a lack of a robust chemical means of safe and rapid neutralisation. The Lewis acids TiCl4 and SbCl3 have been found to demonstrate a novel degradation mechanism, with TiCl4 degrading a model cyclic peroxide in minutes when used in a two-fold excess, or ∼3 hours at half equivalence. The products cannot re-form peroxide compounds as is the case with acid degradation, suggesting the two mechanisms are fundamentally different. The Lewis acids mediate a rearrangement reaction in the cyclic peroxide backbone leading to relatively innocuous products through deactivation of oxidising O. Sub-stoichiometric TiCl4 reactions highlight a secondary reaction pathway that also leads to some oxidative chlorination products, possibly mediated by an unconfirmed titanium-oxychloride species. SbCl3 was found to exhibit similar reactivity to TiCl4, although at a slower rate. A mechanism is proposed, consistent with the observations for both stoichiometric and sub-stoichiometric quantities of TiCl4.

Effects of postharvest oligochitosan treatment on anthracnose disease in citrus (Citrus sinensis L. Osbeck) fruit

Citrus fruit (Citrus sinensis L. Osbeck) is susceptible to infection by Colletotrichum gloeosporioides during poststorage, which rapidly decreases sensory and nutritional quality of the fruit. The ability of oligochitosan treatment to control C. gloeosporioides of citrus fruit during storage was examined, and possible underlying mechanisms were discussed. Disease incidence and lesion diameter were lower in oligochitosan-treated fruits compared with their respective controls. The fruits dipped in oligochitosan showed increased contents of lignin, hydroxyproline-rich glycoprotein (HRGP), hydrogen peroxide (H2O2), ascorbate, glutathione, total phenol, and flavonoid compounds. In addition, enzymatic activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7), polyphenoloxidase (PPO, EC 1.14.18.1), ascorbate peroxidase (APX, EC 1.11.1.11), and β-1, 3-glucanase (GLU, EC 3.2.1.39) also increased in citrus fruit peels, all of which were correlated with the onset of induced disease resistance. These results indicated that oligochitosan treatment can induce disease resistance of citrus fruit to C. gloeosporioides Penz. Oligochitosan can be a potential alternative to conventional control methods of postharvest anthracnose in citrus fruit.

Процессы перекисного окисления липидов и показатели функции антиоксидантной системы организма при СВЧ-воздействии различной интенсивности (обзор)

Identification of patterns and the search mechanism of interaction products of lipid peroxidation with antioxidant system in the body, as well as selection methods offset correction of biochemical parameters is an important issue of preventive and clinical medicine. The universal response of any organism to the action of one or a group of harmful factors is the increase of energy production in the cells of adaptive systems. It is known that depleted stocks of vitamins antioxidant and peroxide compounds begin to damage the membrane and the receptor apparatus of the functioning and dividing cells. In recent years there have been publications which provide information about a variety of shifts in the LP processes and the function of the antioxidant system of the organism during microwave exposure. Shifts in the processes of lipid peroxidation and the function of the antioxidant system of the organism are present when exposed to EMFs of different frequency bands, but this information doesn’t systematized, contradictory and doesn’t disclosed the full information on the mechanism of action of this factor on the body. This literature review is devoted to the analysis of Russian publications in recent years, about changes of peroxidation processes and the function of the antioxidant system of the organism in the microwave effect of different intensity.

Expanding the crystal chemistry of uranyl peroxides: four hybrid uranyl-peroxide structures containing EDTA.

The first four uranyl peroxide compounds containing ethylenediaminetetra-acetate (EDTA) were synthesized and characterized from aqueous uranyl peroxide nitrate solutions with a pH range of 5-7. Raman spectra demonstrated that reaction solutions that crystallized [NaK15[(UO2)8(O2)8(C10H12O10N2)2(C2O4)4]·(H2O)14] (1) and [Li4K6[(UO2)8(O2)6(C10H12O10N2)2(NO3)6]·(H2O)26] (2) contained excess peroxide, and their structures contained oxidized ethylenediaminetetraacetate, EDTAO2(4-). The solutions from which [K4[(UO2)4(O2)2(C10H13O8N2)2(IO3)2]·(H2O)16] (3) and LiK3[(UO2)4(O2)2(C10H12O8N2)2(H2O)2]·(H2O)18 (4) crystallized contained no free peroxide, and the structures incorporated intact EDTA(4-). In contrast to the large family of uranyl peroxide cage clusters, coordination of uranyl peroxide units in 1-4 by EDTA(4-) or EDTAO2(4-) results in isolated tetramers or dimers of uranyl ions that are bridged by bidentate peroxide groups. Two tetramers are bridged by EDTAO2(4-) to form octamers in 1 and 2, and dimers of uranyl polyhedra are linked through iodate groups in 3 and EDTA(4-) in 4, forming chains in both cases. In each structure the U-O2-U dihedral angle is strongly bent, at ∼140°, consistent with the configuration of this linkage in cage clusters and other recently reported uranyl peroxides.

Оxidation of isomeric hydroxytoluenes with ozone in acetic anhydride

The reaction of ozone with isomeric hydroxytoluenes in acetic anhydride medium to obtain corresponding aromatic alcohols and aldehydes was investigated. It was shown that in the research conditions, acetic anhydride acts as both solvent and acylating agent. The main reaction products are aliphatic peroxides (80-90%), corresponding acetoxybenzylacetates (7-14%) and acetoxybenzaldiacetates (3-6%) were identified among the oxidation products by the methyl group of substrates. A scheme for the liquid-phase oxidation of acetoxytoluenes with ozone in acetic anhydride, which explains the obtained experimental data was proposed. During the studies, the concentration of methylbenzenes and their conversion products in the solution was determined by gas-liquid chromatography at chromatograph with a flame ionization detector. The content of peroxide compounds was determined by iodometric titration. The rate constants of the reaction of ozone with methylbenzenes were calculated using the method, described in the work [3]. The obtained experimental data are the basis for developing environmentally friendly methods of synthesis of hydroxybenzyl alcohols and hydroxybenzaldehydes.

Role of tunable acid catalysis in decomposition of α-hydroxyalkyl hydroperoxides and mechanistic implications for tropospheric chemistry.

Electronic structure calculations have been used to investigate possible gas-phase decomposition pathways of α-hydroxyalkyl hydroperoxides (HHPs), an important source of tropospheric hydrogen peroxide and carbonyl compounds. The uncatalyzed as well as water- and acid-catalyzed decomposition of multiple HHPs have been examined at the M06-2X/aug-cc-pVTZ level of theory. The calculations indicate that, compared to an uncatalyzed or water-catalyzed reaction, the free-energy barrier of an acid-catalyzed decomposition leading to an aldehyde or ketone and hydrogen peroxide is dramatically lowered. The calculations also find a direct correlation between the catalytic effect of an acid and the distance separating its hydrogen acceptor and donor sites. Interestingly, the catalytic effect of an acid on the HHP decomposition resulting in the formation of carboxylic acid and water is relatively much smaller. Moreover, since the free-energy barrier of the acid-catalyzed aldehyde- or ketone-forming decomposition is ∼ 25% lower than that required to break the O-OH linkage of the HHP leading to the formation of hydroxyl radical, these results suggest that HHP decomposition is likely not an important source of tropospheric hydroxyl radical. Finally, transition state theory estimates indicate that the effective rate constants for the acid-catalyzed aldehyde- or ketone-forming HHP decomposition pathways are 2-3 orders of magnitude faster than those for the water-catalyzed reaction, indicating that an acid-catalyzed HHP decomposition is kinetically favored as well.

ПРИМЕНЕНИЕ МЕТАЛЛООРГАНИЧЕСКИХ КАРКАСНЫХ СОЕДИНЕНИЙ ДЛЯ ОЧИСТКИ РАФИНИРОВАННЫХ РАСТИТЕЛЬНЫХ МАСЕЛ

Titanium-containing metal-organic framework synthesis based on terephthalic acid is presented. The resulting compound was characterized using physicochemical methods: BET, XRD, IR spectroscopy. The possibility of using of this compound as a sorbent for refined vegetable oils purification was studied. It is established that titanium-containing metal-organic framework improves the physical and chemical properties of refined vegetable oils owing to coupling of free fatty acids and peroxide compounds formed by oxidation.

The Adsorption of Undesirable Impurities from Sunflower Oil on the Granulated Sorbents Based on Kaolin Clay

Abstract Modifying processes of clay of Veselovskoe deposits with acetic acid (AA) and liquid sodium glass and adsorption of undesirable impurities from sunflower oil on granulated sorbent in a dynamic mode were studied. It was shown that the modification of clay with AA increases the number of Brönsted sites and yields granulated sorbent with a mesopore structure. The composition of clay and liquid glass is characterized by the basic sites. The composition of the clay modified with AA and the liquid glass produces all kinds of surface sites and yields the bipore structure. It was established that the modification of clay with liquid glass provides highest degree of adsorption of the fatty acid (84.6–87.7%), and the modification of clay with AA leads to increasing adsorption of the peroxide compounds (70.0–81.7%). Both acid and alkaline modification of clay allows increasing the phosphorated substances extraction degree to 77.2–89.4%.