Glucose hydrochar consists of linked phenol, furan, arene, alkyl, and ketone structures revealed by advanced solid-state nuclear magnetic resonance.

The molecular structure of hydrochars produced from 13C-enriched glucose under various conditions has been elucidated based on advanced one- and two-dimensional (2D) 1H-13C and 13C-13C solid-state nuclear magnetic resonance (NMR) with spectral editing. Regardless of synthesis conditions, hydrochars consist mostly of oxygen-substituted arene rings (including diphenols) and furans connected by alkyl linkers rich in ketones. Cross-linking nonprotonated and methyne (C-H) alkyl carbons have been identified through spectrally edited 2D NMR. Alkenes and 'quaternary' C-O are observed only at low synthesis temperature, while some clusters of fused arene rings are generated at high temperature. Hydrochar composition is nearly independent of reaction time in the range from 1 to 5 h. Equilibration of 13C magnetization within 1 s shows that the materials are homogeneous on the 5-nm scale, refuting core-shell models of hydrochar microspheres. While furan C-O carbons bonded to alkyl groups or ketones show distinctive cross peaks in 2D NMR, phenolic C-OH is observed unambiguously by hydroxyl-proton selection. While methylene-linked furan rings are fairly common, the signal previously assigned to furan Cα-Cα linkages is shown to arise from abundant, stable catecholic ortho-diphenols, whose HO-C=C-OH structure is proved by 2D13C-13C NMR after hydroxyl-proton selection. Quantitative 13C NMR spectra of low- and high-temperature hydrochars have been matched by chemical-shift simulations for representative structural models. Mixed phenol and furan rings connected by ketones and alkyl linkers provide good fits of the experimental spectra, while literature models dominated by large clusters of fused rings and with few phenols or alkyl-linked ketones do not.

The Invisible Fraction within Melanin Capable of Absorbing UV Light and with Fluorescent Properties: Is It Lacking Consideration?

Expanding on earlier observations, we show that many melanin materials, in vitro synthesized from a wide range of precursors, can be fractionated into a dark-colored precipitate and a near-colorless, dispersible fraction. The dispersible fractions exhibited absorbance in the UVA and UVB range of the electromagnetic spectrum, but none in the visible range. In addition, fluorescent properties were associated with all dispersible fractions obtained. FT-IR spectroscopic analyses were performed to compare both types of fractions. Overall, it appears that some of the properties associated with melanin (UV absorbance, fluorescence) may not necessarily reside in the dark-colored portion of melanin, but in a colorless fraction of the material. It remains to be seen whether any of these in vitro observations have any relevance in vivo. However, we raise the possibility that the presence of a colorless fraction within melanin materials and their associated properties may have received inadequate attention. Given the important association between melanin, UV protection, and skin cancer, it is worthwhile to consider this additional aspect of melanin chemistry.

A Cationic Catechol Derivative Binds Anions in Competitive Aqueous Media.

A simple dihydroxy isoquinolinium molecule (3+) was prepared by a modification of a literature procedure. Interestingly, during optimisation of the synthesis a small amount of the natural product pseudopalmatine was isolated, and characterised for the first time by X-ray crystallography. Compound 3+ contains a catechol motif and positive charge on the same scaffold and was found to be a potent anion receptor, binding sulfate strongly in 8 : 2 d6-acetone:D2O and 7 : 3 d6-acetone:D2O (Ka>104 and 2,100 M-1, respectively). Unsurprisingly, chloride binding was much weaker, even in the less polar solvent mixture 9 : 1 d6-acetone:D2O. The sulfate binding is remarkably strong for such a simple molecule, however anion binding studies were complicated by the tendency of the molecule to react with BPh4 - or BF4 - species during anion metathesis reactions. This gave two unusual zwitterions containing tetrahedral boronate centres, which were both characterised by X-ray crystallography.

Lipid Peroxidation and Antioxidant Protection.

Lipid peroxidation (LP) is the most important type of oxidative-radical damage in biological systems, owing to its interplay with ferroptosis and to its role in secondary damage to other biomolecules, such as proteins. The chemistry of LP and its biological consequences are reviewed with focus on the kinetics of the various processes, which helps understand the mechanisms and efficacy of antioxidant strategies. The main types of antioxidants are discussed in terms of structure-activity rationalization, with focus on mechanism and kinetics, as well as on their potential role in modulating ferroptosis. Phenols, pyri(mi)dinols, antioxidants based on heavy chalcogens (Se and Te), diarylamines, ascorbate and others are addressed, along with the latest unconventional antioxidant strategies based on the double-sided role of the superoxide/hydroperoxyl radical system.

Advances in 4-Hydroxyphenylacetate-3-hydroxylase Monooxygenase.

Catechols have important applications in the pharmaceutical, food, cosmetic, and functional material industries. 4-hydroxyphenylacetate-3-hydroxylase (4HPA3H), a two-component enzyme system comprising HpaB (monooxygenase) and HpaC (FAD oxidoreductase), demonstrates significant potential for catechol production because it can be easily expressed, is highly active, and exhibits ortho-hydroxylation activity toward a broad spectrum of phenol substrates. HpaB determines the ortho-hydroxylation efficiency and substrate spectrum of the enzyme; therefore, studying its structure-activity relationship, improving its properties, and developing a robust HpaB-conducting system are of significance and value; indeed, considerable efforts have been made in these areas in recent decades. Here, we review the classification, molecular structure, catalytic mechanism, primary efforts in protein engineering, and industrial applications of HpaB in catechol synthesis. Current trends in the further investigation of HpaB are also discussed.

The Influence of Catechols on the Magnetization of Iron Oxide Nanoparticles.

In this study, MNPs were functionalized with pyrocatechol (CAT), pyrogallol (GAL), caffeic acid (CAF), and nitrodopamine (NDA) at pH 8 and pH 11. The functionalization of the MNPs was successful, except in the case of NDA at pH 11. The thermogravimetric analyses indicated that the surface concentration of the catechols was between 1.5 and 3.6 molecules/nm2. The saturation magnetizations (Ms) of the functionalized MNPs were higher than the starting material. XPS analyses showed only the presence of Fe(III) ions on the surface, thus refuting the idea of the Fe being reduced and magnetite being formed on the surfaces of the MNPs. Density functional theory (DFT) calculations were performed for two modes of adsorption of CAT onto two model surfaces: plain and adsorption via condensation. The total magnetization of both adsorption modes remained the same, indicating that the adsorption of the catechols does not affect the Ms. The analyses of the size and the size distribution showed an increase in the average size of the MNPs during the functionalization process. This increase in the average size of the MNPs and the reduction in the fraction of the smallest (i.e., <10 nm) MNPs explained the increase in the Ms values.

Inhibitory activity of catecholic phosphonic and phosphinic acids against Helicobacter pylori ureolysis.

Catechols have been reported to be potent covalent inhibitors of ureases, and they exhibit activity by modifying cysteine residues at the entrance to enzymatic active sites. Following these principles, we designed and synthesized novel catecholic derivatives that contained carboxylate and phosphonic/phosphinic functionalities and assumed expanded specific interactions. When studying the chemical stability of the molecules, we found that their intrinsic acidity catalyzes spontaneous esterification/hydrolysis reactions in methanol or water solutions, respectively. Regarding biological activity, the most promising compound, 2-(3,4-dihydroxyphenyl)-3-phosphonopropionic acid (15), exhibited significant anti-urease potential (Ki = 2.36 µM, Sporosarcinia pasteurii urease), which was reflected in the antiureolytic effect in live Helicobacter pylori cells at a submicromolar concentration (IC50 = 0.75 µM). As illustrated by molecular modeling, this compound was bound in the active site of urease through a set of concerted electrostatic and hydrogen bond interactions. The antiureolytic activity of catecholic phosphonic acids could be specific because these compounds were chemically inert and not cytotoxic to eukaryotic cells.

Phytochemical and Antioxidant Profile of the Medicinal Plant Melia azedarach Subjected to Water Deficit Conditions.

Environmental stress triggered by climate change can alter the plant's metabolite profile, which affects its physiology and performance. This is particularly important in medicinal species because their economic value depends on the richness of their phytocompounds. We aimed to characterize how water deficit modulated the medicinal species Melia azedarach's lipophilic profile and antioxidant status. Young plants were exposed to water deficit for 20 days, and lipophilic metabolite profile and the antioxidant capacity were evaluated. Leaves of M. azedarach are rich in important fatty acids and oleamide. Water deficit increased the radical scavenging capacity, total phenol, flavonoids, and catechol pools, and the accumulation of ß-sitosterol, myo-inositol, succinic acid, sucrose, d-glucose and derivatives, d-psicofuranose, d-(+)-fructofuranose, and the fatty acids stearic, α-linolenic, linoleic and palmitic acids. These responses are relevant to protecting the plant against climate change-related stress and also increase the nutritional and antioxidant quality of M. azedarach leaves.

Cytotoxicity inhibition of catechol's type molecules by grafting on TiO2 and Fe2O3 nanoparticles surface.

The potential toxicity deriving from the interaction between chemicals and manufactured nanoparticles (NPs) represents an emerging threat to the environment and human health. Several studies have focused on the risks and (eco)toxicity of manufactured NPs as a consequence of their extensive use in recent years, however, there is still a limited understanding of the combined effects caused by manufactured NPs in the presence of other environmental contaminants. This is particularly relevant to aquatic environments, where many types of pollutants are inevitably released and can be involved in many kinds of reactions. In this context, the interaction between catecholate type ligands and two different nanomaterials, namely TiO2 and Fe2O3 NPs, was investigated by performing cytotoxicity assays with the topminnow fish hepatoma cell line (PLHC-1) using: i) the original organic molecules, ii) pristine NPs alone, and iii) modified NPs obtained by grafting the ligands on the NPs surface. Cytotoxic effects were explored at three different levels, specifically on cellular metabolism, membrane integrity and lysosomal activity. The outcomes from these assays showed cytotoxicity only for the free catechol type ligands, while in general no significant decrease in cell viability was observed for pristine NPs, as well as for the modified NPs, regardless the initial cytotoxicity level of the organic ligands These results suggest that the binding of catechols on the NPs' surface inhibited their cytotoxicity, indicating that TiO2 and Fe2O3 NPs may act as sorbents of these contaminants, thus reducing their possible detrimental effects.

Pd-catalyzed Aerobic Cross-Dehydrogenative Coupling of Catechols with 2-Oxindoles and Benzofuranones: Reactivity Difference Between Monomer and Dimer.

Persistent radicals, which are generated from 2-oxindole or benzofuranone dimers, are useful tools for designing the radical-based cross-coupling reaction to provide molecules containing a quaternary carbon. The persistent radical is accessible from both the dimer and monomer; however, the reactivity difference between these substrates for the oxidative cross-coupling reaction is not fully understood, most likely because of the mechanistic complexity. Here, we present details of an aerobic cross-dehydrogenative coupling (CDC) reaction using various monomers and catechols. UV-Vis analysis and mechanistic control experiments showed that the monomer is less reactive than the dimer under aerobic conditions. Our Pd(II)-BINAP-µ-hydroxo complex significantly improved the reactivity of the monomers for the aerobic CDC reaction with catechols, yielding results comparable to those of the corresponding dimer. The procedure, which enables the generation of the persistent radical in situ, is particularly useful when employing the monomer that is not readily converted to the corresponding dimer.

Study on the Neuroprotective, Radical-Scavenging and MAO-B Inhibiting Properties of New Benzimidazole Arylhydrazones as Potential Multi-Target Drugs for the Treatment of Parkinson's Disease.

Oxidative stress is a key contributing factor in the complex degenerating cascade in Parkinson's disease. The inhibition of MAO-B affords higher dopamine bioavailability and stops ROS formation. The incorporation of hydroxy and methoxy groups in the arylhydrazone moiety of a new series of 1,3-disubstituted benzimidazole-2-thiones could increase the neuroprotective activity. In vitro safety evaluation on SH-SY5Y cells and rat brain synaptosomes showed a strong safety profile. Antioxidant and neuroprotective effects were evaluated in H2O2-induced oxidative stress on SH-SY5Y cells and in a model of 6-OHDA-induced neurotoxicity in rat brain synaptosomes, where the dihydroxy compounds 3h and 3i demonstrated the most robust neuroprotective and antioxidant activity, more pronounced than the reference melatonin and rasagiline. Statistically significant MAO-B inhibitory effects were exerted by some of the compounds where again the catecholic compound 3h was the most potent inhibitor similar to selegiline and rasagiline. The most potent antioxidant effect in the ferrous iron induced lipid peroxidation assay was observed for the three catechols-3h and 3j, 3q. The catecholic compound 3h showed scavenging capability against superoxide radicals and antioxidant effect in the iron/deoxyribose system. The study outlines a perspective multifunctional compound with the best safety profile, neuroprotective, antioxidant and MAO-B inhibiting properties.

Monitoring bioaccessibility of iron and zinc in pearl millet grain after sequential milling.

The present study was to understand the effect of sequential milling on the distribution of inhibitory factors and their relation to iron-zinc bioaccessibility in the two pearl millet cultivars differing in grain shape and size. The studies revealed that the yield of decorticated grain and bran fractions differed between the cultivars. The initial bran fractions had lower iron content, which increased on increase of decortication duration (2.33-25.14 mg/100 g), while zinc did not follow this pattern. Among the inhibitory factors, polyphenols and phytic acid were low in the initial stages of milling and subsequently increased as the milling duration increased. Microscopic studies further confirmed that iron-zinc and inhibitory factors coexist in the same tissues of the grain. The ß- carotene was more concentrated in the middle layers of the pericarp. It was observed that iron bioaccessibility was the highest in the 4 min milling bran (7.7%, 3.34%) and final decorticated grain fractions (13.79%, 18.45%) of both the cultivars. Iron bioaccessibility could not be related to any particular inhibitory factors, in bran insoluble fibre and phytic acid were prominent while in decorticated grain galloyls, catechols and phytic acid were the maxima. In both the cultivars, zinc bioaccessibility was high in fractions with low phytic acid and insoluble fibre. The data presented suggest that 6 min decortication that removed around 10-15% of the bran had the highest iron and zinc bioaccessibility. The iron-rich bran fraction after appropriate processing can also be used in speciality food and thereby addresses the problem of micronutrient deficiency. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13197-021-05072-x.

Multiple catechols in human plasma after drinking caffeinated or decaffeinated coffee.

BACKGROUND: Coffee is one of the most frequently consumed beverages worldwide. Research on effects of coffee drinking has focused on caffeine; however, coffee contains myriad biochemicals that are chemically unrelated to caffeine, including 3,4-dihydroxyphenyl compounds (catechols) such as caffeic acid and dihydrocaffeic acid (DHCA). OBJECTIVE: This prospective within-subjects study examined effects of drinking caffeinated or decaffeinated coffee on plasma free (unconjugated) catechols measured by liquid chromatography with series electrochemical detection (LCED) after batch alumina extraction. To confirm coffee-related chromatographic peaks represented catechols, plasma was incubated with catechol-O-methyltransferase and S-adenosylmethionine before the alumina extraction; reductions in peak heights would identify catechols. METHODS: Ten healthy volunteers drank 2 cups each of caffeinated and decaffeinated coffee on separate days after fasting overnight. With subjects supine, blood was drawn through an intravenous catheter up to 240 min after coffee ingestion and the plasma assayed by alumina extraction followed by LCED. RESULTS: Within 15 min of drinking coffee of either type, >20 additional peaks were noted in chromatographs from the alumina eluates. Most of the coffee-related peaks corresponded to free catechols. Plasma levels of the catecholamines epinephrine and dopamine increased with both caffeinated and decaffeinated coffee. Levels of other endogenous catechols were unaffected. Plasma DHCA increased bi-phasically, in contrast with other coffee-related free catechols. INTERPRETATION: Drinking coffee-whether caffeinated or decaffeinated-results in the rapid appearance of numerous free catechols in the plasma. These might affect the disposition of circulating catecholamines. The bi-phasic increase in plasma DHCA is consistent with production by gut bacteria.

The critical role of unique azido-substituted chloro-O-semiquinone radical intermediates in the synergistic toxicity between sodium azide and chlorocatecholic carcinogens.

We have shown previously that exposing bacteria to tetrachlorocatechol (TCC) and sodium azide (NaN3) together causes synergistic cytotoxicity in a biphasic mode. However, the underlying chemical mechanism remains unclear. In this study, an unexpected ring-contraction 3(2H)-furanone and two quinoid-compounds were identified as the major and minor reaction products, respectively; and two unusual azido-substituted chloro-O-semiquinone radicals were detected and characterized as the major radical intermediates by complementary applications of direct ESR, HPLC/ESI-Q-TOF and high-resolution MS studies with nitrogen-15 isotope-labeled NaN3. Taken together, we proposed a novel molecular mechanism for the reaction of TCC/NaN3: N3- may attack on tetrachloro-O-semiquinone radical, forming two transient 4-azido-3,5,6-trichloro- and 4,5-diazido-3,6-dichloro-O-semiquinone radicals, consecutively. The second-radical intermediate may either undergo an unusual zwitt-azido cleavage to form the less-toxic ring-contraction 3(2H)-furanone product, or further oxidize to form the more toxic quinoid-product 4-amino-5-azido-3,6-dichloro-O-benzoquinone. A good correlation was observed between the biphasic formation of this toxic quinone due to the two competing decomposition pathways of the radical intermediate and the biphasic synergism between TCC and NaN3, which are dependent on their molar-ratios. This is the first report of detection and identification of two unique azido-substituted chloro-O-semiquinone radicals, and an unprecedented ring-contraction mechanism via an unusually mild and facile zwitt-azido rearrangement.

Effects of the Reactive Moiety of Phenolipids on Their Antioxidant Efficiency in Model Emulsified Systems.

Our previous research was focused on the effects of hydrophobicity on the antioxidant (AO) efficiency of series of homologous antioxidants with the same reactive moieties. In this work we evaluate the antioxidant efficiency of hydrophobic phenolipids in 4:6 olive oil-in-water emulsions, with different phenolic moieties (derived from caffeic, 4-hydroxycinnamic, dihydrocaffeic acids, tyrosol and hydroxytyrosol), with alkyl chains of 8 and 16 carbons, and compare the antioxidant efficiency with that of the parent compounds. All catecholic phenolipids, in particular the C8 derivatives, have proven to be better antioxidants for the oxidative protection of emulsions than their parental compounds with octyl dihydrocafffeate being the most efficient (16-fold increase in relation to the control). To understand the importance of some factors on the antioxidant efficiency of compounds in emulsions, Pearson's correlation analysis was carried out between antioxidant activity and the first anodic potential (Epa), reducing capacity (FRAP value), DPPH radical scavenging activity (EC50) and the concentration of antioxidants in each region of the emulsified system. Results confirm the importance of the effective concentration of AOs in the interfacial region (AOI) (ρ = 0.820) and of the Epa (ρ = -0.677) in predicting their antioxidant efficiency in olive oil-in-water emulsions.

Interactive Materials for Bidirectional Redox-Based Communication.

Emerging research indicates that biology routinely uses diffusible redox-active molecules to mediate communication that can span biological systems (e.g., nervous and immune) and even kingdoms (e.g., a microbiome and its plant/animal host). This redox modality also provides new opportunities to create interactive materials that can communicate with living systems. Here, it is reported that the fabrication of a redox-active hydrogel film can autonomously synthesize a H2 O2 signaling molecule for communication with a bacterial population. Specifically, a catechol-conjugated/crosslinked 4-armed thiolated poly(ethylene glycol) hydrogel film is electrochemically fabricated in which the added catechol moieties confer redox activity: the film can accept electrons from biological reductants (e.g., ascorbate) and donate electrons to O2 to generate H2 O2 . Electron-transfer from an Escherichia coli culture poises this film to generate the H2 O2 signaling molecule that can induce bacterial gene expression from a redox-responsive operon. Overall, this work demonstrates that catecholic materials can participate in redox-based interactions that elicit specific biological responses, and also suggests the possibility that natural phenolics may be a ubiquitous biological example of interactive materials.

Hierarchical chitinous matrices byssus-inspired with mechanical properties tunable by Fe(III) and oxidation.

In this study the multi-scale hierarchical structure of the ß-chitin matrix from squid pen of Loligo vulgaris was used as substrate to synthesize new bio-inspired materials. Aiming to mimic the byssus peculiar mechanical properties, we chemically functionalized the ß-chitin matrix with catechols, one of the main functional groups of the byssus. The obtained matrix preserved its multi-scale structural organization and was able to chelate reversibly Fe(III). Thus, it behaved as the byssus, acting as a metal cross-linkable matrix that upon metalation increased its Young's modulus, E (>10 times). The functionalized matrix was also cross-linked by oxidation provoking an increase of the E (>10 times) and first failure stress (>5 times). The oxidation of the functionalized matrix followed by metalation slightly increased the material mechanical properties. In conclusion, we added specific bio-functionalities in a natural matrix tuning its mechanical properties without altering its multi-scale organization.

Inhibition of Urease, a Ni-Enzyme: The Reactivity of a Key Thiol With Mono- and Di-Substituted Catechols Elucidated by Kinetic, Structural, and Theoretical Studies.

The inhibition of urease from Sporosarcina pasteurii (SPU) and Canavalia ensiformis (jack bean, JBU) by a class of six aromatic poly-hydroxylated molecules, namely mono- and dimethyl-substituted catechols, was investigated on the basis of the inhibitory efficiency of the catechol scaffold. The aim was to probe the key step of a mechanism proposed for the inhibition of SPU by catechol, namely the sulfanyl radical attack on the aromatic ring, as well as to obtain critical information on the effect of substituents of the catechol aromatic ring on the inhibition efficacy of its derivatives. The crystal structures of all six SPU-inhibitors complexes, determined at high resolution, as well as kinetic data obtained on JBU and theoretical studies of the reaction mechanism using quantum mechanical calculations, revealed the occurrence of an irreversible inactivation of urease by means of a radical-based autocatalytic multistep mechanism, and indicate that, among all tested catechols, the mono-substituted 3-methyl-catechol is the most efficient inhibitor for urease.

Chemical Reactivities of ortho-Quinones Produced in Living Organisms: Fate of Quinonoid Products Formed by Tyrosinase and Phenoloxidase Action on Phenols and Catechols.

Tyrosinase catalyzes the oxidation of phenols and catechols (o-diphenols) to o-quinones. The reactivities of o-quinones thus generated are responsible for oxidative browning of plant products, sclerotization of insect cuticle, defense reaction in arthropods, tunichrome biochemistry in tunicates, production of mussel glue, and most importantly melanin biosynthesis in all organisms. These reactions also form a set of major reactions that are of nonenzymatic origin in nature. In this review, we summarized the chemical fates of o-quinones. Many of the reactions of o-quinones proceed extremely fast with a half-life of less than a second. As a result, the corresponding quinone production can only be detected through rapid scanning spectrophotometry. Michael-1,6-addition with thiols, intramolecular cyclization reaction with side chain amino groups, and the redox regeneration to original catechol represent some of the fast reactions exhibited by o-quinones, while, nucleophilic addition of carboxyl group, alcoholic group, and water are mostly slow reactions. A variety of catecholamines also exhibit side chain desaturation through tautomeric quinone methide formation. Therefore, quinone methide tautomers also play a pivotal role in the fate of numerous o-quinones. Armed with such wide and dangerous reactivity, o-quinones are capable of modifying the structure of important cellular components especially proteins and DNA and causing severe cytotoxicity and carcinogenic effects. The reactivities of different o-quinones involved in these processes along with special emphasis on mechanism of melanogenesis are discussed.

Inhibiting NF-κB-Mediated Inflammation by Catechol-Type Diphenylbutadiene via an Intracellular Copper- and Iron-Dependent Pro-Oxidative Role.

Chronic inflammation mediated by nuclear factor-κB (NF-κB) plays a crucial role in the development of cancer. As part of our continuous efforts placed on investigating anticancer mechanisms of dietary catechols, we further applied catechol-type diphenylbutadiene (3,4-DHB) as a model molecule to probe whether it inhibits inflammation by its pro-oxidative role. Employing lipopolysaccharide-stimulated RAW264.7 cells as a model of inflammation, we validated that benefiting from its catechol moiety, 3,4-DHB inhibited significantly the LPS-induced formation of NO (11.48 ± 0.39 µM) compared with the only LPS-stimulated group (31.8 ± 1.78 µM) with an inhibitory rate of 64% at 5 µM, expression of iNOS and COX-2 proteins, phosphorylation of IkB kinase and IkBα, and nuclear translocation of NF-κB. Noticeably, its inhibitory activity against the NF-κB-mediated inflammation can be obviously revised by pretreatment of the cells with dithiothreitol (a quencher of both electrophilic o-quinone and ROS), neocuproine (a specific chelating agent for copper ions), and deferoxamine (a specific chelating agent for iron ions). The above results support that depending on intracellular copper and iron ions, 3,4-DHB, a pro-electrophile, can be converted into its corresponding o-quinone electrophile together with the generation of ROS, a pro-oxidative event that mediates its inhibitory activity against NF-κB signaling and inflammation. The copper- and iron-dependent inhibition against inflammation supports that dietary catechols are probably pro-oxidative anti-inflammatory agents.