Catechol Compounds Research Articles

Fe(III)/Polydopamine-Mediated Capture and Release of Catecholic Compounds

Ali et al. performed variouschemical analyses including BAC, and found that the squidbeak consists of chitin, water, and DOPA-containing pro-teins. Although the exact role of DOPA-containing proteinshas not been elucidated, the identification of the specificprotein provided a meaningful insight to understand theextraordinary mechanical properties of squid beak. BAC hasbeen also utilized in the analysis of sandcastle worm’sunderwater adhesion.

Detoxifying polyhalogenated catechols through a copper-chelating agent by forming stable and redox-inactive hydrogen-bonded complexes with an unusual perpendicular structure.

The use of selective metal chelating agents with preference for binding of a specific metal ion to investigate its biological role is becoming increasingly common. We found recently that a well-known copper-specific chelator 2,9-dimethyl-1,10-phenanthroline (2,9-Me2OP) could completely inhibit the synergistic toxicity induced by tetrachlorocatechol (TCC) and sodium azide (NaN3). However, its underlying molecular mechanism is still not clear. Here, we show that the protection by 2,9-Me2OP is not due to its classic copper-chelating property, but rather due to formation of a multiple hydrogen-bonded complex between 2,9-Me2OP and TCC, featuring an unusual perpendicular arrangement of the two binding partners. The two methyl groups at the 2,9 positions in 2,9-Me2OP were found to be critical to stabilize the 2,9-Me2OP/TCC complex due to steric hindrance, and therefore completely prevents the generation of the reactive and toxic semiquinone radicals by TCC/NaN3. This represents the first report showing that an unexpected new protective mode of action for the copper "specific" chelating agent 2,9-Me2OP by using its steric hindrance effect of the two CH3 groups not only to chelate copper, but also to "chelate" a catechol through multiple H-bonding. These findings may have broad biological implications for future research of this widely used copper-chelating agent and the ubiquitous catecholic compounds.

Comparison of biological and chemical treatment processes as cost-effective methods for elimination of benzoate in saline wastewaters

Eight mixed cultures able to degrade benzoic acid under saline conditions were established and kinetic parameters were determined in batch processes with cultures SBM002 (0.5 g d−1·g oDM−1), SBM003 (0.7 g d−1·g oDM−1) and SBM007 (2.2 g d−1·g oDM−1) showing the highest degradation rates. Treatability of an industrial waste water (12 g L−1 benzoic acid, 82 g L−1 NaCl) by these cultures was proven in a fed-batch system (SBM002 & SBM003) and a continuous flow reactor (SBM007). The performance of the continuous flow reactor was 15-times higher compared to the fed-batch system due to the change of inocula, higher concentration of ammonia as nutrient and less accumulation of possibly toxic catecholic compounds. Average DOC reduction was found to be 98% at 100 g L−1 NaCl and 1.2 g L−1 benzoic acid under these conditions. Pre-treatment of the waste water via chemical precipitation by acidification to pH 3.5 diminished the concentration of benzoic acid to 2.1 g L−1. In a combined chemical-biological process the volume of the bioreactor is reduced to 15% compared to a pure biological process. A comparison of operational costs for these three alternatives is presented.

Improved hydrodynamic permeability and antifouling properties of poly(vinylidene fluoride) membranes using polydopamine nanoparticles as additives

This study aims to improve the hydrodynamic permeability and antifouling properties of poly(vinylidene fluoride) (PVDF) membranes using bioinspired polydopamine nanoparticles (PDA NPs) as additives during membranes formation. Based on the oxidant-induced polymerization behavior of dopamine, a series of PDA NPs were first prepared in different reaction mediums. Subsequently, the synthesized PDA NPs were used as additives to produce PVDF/PDA blend membranes. Data of water contact angle measurements show that the hydrophilicity of the blend membranes is improved obviously compared with that of the unmodified PVDF membrane. The water permeability and antifouling properties of the PVDF membranes are both enhanced after blending modification as evaluated by protein filtration tests. Results from tensile test indicate that an appropriate amount of PDA NPs is able to improve the toughness of the as-prepared blend membranes. Moreover, the PVDF/PDA blend membranes have satisfying long-term stability in aqueous environment. This strategy can be extended to more polymers and catechol compounds, and allows exploitation of novel functional composites from bioinspired catecholic chemistry and simple blending process.

EPA-0138 – Comt val158met polymorphism interacts with sex to influence fear conditioning and extinction in healthy humans

The acquisition and extinction of conditioned fear underlies the pathophysiology of anxiety disorders, including PTSD. Women have higher lifetime prevalence and greater risk of PTSD than men. Such sex differences may be attributed to a combination of genetic and hormonal factors. The catechol-O-methyltransferase (COMT) gene encodes an enzyme that metabolizes catechol compounds, including dopamine. The COMT Val158Met polymorphism affects the enzymatic activity of dopamine and has been associated with altered fear memory performance. Besides, when estrogen secretion is elevated, women show a greater extinction of conditioned fear than men. Here, we investigated the relationship between the COMT genotype and sex in the acquisition and extinction of conditioned fear. In a 3-day cued fear conditioning experiment, acquisition and extinction performance of 75 healthy men (21.8 years) and 45 healthy women in follicular phase (21.2 years) were examined. Visual cues and electric shocks were used as the conditioned stimulus and unconditioned stimulus, respectively. Subjects with Met/Met homozygotes showed less fear acquisition (p

Diphenyl-benzo[1,3]dioxole-4-carboxylic acid pentafluorophenyl ester: a convenient catechol precursor in the synthesis of siderophore vectors suitable for antibiotic Trojan horse strategies

Catechols are components of many metal-chelating compounds, including siderophores that are naturally occurring iron(III) chelators excreted by microorganisms. Catechol derivatives are poorly soluble in organic media and the synthesis of catechol-containing molecules requires the use of protected catechol precursors with improved organic solubility. We therefore developed 2,2-diphenyl-benzo[1,3]dioxole-4-carboxylic acid pentafluorophenyl ester. This activated ester reacts with an amine functionalized scaffold to generate chelators in which the catechol functions are protected in the form of diphenyl-benzodioxole moieties. The catechol can subsequently be deprotected, at the end of the synthesis, with trifluoroacetic acid (TFA). This strategy was applied to the synthesis of two catechol compounds functionalized with a terminal propargyl extension. These two compounds were shown to promote iron uptake in Escherichia coli and Pseudomonas aeruginosa. These two compounds are suitable for use as vectors in antibiotic Trojan horse approaches, as they could be conjugated with azide-functionalized antibiotics using the Huisgen dipolar 1,3-cycloaddition.

Reversible Layer‐by‐Layer Deposition on Solid Substrates Inspired by Mussel Byssus Cuticle

The protective coating on mussel (Mytilus galloprovincialis) byssus has attracted considerable research interest because of its excellent mechanical properties such as hardness and extensibility. These special properties are known to be highly related with specific interactions between mussel foot protein-1 and metal ions. In particular, the complexation between catechols in mfp-1 and iron(III) has been identified as a key interaction. This finding has given opportunities for pursuing promising applications. Herein, we report that emulating the properties of the mussel byssus cuticle provides an important platform for developing reversible layer-by-layer (LbL) deposition, an advanced technique for surface modification. LbL films were constructed on solid substrates by sequential immersion of substrates into solutions containing iron(III) and catecholic compounds. The thickness of the LbL films was effectively controlled by increasing the immersion steps, and the reversibility of the LbL deposition was demonstrated by addition of a chelating agent.

Inhibitor Tolerance: A Comparison between Rhizopus sp. and Saccharomyces cerevisiae

Zygomycetes fungi are able to produce ethanol, and their biomass may hold a high market value, making them interesting microorganisms from a biorefinery perspective. In the present study, the inhibitor tolerance of the Zygomycetes fungus Rhizopus sp. was evaluated and compared with a flocculating strain of Saccharomyces cerevisiae. The inhibitors furfural, 5-hydroxymethylfurfural [HMF], acetic acid, and levulinic acid and the phenolic compounds catechol, guaiacol, and vanillin were applied in different combinations in a semi-synthetic medium. Glucose uptake and conversion of HMF in the presence of inhibitors were analyzed for the two organisms, and it appeared that the inhibitor resistances of Rhizopus sp. and S. cerevisiae were comparable. However, in the presence of catechol (0.165 g L-1), guaiacol (0.186 g L-1), and vanillin (0.30 g L-1), the glucose uptake by S. cerevisiae was only 3.5% of its uptake in a medium without inhibitors, while under equal conditions, Rhizopus sp. maintained 43% of its uninhibited glucose uptake.

Natural Abiotic Formation of Oxalic Acid in Soils: Results from Aromatic Model Compounds and Soil Samples

Oxalic acid is the smallest dicarboxylic acid and plays an important role in soil processes (e.g., mineral weathering and metal detoxification in plants). We have first proven its abiotic formation in soils and investigated natural abiotic degradation processes based on the oxidation of soil organic matter, enhanced by Fe(3+) and H(2)O(2) as hydroxyl radical suppliers. Experiments with the model compound catechol and further hydroxylated benzenes were performed to examine a common degradation pathway and to presume a general formation mechanism of oxalic acid. Two soil samples were tested for the release of oxalic acid and the potential effects of various soil parameters on oxalic acid formation. Additionally, the soil samples were treated with different soil sterilization methods to prove the oxalic acid formation under abiotic soil conditions. Different series of model experiments were conducted to determine a range of factors including Fe(3+), H(2)O(2), reaction time, pH, and chloride concentration on oxalic acid formation. Under certain conditions, catechol is degraded up to 65.6% to oxalic acid referring to carbon. In serial experiments with two soil samples, oxalic acid was produced, and the obtained results are suggestive of an abiotic degradation process. In conclusion, Fenton-like conditions with low Fe(3+) concentrations and an excess of H(2)O(2) as well as acidic conditions were required for an optimal oxalic acid formation. The presence of chloride reduced oxalic acid formation.

Crystallization and preliminary crystallographic analysis of 2-aminophenol 1,6-dioxygenase complexed with substrate and with an inhibitor.

Dioxygen activation implemented by nonhaem Fe(II) enzymes containing the 2-His-1-carboxylate facial triad has been extensively studied in recent years. Extradiol dioxygenase is the archetypal member of this superfamily and catalyzes the oxygenolytic ring opening of catechol analogues. Here, the crystallization and preliminary X-ray analysis of 2-aminophenol 1,6-dioxygenase, an enzyme representing a minor subset of extradiol dioxygenases that catalyze the fission of 2-aminophenol rather than catecholic compounds, is reported. Crystals of the holoenzyme with FeII and of complexes with the substrate 2-aminophenol and the suicide inhibitor 4-nitrocatechol were grown using the cocrystallization method under the same conditions as used for the crystallization of the apoenzyme. The crystals belonged to space group C2 and diffracted to 2.3-2.7 Å resolution; the crystal that diffracted to the highest resolution had unit-cell parameters a=270.24, b=48.39, c=108.55 Å, β=109.57°. All X-ray data sets collected from diffraction-quality crystals were suitable for structure determination.

Mollusk Glue Inspired Mucoadhesives for Biomedical Applications

Chitosan (CH), partially N-deacetylated chitin, is a biodegradable and biocompatible polymer that has shown great potential in drug delivery and tissue engineering applications. Although bioadhesive, CH has limited mucoadhesion in wet conditions due to weak interactions with biological surfaces. DOPA (3,4-dihydroxy-L-phenylalanine), a catechol-containing molecule naturally present in marine mussel foot proteins, has been shown to increase the mucoadhesion of several polymers. We report here a simple and bioinspired approach to enhance CH mucoadhesion in wet conditions by preparing mixed hydrogels including CH and different catechol-containing compounds, namely DOPA, hydrocaffeic acid (HCA), and dopamine (DA). We characterized the hydrogels for their swelling, release kinetics of the catechol compounds, and mucoadhesive strength to rabbit small intestine. The swelling of the hydrogels was pH dependent with maximum swelling at pH 1. The hydrogel swelling was higher in the presence of the DOPA and DA but lower in the presence of HCA. HCA/CH hydrogel also showed the slowest catechol release, most likely due to electrostatic interactions between CH and HCA. Lower hydrogel swelling and slower HCA release resulted in increased mucoadhesion: HCA/CH showed more than 2-fold enhancement of mucoadhesion to rabbit small intestine compared to CH alone. Since it is known that catechol compounds can be oxidized, we analyzed the oxidation of DOPA, HCA, and DA at different pH values and its effect on mucoadhesion. We found that oxidation occurring before contact with the intestinal mucosa did not improve mucoadhesion, while oxidation occurring during the contact further increased the mucoadhesion of HCA/CH hydrogels. These results show that mucoadhesion of CH hydrogels can be increased with a simple bioinspired approach, which has the potential to be applied to other polymers since it does not require any chemical modification.

Enzymatic oxidative transformation of phenols by Trametes trogii laccases

The removal of toxic phenolic compounds from industrial wastewater is an important issue to be addressed. Their presence in water and soil has become a great environmental concern, and effective methods for their removal need to be addressed. The feasibility of applying laccases for the degradation of phenolic compounds has received increasing attention. In the present work, the transformation of five phenolic compounds (catechol, hydroxytyrosol, tyrosol, guaiacol and p-coumaric acid), the main constituents of a typical wastewater derived from an olive oil factory, by Trametes trogii laccases was studied at concentrations ranging between 0.2 and 1.6 mM. High-performance liquid chromatography analysis showed high degradation rates of phenolic compounds by T. trogii laccases. Independently of the used concentration, a complete transformation of guaiacol, p−coumaric acid, hydroxytyrosol and tyrosol occurred after 1 h of incubation. The transformation of catechol depends on its initial concentration. The liquid chromatography-mass spectrometry analysis showed that laccases catalysed transformation of p-coumaric acid and tyrosol, resulting in the formation of phenolic dimers. No reduction of enzyme activity has been observed during the oxidation of all phenolic compounds. These results suggest that the studied laccases were capable of efficiently removing phenolic compounds, as well as catalysing the production of novel phenolic dimers.

Synthesis of Biologically Active Catecholic Compounds via ortho-Selective Oxygenation of Phenolic Compounds Using Hypervalent Iodine(V) Reagents

Catecholic motifs are present in numerous natural products and synthetic compounds used in various sectors of the chemical industries such as food, cosmetic, pharmaceutical and polymer industries. The antioxidant activity usually conferred to compounds bearing catecholic motifs is the property on which their application is often based. Although several (bio) chemical methods are available to chemists to produce catechols, the oxygenation of phenols constitutes one of the most practical approaches as long as the orthoselectivity of the process can be controlled. In this context, oxygenating hypervalent iodine(V) reagents offer a convenient metal-free solution. Among these reagents, 2-iodoxybenzoic acid (IBX) or its stabilized (non explosive) SIBX and polymer-supported versions have found the most useful and successful applications in the conversion of phenols into ortho-quinones, followed by reduction into catechols. Examples of oxygenative demethylation of 2-methoxyphenols and ortho-hydroxylation of phenolic compounds for the synthesis of biologically and industrially-relevant catechols are highlighted in this review article, together with some mechanistic discussions on these transformations. Keywords: Ortho-hydroxylation, Ortho-quinones, catechols, hypervalent iodine(V) reagents, Iodylarenes, 2-Iodoxybenzoic acid (IBX), stabilized 2-Iodoxybenzoic acid (SIBX), polymer-supported IBX, ortho-oxygenations, catecholic

Study of Electrochemical Oxidation of Catechol Derivatives in the Presence of 1-Phenyl-3-Methyl-5-Pyrazolone as a Nucleophile

Recently, 1-phenyl-3-methyl-5-pyrazolone (PMP) 9 and its methoxy analog, 1-(p-methoxy)-phenyl-3-methyl-5-pyrazolone (PMPMP) 10 have been used for pre-column derivatization of carbohydrates. The nucleophilic activity of these compounds is well known. 11,12 The electrochemical synthesis of organic compounds is a wellestablished technique and has been widely implemented for syntheses ofmaterialsthatarenotaccessiblebyconventionalmethods. 5 Electrochemical methods for the synthesis of organic compounds are green methods that utilize environmentally friendly solvents, a great advantage of these methods. 13 In addition, it is possible to monitor the synthesis process by electrochemical methods. 14 In the present work electrochemical activity of catechol compounds was studied in the presence of 1-phenyl-3-methyl-5pyrazolone as a nucleophile and the reaction mechanism was monitored by means of cyclic voltammetry and controlled-potential coulometry. The products were synthesized by an electrochemical method and characterized by means of FT-IR, 1 HNMR, 13 CNMR, MS spectroscopy and elemental analysis. The products were obtained in good yields and high purity. Theses materials might be used as analgesics in medical applications. 15

Synthesis and Structure/Antioxidant Activity Relationship of Novel Catecholic Antioxidant Structural Analogues to Hydroxytyrosol and Its Lipophilic Esters

A large panel of novel catecholic antioxidants and their fatty acid or methyl carbonate esters has been synthesized in satisfactory to good yields through a 2-iodoxybenzoic acid (IBX)-mediated aromatic hydroxylation as the key step. The new catechols are structural analogues of naturally occurring hydroxytyrosol (3,4-DHE). To evaluate structure/activity relationships, the antioxidant properties of all catecholic compounds were evaluated in vitro by ABTS assay and on whole cells by DCF fluorometric assay and compared with that of the corresponding already known hydroxytyrosyl derivatives. Results outline that all of the new catechols show antioxidant capacity in vitro higher than that of the corresponding hydroxytyrosyl derivatives. Less evident positive effects have been detected in whole cells experiments. Cytotoxicity experiments, using MTT assay, on a representative set of compounds evidenced no influence in cell survival.

Ultraviolet B radiation differentially modifies catechol‐O‐methyltransferase activity in keratinocytes and melanoma cells

Catechol-O-methyltransferase (COMT) is a ubiquitous enzyme inactivating catecholic compounds. COMT is expressed also in human skin samples, and in melanoma cells it may be cytoprotective. A role of COMT in keratinocytes (HaCat) is unknown. The objective of this study is: to investigate whether ultraviolet-B (UVB) radiation modifies COMT activity in melanocytes and HaCat and whether COMT inhibition plays a role in UVB-induced cell death. Human cell lines of melanotic melanoma (SK-mel-1) and HaCat were used. COMT activity was evaluated under basal conditions and after UVB irradiation (311 nm) at a low (8 mJ/cm(2)) and a high dose (60 mJ/cm(2)). Tolcapone 1 μM was used to inhibit COMT. Both SK-mel-1 and Ha-Cat cells express COMT activity. In SK-mel-1, COMT activity is reduced nearly 50% both 24 h and 48 h after a high dose UVB. In Ha-Cat cells, COMT activity increased 24 h after a high dose UVB but decreased at 48 h. Tolcapone increases significantly the cytotoxic effect of high dose UVB irradiation only in HaCat. High concentrations of tolcapone reduced melanin levels in melanoma cells parallel to reduced cell numbers. Ultraviolet radiation differentially modifies COMT activity in melanoma cells and HaCat. Furthermore, tolcapone increased death of HaCat after irradiation but did not affect melanoma cells.

Chemical characterisation of humic-like substances from urban, rural and tropical biomass burning environments using liquid chromatography with UV/vis photodiode array detection and electrospray ionisation mass spectrometry

Environmental contextOne of the most important classes of water-soluble organic compounds in continental fine and tropical biomass burning aerosol is humic-like substances (HULIS), which contain components with strong polar, acidic and chromophoric properties. We focus on the chemical characterisation of HULIS and provide evidence that nitro-aromatic catecholic compounds are among the major species of HULIS. This indicates that volatile aromatic hydrocarbons emitted during biomass burning are important gas-phase precursors for HULIS. AbstractHumic-like substances (HULIS) are ubiquitously present in the troposphere and make up a major fraction of continental fine-sized water-soluble organic compounds. They are regarded as material with strong polar, acidic and chromophoric properties; however, structural information at the individual component level is rather limited. In the present study, we have characterised HULIS from different locations using liquid chromatography coupled to photodiode array detection and negative ion electrospray ionisation mass spectrometry. Aerosol samples with particles less than 2.5 μm in diameter (PM2.5) were collected in Budapest and K-puszta, Hungary, during 2007 and 2008 spring and summer periods, and in Rondônia, Brazil, during a 2002 biomass burning experiment. Major components of the Budapest 2007 and Brazil 2002 HULIS corresponded to chromophoric substances, of which 4-nitrocatechol (molecular weight (MW) 155) was identified as the most abundant organic species and less abundant ones were attributed to mono- and dimethyl nitrocatechols (MWs 169 and 183). The mass concentrations of 4-nitrocatechol in the water-soluble organic carbon (WSOC) of the Budapest 2007 and day- and night-time Brazil 2002 HULIS were 0.46, 0.50 and 1.80 %. Abundant components of K-puszta 2008 HULIS were assigned to α-pinene secondary organic aerosol (SOA) tracers, i.e. 3-methyl-1,2,3-butanetricarboxylic acid and terpenylic acid; their mass concentrations in the HULIS WSOC were 0.75 and 0.40 %. Tere- and ortho-phthalic acids (MW 166) were major components of the Budapest and K-puszta HULIS, but only minor ones of the Brazil 2002 biomass burning HULIS, consistent with a source that is different from biomass burning and likely related to open waste burning of phthalate ester-containing material such as plastic.

Ferrocenyl catechols: synthesis, oxidation chemistry and anti-proliferative effects on MDA-MB-231 breast cancer cells

The synthesis and anti-tumoral properties of a series of compounds possessing a ferrocenyl group tethered to a catechol via a conjugated system is presented. On MDA-MB-231 breast cancer cell lines, the catechol compounds display a similar or greater anti-proliferative potency (IC(50) values ranging from 0.48-1.21 μM) than their corresponding phenolic analogues (0.57-12.7 μM), with the highest activity found for species incorporating the [3]ferrocenophane motif. On the electrochemical timescale, phenolic compounds appear to oxidize to the quinone methide, while catechol moieties form the o-quinone by a similar mechanism. Chemical oxidation of selected compounds with Ag(2)O confirms this interpretation and demonstrates the probable involvement of such oxidative metabolites in the in vitro activity of these species.

A seven-transmembrane receptor that mediates avoidance response to dihydrocaffeic acid, a water-soluble repellent in Caenorhabditis elegans.

The ability to detect harmful chemicals rapidly is essential for the survival of all animals. In Caenorhabditis elegans (C. elegans), repellents trigger an avoidance response, causing animals to move away from repellents. Dihydrocaffeic acid (DHCA) is a water-soluble repellent and nonflavonoid catecholic compound that can be found in plant products. Using a Xenopus laevis (X. laevis) oocyte expression system, we identified a candidate dihydrocaffeic acid receptor (DCAR), DCAR-1. DCAR-1 is a novel seven-transmembrane protein that is expressed in the ASH avoidance sensory neurons of C. elegans. dcar-1 mutant animals are defective in avoidance response to DHCA, and cell-specific expression of dcar-1 in the ASH neurons of dcar-1 mutant animals rescued the defect in avoidance response to DHCA. Our findings identify DCAR-1 as the first seven-transmembrane receptor required for avoidance of a water-soluble repellent, DHCA, in C. elegans.

Optimization of 2,3-dihydroxybiphenyl 1,2-dioxygenase expression and its application for biosensor

In this study, two statistical experimental designs, Plackett–Burman design (PBD) and response surface methodology (RSM), were employed to enhance the expression of 2,3-dihydroxybiphenyl 1,2-dioxygenase (BphC_LA-4), which was subsequently used for the construction of catechol biosensor. Ten important factors were evaluated by PBD, and four significant parameters were then optimized by RSM. Under the favorable fermentation conditions, the maximal specific activity of BphC_LA-4 was about 0.58U/mg with catechol as substrate. Meanwhile, homology modeling and molecular docking were utilized to help understand the interaction between BphC_LA-4 and catecholic substrates, which illustrated that BphC_LA-4 presented lower binding affinity towards 4-methylcatechol in comparison with 3-methylcatechol and catechol. Interestingly, the BphC_LA-4 enzyme electrode prepared by SiO2 sol–gel showed good response to all these three catecholic compounds. The differences of selectivity to 4-methylcatechol between free and immobilized enzyme implied that the introduction of electro-catalysis might have an effect on the enzyme-catalysis process.