Catechol Autoxidation Research Articles

Utilizing Rapid Hydrogen Peroxide Generation from 6-Hydroxycatechol to Design Moisture-Activated, Self-Disinfecting Coating.

A coating that can be activated by moisture found in respiratory droplets could be a convenient and effective way to control the spread of airborne pathogens and reduce fomite transmission. Here, the ability of a novel 6-hydroxycatechol-containing polymer to function as a self-disinfecting coating on the surface of polypropylene (PP) fabric was explored. Catechol is the main adhesive molecule found in mussel adhesive proteins. Molecular oxygen found in an aqueous solution can oxidize catechol and generate a known disinfectant, hydrogen peroxide (H2O2), as a byproduct. However, given the limited amount of moisture found in respiratory droplets, there is a need to enhance the rate of catechol autoxidation to generate antipathogenic levels of H2O2. 6-Hydroxycatechol contains an electron donating hydroxyl group on the 6-position of the benzene ring, which makes catechol more susceptible to autoxidation. 6-Hydroxycatechol-coated PP generated over 3000 μM of H2O2 within 1 h when hydrated with a small amount of aqueous solution (100 μL of PBS). The generated H2O2 was three orders of magnitude higher when compared to the amount generated by unmodified catechol. 6-Hydroxycatechol-containing coating demonstrated a more effective antimicrobial effect against both Gram-positive (Staphylococcus aureus and Staphylococcus epidermidis) and Gram-negative (Pseudomonas aeruginosa and Escherichia coli) bacteria when compared to unmodified catechol. Similarly, the self-disinfecting coating reduced the infectivity of both bovine viral diarrhea virus and human coronavirus 229E by as much as a 2.5 log reduction value (a 99.7% reduction in viral load). Coatings containing unmodified catechol did not generate sufficient H2O2 to demonstrate significant virucidal effects. 6-Hydroxycatechol-containing coating can potentially function as a self-disinfecting coating that can be activated by the moisture present in respiratory droplets to generate H2O2 for disinfecting a broad range of pathogens.

Proof of Aerobically Autoxidized Self-Charge Concept Based on Single Catechol-Enriched Carbon Cathode Material

HighlightsAn air-breathing chemical self-charge concept of oxygen-enriched carbon cathode.The oxygen-enriched carbon material with abundant catechol groups.Rapid air-oxidation chemical self-charge of catechol groups.The self-charging concept has drawn considerable attention due to its excellent ability to achieve environmental energy harvesting, conversion and storage without an external power supply. However, most self-charging designs assembled by multiple energy harvesting, conversion and storage materials increase the energy transfer loss; the environmental energy supply is generally limited by climate and meteorological conditions, hindering the potential application of these self-powered devices to be available at all times. Based on aerobic autoxidation of catechol, which is similar to the electrochemical oxidation of the catechol groups on the carbon materials under an electrical charge, we proposed an air-breathing chemical self-charge concept based on the aerobic autoxidation of catechol groups on oxygen-enriched carbon materials to ortho-quinone groups. Energy harvesting, conversion and storage functions could be integrated on a single carbon material to avoid the energy transfer loss among the different materials. Moreover, the assembled Cu/oxygen-enriched carbon battery confirmed the feasibility of the air-oxidation self-charging/electrical discharging mechanism for potential applications. This air-breathing chemical self-charge concept could facilitate the exploration of high-efficiency sustainable air self-charging devices.

Astrocyte Reaction to Catechol-Induced Cytotoxicity Relies on the Contact with Microglia Before Isolation.

Astrocytes preserve the brain microenvironment homeostasis in order to protect other brain cells, mainly neurons, against damages. Glial cells have specific functions that are important in the context of neuronal survival in different models of central nervous system (CNS) diseases. Microglia are among these cells, secreting several molecules that can modulate astrocyte functions. Although 1,2-dihydroxybenzene (catechol) is a neurotoxic monoaromatic compound of exogenous origin, several endogenous molecules also present the catechol group. This study compared two methods to obtain astrocyte-enriched cultures from newborn Wistar rats of both sexes. In the first technique (P1), microglial cells began to be removed early 48h after primary mixed glial cultures were plated. In the second one (P2), microglial cells were late removed 7 to 10days after plating. Both cultures were exposed to catechol for 72h. Catechol was more cytotoxic to P1 cultures than to P2, decreasing cellularity and changing the cell morphology. Microglial-conditioned medium (MCM) protected P1 cultures and inhibited the catechol autoxidation. P2 cultures, as well as P1 in the presence of 20% MCM, presented long, dense, and fibrillary processes positive for glial fibrillary acidic protein, which retracted the cytoplasm when exposed to catechol. The Ngf and Il1beta transcription increased in P1, meanwhile astrocytes expressed more Il10 in P2. Catechol decreased Bdnf and Il10 in P2 cultures, and it decreased the expression of Il1beta in both conditions. A prolonged contact with microglia before isolation of astrocyte-enriched cultures modifies astrocyte functions and morphology, protecting these cells against catechol-induced cytotoxicity.

Products of Prolonged Autoxidation of Simple Dihydric Phenols in the Presence of Copper(II) Ions – An Electron Spin Resonance Study

Electron spin resonance (ESR) spectroscopy was used for characterizing the products obtained by prolonged autoxidation of simple dihydric phenols (hydroquinone, catechol, and 4-methylcatechol) in the presence of copper(II) ions. Room temperature ESR spectra revealed that both paramagnetic copper(II) ions and organic radicals are present in obtained autoxidation products similarly to the humic acid complexed copper(II) ions. The ratio of organic radical signal intensity to the copper(II) ion signal intensity suggests that the smallest amount of copper(II) ions is incorporated in the hydroquinone autoxidation product while the highest amount of copper(II) ions is incorporated in the autoxidation product of catechol. Satisfactory computer simulations of experimental ESR spectra were obtained by considering only one type of copper(II) ion binding site for hydroquinone autoxidation product and two distinct types of copper(II) ion binding sites for catechol and 4-methylcatechol autoxidation products. Parameters obtained by the computer simulation of ESR spectra indicated prevalent ionic bonding of copper(II) ions in polymeric matrices with tetrahedral distortion at copper(II) ion binding sites and negligible exchange interactions between them. Products obtained by the hydroquinone and catechol autoxidation have more similar characteristics in comparison to the product obtained by the 4-methylcatechol autoxidation where more expressed ionic bonding of copper(II) ions, and smaller tetrahedral distortion are present. Due to the dipolar interactions of oxygen-centered organic radicals in autoxidation products with paramagnetic copper(II) ions, their ESR linewidths are larger and g-values smaller in comparison to the values found in humic acids from various soil types.

The Study of Mg(II) Ion Influence on Catechol Autoxidation in Weakly Alkaline Aqueous Solution

High performance liquid chromatography with diode array detection (HPLC-DAD) and electron spin resonance (ESR) spectroscopy were used to study Mg(II) ion influence on the autoxidation of catechol in weakly alkaline solution. The presence of Mg(II) ions greatly enhanced the catechol autoxidation rate and probably influenced the mechanism of reaction thus enabling formation of reaction products not obtained in the absence of metal ions. Consecutive formation of 1,2-benzoquinone, 2,3-oxanthrenediol, and 2,3-oxanthrenedione with intermediate o-semiquinone anion radicals during the initial stages of catechol autoxidation was suggested based on the detailed analysis of experimental HPLC-DAD and ESR data. The results of this study may help in better understanding of autoxidation of some biologically important catecholic molecules in real systems, where Mg(II) ions are ubiquitously present. Because of the possible toxicity of simple quinone molecules, it is important that the formation of relatively stable quinoid autoxidation products were detected in this study.

Biomimetic recyclable microgels for on-demand generation of hydrogen peroxide and antipathogenic application

Microgels that can generate antipathogenic levels of hydrogen peroxide (H2O2) through simple rehydration in solutions with physiological pH are described herein. H2O2 is a widely used disinfectant but the oxidant is hazardous to store and transport. Catechol, an adhesive moiety found in mussel adhesive proteins, was incorporated into microgels, which generated 1–5 mM of H2O2 for up to four days as catechol autoxidized. The sustained release of low concentrations of H2O2 was antimicrobial against both gram-positive (Staphylococcus epidermidis) and gram-negative (Escherichia coli) bacteria and antiviral against both non-enveloped porcine parvovirus (PPV) and enveloped bovine viral diarrhea virus (BVDV). The amount of released H2O2 is several orders of magnitude lower than H2O2 concentration previously reported for antipathogenic activity. Most notably, these microgels reduced the infectivity of the more biocide resistant non-envelope virus by 3 log reduction value (99.9% reduction in infectivity). By controlling the oxidation state of catechol, microgels can be repeatedly activated and deactivated for H2O2 generation. These microgels do not contain a reservoir for storing the reactive H2O2 and can potentially function as a lightweight and portable dried powder source for the disinfectant for a wide range of applications. Statement of SignificanceResearchers have designed bioadhesives and coatings using the adhesive moiety catechol to mimic the strong adhesion capability of mussel adhesive proteins. During catechol autoxidation, hydrogen peroxide (H2O2) is generated as a byproduct. Here, catechol was incorporated into microgels, which can generate millimolar levels of H2O2 by simply hydrating the microgels in a solution with physiological pH. The sustained release of H2O2 was both antimicrobial and antiviral, inactivating even the more biocide resistant non-enveloped virus. These microgels can be repeatedly activated and deactivated for H2O2 generation by incubating them in solutions with different pH. This simplicity and recyclability will enable this biomaterial to function as a lightweight and portable source for the disinfectant for a wide range of applications.

Effect of Ionic Functional Groups on the Oxidation State and Interfacial Binding Property of Catechol-Based Adhesive.

Adhesive hydrogels were prepared by copolymerizing dopamine methacrylamide with either acrylic acid (AAc) or N-(3-aminopropyl)methacrylamide hydrochloride (APMH). The effect of incorporating the anionic and cationic side chains on the oxidation state of catechol was characterized using the FOX assay to track the production of hydrogen peroxide byproduct generated during the autoxidation of catechol, and the interfacial binding property of the adhesive was determined by performing Johnson-Kendall-Roberts contact mechanics tests tested over a wide range of pH values (pH 3.0-9.0). The ionic species contributed to interfacial binding to surfaces with the opposite charge with measured work of adhesion values that were comparable to or in some cases higher than those of catechol. Addition of AAc minimized the oxidation of catechol even at a pH of 8.5 and correspondingly preserved the elevated adhesive property of catechol to both quartz and amine-functionalized surfaces. However, AAc lost its buffering capacity at pH 9.0, and catechol was oxidized at this pH. On the other hand, catechol formed a cohesive covalent bond with the network-bound amine side chain of APMH at basic pH, which interfered with the interfacial binding capability of APMH and the catechol.

Combined Activation of Methyl Paraben by Light Irradiation and Esterase Metabolism toward Oxidative DNA Damage

Methyl paraben (MP) is often used as a preservative in foods, drugs, and cosmetics because of its high reliability in safety based on the rapid excretion and nonaccumulation following administration. Light irradiation sometimes produces unexpected activity from chemicals such as MP; furthermore, there is ample opportunity for MP to be exposed to sunlight. Here, we investigated whether MP shows DNA damage after sunlight irradiation. Two major photoproducts, p-hydroxybenzoic acid (PHBA) and 3-hydroxy methyl paraben (MP-3OH), were detected after sunlight irradiation to an aqueous MP solution. Both photoproducts were inactive in the in vitro DNA damage assay that measures oxidized guanine formed in calf thymus DNA in the presence of divalent copper ion, a known mediator of oxidative DNA damage. Simulated MP metabolism using dermal tissues after light irradiation produced these two photoproducts, which reacted with a microsomal fraction (S9) of the skin. A metabolite from MP-3OH, not PHBA, caused distinct DNA damage in the in vitro assay. This active metabolite was identified as protocatechuic acid, a hydrolyzed MP-3OH product. In addition, NADH, a cellular reductant, enhanced DNA damage by approximately five times. These results suggest that reactive oxygen species generated by the redox cycle via metal ion and catechol autoxidation are participating in oxidative DNA damage. This study reveals that MP might cause skin damage involving carcinogenesis through the combined activation of sunlight irradiation and skin esterases.

Mechanism of Interaction of Polyphenols, Oxygen, and Sulfur Dioxide in Model Wine and Wine

The interaction of oxygen, sulfur dioxide, and 4-methylcatechol (4-MeC) was studied in a model wine containing catalytic concentrations of iron and copper in order to provide further evidence that when a catechol and oxygen interact, hydrogen peroxide and a quinone are formed, both of which react with SO₂. The aerial oxidation of the catechol in the presence of benzenesulfinic acid (BSA) slowly produced the BSA-quinone adduct in high yield. It was also quickly prepared by adding ferric chloride, demonstrating that the quinone is cleanly produced in this model wine and that the catechol is rapidly oxidized by Fe(III) ions. This reaction is important in the catalytic function of the metal. The oxygen and SO₂ molar reaction ratio was 1:2, which is consistent with one mole equivalent of SO₂ reacting with hydrogen peroxide and a second with the quinone. When BSA was added to the system to trap the quinone the ratio was reduced to 1:1. The rate of reaction of oxygen and SO₂ increased with catechol concentration. However, the rate of reaction of oxygen was also markedly accelerated by SO₂ and by BSA, and it is proposed that substances that react with quinones accelerate catechol autoxidation. When 4-MeC was oxidized in the presence of SO₂, ~38% of the quinone that was formed reacted with bisulfite to produce the sulfonic acid adduct and most of the remainder was reduced back to the catechol. The O₂/SO₂ molar reaction ratio in two red wines was 1:~1.7, suggesting that some nucleophilic substances may be competing with bisulfite for quinones. The rate of reaction of oxygen was also accelerated by SO₂ in red wine.

Abiotic transformation of catechol and 1-naphthol in aqueous solution—Influence of environmental factors

The abiotic transformation of catechol and 1-naphthol singly and in mixtures was tested in sterile Tris-HCl buffer with regard to several environmental factors including temperature (7°C, 20°C and 30°C), lighting conditions, pH (between 7.0 and 8.5) and dissolved oxygen (at partial pressures of 0.0, 220, 2200, 11000 and 22000 Pa). Irrespective of lighting conditions, catechol autoxidation was confirmed in aerated medium with a rate independent of the presence of 1-naphthol but proportional to the dissolved oxygen concentration, to the pH (its half-disappearance occurred in 24 h at pH 8.5) and, to a lesser extent, to the incubating temperature (at 20°C, 20% disappeared in 10 days at pH 7.0). Under alkaline conditions, the reaction of the anionic form (catecholate) with an equimolar concentration of molecular oxygen (O 2) led presumably to hydrogen peroxide anion (HO 2 −) and coloured polymerization products. When tested alone, 1-naphthol was not significantly influenced either by lighting conditions, incubating temperature or dissolved oxygen concentration. It was also found to be quite stable with respect to pH, with a 15-fold weaker transformation rate than for catechol at the highest pH used. When tested in a mixture with catechol, 1-naphthol was found to be involved in a new chemical oxidation reaction catalyzed by catecholate. The transformation of one mole of 1-naphthol consumes four moles of oxygen. In the presence of catechol, the stoichiometry of the 1-naphthol transformation, under the influence of oxygen, suggests the possible formation of 2,5,6,8-tetrahydroxy 1,4-naphthoquinone via Lawsone (2-hydroxy 1,4-naphthoquinone) and naphthopurpurine (2,5,8-trihydroxy 1,4-naphthoquinone) as hypothetic intermediates. This is the first report of the autoxidation of 1-naphthol, catalyzed by catechol, in aqueous solution, in the absence of UV irradiation.

COMT-dependent protection of dopaminergic neurons by methionine, dimethionine and S-adenosylmethionine (SAM) against l-dopa toxicity in vitro

l-dopa may be toxic to dopamine neurons, possibly due to catechol-autoxidation. Catechols are O-methylated by catechol- O-methyltransferase (COMT) in a SAM consuming reaction, preventing the initiation of catechol autoxidation. We hypothesized that SAM or SAM-precursors ameliorate l-dopa neurotoxicity, in a COMT-dependent fashion. We tested this hypothesis in primary mesencephalic cultures by adding 200 μM l-dopa with 2 mM methionine or 1 mM dimethionine or 0.5 mM SAM with or without 0.2 μM of the COMT-inhibitor 2′, 5′-dinitrocatechol (OR 486). l-dopa was found to be neurotoxic as the surviving neurons had fewer and shorter processes. Methionine, dimethionine and SAM all protected DA neurons against damaged induced by l-dopa. The COMT inhibitor dinitrocatechol (DNC) completely abolished the protective effect against l-dopa toxicity. We conclude that supplementation with methionine, dimethionine or SAM ameliorates l-dopa neurotoxicity to dopamine neurons, while inhibition of COMT may aggravate or unmask l-dopa neurotoxicity.

Chemical Simulation of Biogenesis of the 2,4,5-Trihydroxyphenylalanine Quinone Cofactor of Copper Amine Oxidases: Mechanistic Distinctions Point toward a Unique Role of the Active Site in the o-Quinone Water Addition Step

The biogenesis of the 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor from tyrosine at the active site of copper amine oxidases is believed to proceed along a pathway that includes a conjugate addition of water to the corresponding o-quinone intermediate, followed by autoxidation of the resulting benzenetriol to the hydroxyquinone cofactor. The water addition reaction has been presumed to occur not only in previous model studies reported for cofactor biogenesis starting with either catechol or o-quinone, but also for generation of the neurotoxin 6-hydroxydopamine during autoxidation of dopamine. We here report the surprising finding that water addition does not occur under solution chemistry conditions. The production of hydroxyquinone from catechol arises instead from reaction of the o-quinone with H2O2 generated during autoxidation of catechol. When starting with the o-quinone itself, production of hydroxyquinone still arises from autoxidation of the catechol, generated either by reduction of the o...

Effects of inhibition of monoamine oxidase on the levels of 5-S-cysteinyl adducts of catechols in dopaminergic regions of the brain of the guinea pig

The occurrence of 5-S-cysteinyl adducts of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylalanine (DOPA) in brain tissue, appears to reflect in vivo autoxidation of DA, DOPA and DOPAC, respectively. In the striatum and in the limbic system of guinea pig, the levels of DOPAC and 5-S-cysteinyl-DOPAC were markedly reduced after treatment with pargyline (75 mg/kg, i.p., 17 hr) and pargyline plus reserpine (75 mg/kg, i.p., 17 hr plus 5 mg/kg, i.p., 18 hr) compared to controls. However, the depletion of 5-S-cysteinyl adduct was less severe than that of DOPAC, suggesting a slower turnover of the adduct. Dopamine and 5-S-cysteinyl-DA increased significantly and to the same extent in the striatum, after pargyline alone. In the limbic system DA was significantly increased, whereas no change was found for levels of 5-S-cysteinyl-DA. 5-S-Cysteinyl-DOPA decreased significantly in the striatum after treatment with pargyline plus reserpine and non-significantly after pargyline alone. The data are compatible with a slight inhibitory effect of MAO inhibition on catechol autoxidation. This effect was, however, overridden by the increased level of DA.

Oxidative Breakdown Products of Catecholamines and Hydrogen Peroxide Induce Partial Metamorphosis in the Nudibranch Phestilla sibogae Bergh (Gastropoda: Opisthobranchia).

Veliger larvae of the aeolid nudibranch Phestilla sibogae metamorphose in response to a soluble factor from their prey coral, Porites compressa. Metamorphosis begins with destruction of the velum, a ciliated structure used for swimming and feeding. Previous investigation had shown that P. sibogae larvae exposed to certain catecholamines lost the velum, but then failed to complete any subsequent steps characteristic of natural coral-induced metamorphosis. Because catecholamines oxidize rapidly in seawater, we have re-examined morphogenic effects of catecholamines using superfusion chambers that allow periodic replacement of test solutions. We report that fresh, unoxidized catecholamines do not induce velar loss, but that this morphogenic activity develops in aged, oxidized solutions of a variety of catecholamines and other catechol compounds. Evidence is presented that this activity is attributable to hydrogen peroxide, a byproduct of catechol autoxidation. Hydrogen peroxide induces velar loss at 10-4 M. The possible relationship of peroxide-induced velar loss to natural coral-induced metamorphosis is discussed.

Vitamin C Deficiency Facilitates 5‐S‐Cysteinyldopamine Formation in Guinea Pig Striatum

Being a catechol, dopamine (DA) is easily autoxidized in solution to a semiquinone and then further to a quinone. These quinones and by-products, as reduced forms of oxygen, are all cytotoxic. By quantifying quinone metabolites, such as 5-S-cysteinyl adducts of DA, 3,4-dihydroxyphenylalanine (DOPA), and 3,4-dihydroxyphenylacetic acid (DOPAC), an indirect measure of catechol autoxidation is available. Ascorbic acid (AA) has an important role as an antioxidant in the organism. A group of guinea pigs (Dunkin-Hartley) received an AA-free diet for 37 days, whereas a control group was fed an AA-containing diet (1,400 mg/kg of pellets). To one group of AA-deprived animals a single dose of AA (500 mg/kg, i.p.) was administered 2 h before death, whereas another group received two doses 9 and 24 h before death. The striatal levels of 5-S-cysteinyl adducts, DA, noradrenaline, and DOPAC and the cerebellar and the limbic levels of AA were determined. A significant increase in 5-S-cysteinyl-DA content was found in the striatum of AA-deficient animals (143 +/- 12% of control values). A further increase was found 2 h after an AA injection (177 +/- 16% of control values), which was significant compared with both controls and AA-deficient animals. An elevation in 5-S-cysteinyl-DA content was still observed following two AA injections during a 24-h period (153 +/- 7% of control values). The 5-S-cysteinyl-DOPAC content increased significantly (134 +/- 14% of control values) in the AA-deficient animals given AA acutely (2 h), both compared with controls and with the AA-deficient group.(ABSTRACT TRUNCATED AT 250 WORDS)

An Improved HPLC‐Electrochemical Detection Method for Measuring Brain Levels of 5‐S‐Cysteinyldopamine, 5‐S‐Cysteinyl‐3,4‐Dihydroxyphenylalanine, and 5‐S‐Cysteinyl‐3,4‐Dihydroxyphenylacetic Acid

Brain levels of the 5-S-cysteinyl adducts of 3,4-dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylacetic acid (DOPAC), and dopamine were determined in several mammalian species. The low levels of the compounds and the risk of artifacts during sample preparation necessitated rather profound modifications of the assaying method. The refined method has made it possible to present more accurate data than those previously reported from this laboratory. The occurrence of low levels of the 5-S-cysteinyl adducts in dopamine-rich brain areas, but not in cerebellum, is indirect evidence of in vivo autoxidation of DOPA, DOPAC, and dopamine. The products generated during catechol autoxidation, including quinones and reduced forms of oxygen, are known to be potentially cytotoxic.

Interactions of manganese with human brain glutathione- S-transferase

Chronic exposure to manganese-laden dusts induces, in humans and lower primates, neurological disorders with clinicopathological features that resemble idiopathic Parkinson's disease. As many authors have suggested, manganese neurotoxicity could be related to the capability of this metal to increase catechol autoxidation in catecholaminergic neurons, therefore increasing the formation of toxic compounds such as peroxides, superoxides, free radicals, and semi-orthoquinones. Oxidative stresses and consequent neuronal damage could then occur if physiological scavenger mechanisms fail in their detoxifying action. We here report that manganese chloride weakly inhibits, in a dose-dependent way by a reversible competitive mechanism, human brain glutathione- S-transferases possibly suggesting that manganese intoxication could cause intraneuronal accumulation of cytotoxic compounds. We also report that both 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, a neurotoxin known to induce in man Parkinson-like syndromes, and one of its metabolites 1-methyl-4-phenylpyridinium failed to decrease glutathione- S-transferase activity.

Oxygen activation. II. The effect of catecholamines

1. Adrenal hormones greatly accelerated the autoxidation of p-hydroquinone by activating the O 2 molecule through complex formation by charge transfer. 2. O 2 activation by o-diphenolic compounds was also observed by using p-phenylenediamine as substrate. This explains the abnormally high O 2 uptake by the diamine in the presence of melanoma extracts, DOPA or catechol (the Greenstein-Riley effect). 3. The kinetics of catechol autoxidation is consistent with the view that one molecule is oxidized while a second catechol molecule acts as activator. 4. It is suggested that one of the primary roles of catecholamines is to active O 2.