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Cytochromes P450 (CYPs) are heme-thiolate monooxygenases that prototypically catalyze the insertion of oxygen into unactivated C-H bonds but are capable of mediating more complex reactions. One of the most remarked-upon alternative reactions occurs during biosynthesis of the gibberellin A (GA) phytohormones, involving hydrocarbon ring contraction with coupled aldehyde extrusion of ent-kaurenoic acid to form the first gibberellin intermediate. While the unusual nature of this reaction has long been noted, its mechanistic basis has remained opaque. Building on identification of the relevant CYP114 from bacterial GA biosynthesis, detailed structure-function studies are reported here, including development of in vitro assays as well as crystallographic analyses both in the absence and presence of substrate. These structures provided insight into enzymatic catalysis of this unusual reaction, as exemplified by identification of a key role for the "missing" acid from an otherwise highly conserved acid-alcohol pair of residues. Notably, the results demonstrate that ring contraction requires dual factors, both the use of a dedicated ferredoxin and absence of the otherwise conserved acidic residue, with exclusion of either limiting turnover to just the initiating and more straightforward hydroxylation. The results provide detailed insight into the enzymatic structure-function relationships underlying this fascinating reaction and support the use of a semipinacol mechanism for the unusual ring contraction reaction. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Lobophorins (LOBs) belong to a large family of spirotetronate antibiotics with antibacterial and antitumor activities. In this study, we demonstrated the function of LobP1, a P450 monooxygenase encoded in the LOB biosynthetic gene cluster, by in vivo deletion and in vitro biochemical assays. The disruption of lobP1 led to the isolation of three new LOBs derivatives (3—5) and three known ones (6—8) without the hydroxyl group at C‐32. LobP1 was shown to have relatively broad substrate scope. Determining the kinetic parameters of LobP1 towards different substrates revealed that LobP1 preferred substrate with a nitrosugar. The new LOBs 3—5 displayed significant antibacterial activities against Bacillus subtilis and Micrococcus luteus with MIC values of 0.125 to 1 μg·mL–1, and the major product LOB E (6) from the ∆lobP1 mutant showed moderate cytotoxic activities against several cancer cell lines. [ABSTRACT FROM AUTHOR]

A highly efficient protocol was developed for the ipso hydroxylation of arylboronic acids using citric acid as an effective organocatalyst. The sustainable methodology offers good to excellent yields with in the rapid reaction time in water as a solvent media and 30% H2O2 as an oxidant. The reaction proceeds without the aid of any metal catalyst or base and is simple, safe, and clean. The current protocol enables the access to variety of phenols and is found to be tolerable to the diverse electronic substrates. Even, the devised reaction conditions have been found to be effective in the gram-scale synthesis of an API, Mequinol. [ABSTRACT FROM AUTHOR]

A peroxygenase‐catalysed hydroxylation of organosilanes is reported. The recombinant peroxygenase from Agrocybe aegerita (AaeUPO) enabled efficient conversion of a broad range of silane starting materials in attractive productivities (up to 300 mM h−1), catalyst performance (up to 84 s−1 and more than 120 000 catalytic turnovers). Molecular modelling of the enzyme‐substrate interaction puts a basis for the mechanistic understanding of AaeUPO selectivity. [ABSTRACT FROM AUTHOR]

Herein, we have demonstrated Lewis acid Fe(III)-assisted hydroxylation of ZIF-67 to form FexCo-layered double hydroxide (LDH) nanosheets. The catalyst Fe0.4Co-LDH produced an excellent water oxidation activity to reach a current density of 20 mA cm−2 at only 190 mV overpotential, superior to that of hydrothermally synthesized LDH with a similar composition. [ABSTRACT FROM AUTHOR]

Caffeine is a natural compound found in plant seeds that after consumption by humans effects the central nervous system as well as the cardiovascular system. In general, the cytochrome P450 enzymes in the liver are involved in the biodegradation of caffeine, which gives paraxanthine, theobromine and theophylline products. There has been debate for many years why multiple products are obtained and how their distributions are determined. To this end we performed a high‐level computational study using a combination of molecular dynamics and quantum mechanical approaches. A series of quantum chemical cluster models on the mechanism of caffeine activation by P450 model complexes give hydrogen atom abstraction barriers that predicts the correct ordering and statistical distribution of products. Our studies highlight that second‐coordination sphere effects and thermochemical properties of the substrate determine the product distributions. [ABSTRACT FROM AUTHOR]

Prolyl hydroxylase domain (PHD) enzymes change HIF activity according to oxygen signal; whether it is regulated by other physiological conditions remains largely unknown. Here, we report that PHD3 is induced by fasting and regulates hepatic gluconeogenesis through interaction and hydroxylation of CRTC2. Pro129 and Pro615 hydroxylation of CRTC2 following PHD3 activation is necessary for its association with cAMP-response element binding protein (CREB) and nuclear translocation, and enhanced binding to promoters of gluconeogenic genes by fasting or forskolin. CRTC2 hydroxylation-stimulated gluconeogenic gene expression is independent of SIK-mediated phosphorylation of CRTC2. Liver-specific knockout of PHD3 (PHD3 LKO) or prolyl hydroxylase-deficient knockin mice (PHD3 KI) show attenuated fasting gluconeogenic genes, glycemia, and hepatic capacity to produce glucose during fasting or fed with high-fat, high-sucrose diet. Importantly, Pro615 hydroxylation of CRTC2 by PHD3 is increased in livers of fasted mice, diet-induced insulin resistance or genetically obese ob/ob mice, and humans with diabetes. These findings increase our understanding of molecular mechanisms linking protein hydroxylation to gluconeogenesis and may offer therapeutic potential for treating excessive gluconeogenesis, hyperglycemia, and type 2 diabetes. [ABSTRACT FROM AUTHOR]

Diphenyl ethers (DEs), which are widely used in the agricultural and chemical industries, have become hazardous contaminants in the environment. Although several DE-degrading bacteria have been reported, discovering new types of such microorganisms could enhance understanding of the degradation mechanism in the environment. In this study, we used a direct screening method based on detection of ether bond–cleaving activity to screen for microorganisms that degrade 4,4′-dihydroxydiphenyl ether (DHDE) as a model DE. Microorganisms isolated from soil samples were incubated with DHDE, and strains producing hydroquinone via ether bond cleavage were selected using hydroquinone-sensitive Rhodanine reagent. This screening procedure resulted in the isolation of 3 bacteria and 2 fungi that transform DHDE. Interestingly, all of the isolated bacteria belonged to one genus, Streptomyces. To our knowledge, these are the first microorganisms of the genus Streptomyces shown to degrade a DE. Streptomyces sp. TUS-ST3 exhibited high and stable DHDE-degrading activity. HPLC, LC-MS, and GC–MS analyses revealed that strain TUS-ST3 converts DHDE to its hydroxylated analogue and generates hydroquinone as an ether bond–cleavage product. Strain TUS-ST3 also transformed DEs other than DHDE. In addition, glucose-grown TUS-ST3 cells began to transform DHDE after incubation with this compound for 12 h, and produced 75 μM hydroquinone in 72 h. These activities of streptomycetes may play an important role in DE degradation in the environment. We also report the whole genome sequence of strain TUS-ST3. [Display omitted] • Streptomyces strains transforming DEs were discovered for the first time. • Streptomyces sp. TUS-ST3 generated hydroquinone as an ether bond cleavage product of DHDE. • Strain TUS-ST3 also exhibited transforming activity toward DEs other than DHDE. [ABSTRACT FROM AUTHOR]

In this work, we have systematically reviewed the till date disclosed routes pertaining to the synthesis of Parvaquone. Prior art search gave us around nineteen synthetic routes, involving invention and innovation towards the starting material selection and process path to synthesize Parvaquone. Interestingly, 2-hydroxy naphthalene-1,4-dione has been the predominant raw material used for the synthesis of Parvaquone. Every process was executed to attain higher atom economy, process economy, and better purity of the product. In most of the works, a significant focus was given on choosing cheap and easy-to-obtain raw materials/reagents. In the past six years, we have noticed the disclosure of mainly single and two-step processes with simple and mild reaction conditions for the preparation of Parvaquone. Only a few researchers had given an importance for the recovery and reuse of high-cost raw materials/reagents/solvents along with effluent management. If these aspects were collectively considered during the process development of drug, then the disclosed synthetic routes would become well accomplished for large-scale manufacturing. SYNOPSIS In this review work, we have gathered nineteen till date synthetic approaches of Parvaquone from the prior art disclosures. For the beneficial commercialization of Paravaquone, single or two-step processes would be favorable. This will provide much-needed control over the process of large-scale drug manufacturing. [ABSTRACT FROM AUTHOR]

To overcome the limitations of ZnO as a photocatalyst, the present work reports a ternary nanocomposite (ZnO–TiO2/rGO) with a high photocatalytic activity under direct natural solar light irradiation. Reduced graphene oxide (rGO) was obtained after bio-reduction of GO using pomegranate peels. Techniques of FE-SEM, TEM, XRD, FTIR, UV–Vis DRS, Raman and PL were used for characterization purpose. The ternary nanocomposite exhibited a high photocatalytic activity towards the degradation of indigo carmine dye, resulting in an efficiency of 92% within 150 min under sunlight illumination. Accordingly, the hybridization of ZnO with TiO2 and rGO improves light absorption, promotes high separation of photogenerated charges, and solves the photocorrosion drawback of ZnO, leading to a better stability and reusability of the nanocomposite. Particularly, the prepared rGO allowed certain hydrophilicity and a better surface hydroxylation. In view of that, a comprehensive photocatalytic mechanism was proposed and discussed, referred to experiments showing the effect of holes and •OH scavengers. The findings revealed that the developed rGO hybridized with ZnO–TiO2 heterojunction can be a promising candidate for removing environmental contaminations using natural solar light. [ABSTRACT FROM AUTHOR]

The silica gel promoted straightforward remote para‐C−H hydroxylation of aryl‐urea derivatives under metal‐free mild conditions by using diacetoxyiodobenzene as oxidant has been developed. Replacing the Lewis acids with silica gel effectively improved the tolerance of functional groups and resulted in a wide range of target compounds with various substituents in moderate to excellent yields. Moreover, this transformation has been demonstrated that could more effectively and conveniently synthesize pharmaceutical and biomedical compounds which contain 4‐hydroxyarlyurea skeleton. [ABSTRACT FROM AUTHOR]

Background: A large portion of idiopathic and familial dilated cardiomyopathy (DCM) cases have no obvious causal genetic variant. Although altered response to metabolic stress has been implicated, the molecular mechanisms underlying the pathogenesis of DCM remain elusive. The JMJD family proteins, initially identified as histone deacetylases, have been shown to be involved in many cardiovascular diseases. Despite their increasingly diverse functions, whether JMJD family members play a role in DCM remains unclear. Methods: We examined Jmjd4 expression in patients with DCM, and conditionally deleted and overexpressed Jmjd4 in cardiomyocytes in vivo to investigate its role in DCM. RNA sequencing, metabolites profiling, and mass spectrometry were used to dissect the molecular mechanism of Jmjd4-regulating cardiac metabolism and hypertrophy. Results: We found that expression of Jmjd4 is significantly decreased in hearts of patients with DCM. Induced cardiomyocyte-specific deletion of Jmjd4 led to spontaneous DCM with severely impaired mitochondrial respiration. Pkm2, the less active pyruvate kinase compared with Pkm1, which is normally absent in healthy adult cardiomyocytes but elevated in cardiomyopathy, was found to be drastically accumulated in hearts with Jmjd4 deleted. Jmjd4 was found mechanistically to interact with Hsp70 to mediate degradation of Pkm2 through chaperone-mediated autophagy, which is dependent on hydroxylation of K66 of Pkm2 by Jmjd4. By enhancing the enzymatic activity of the abundant but less active Pkm2, TEPP-46, a Pkm2 agonist, showed a significant therapeutic effect on DCM induced by Jmjd4 deficiency, and heart failure induced by pressure overload, as well. Conclusions: Our results identified a novel role of Jmjd4 in maintaining metabolic homeostasis in adult cardiomyocytes by degrading Pkm2 and suggest that Jmjd4 and Pkm2 may be therapeutically targeted to treat DCM, and other cardiac diseases with metabolic dysfunction, as well. [ABSTRACT FROM AUTHOR]

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is known to be a tobacco-specific N-nitrosamine and has peripheral carcinogenic properties. It can also induce oxidative stress, glial cell activation, and neuronal damage in the brain. However, the distribution and metabolic characteristics of NNK in the central nervous system are still unclear. Here, a sensitive and effective UHPLC-HRMS/MS method was established to identify and investigate the metabolites of NNK and their distribution in the rat brain. In addition, the pharmacokinetic profiles were simultaneously investigated via blood–brain synchronous microdialysis. NNK and its seven metabolites were well quantified in the hippocampus, cortex, striatum, olfactory bulb, brain stem, cerebellum, and other regions of rat brain after peripheral exposure (5 mg/kg, i.p.). The average content of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in all brain regions was at least threefold higher than that of NNK, indicating a rapid carbonyl reduction of NNK in the brain. Lower concentrations of pyridine N-oxidation products in the cortex, olfactory bulb, hippocampus, and striatum might be related to the poor detoxification ability in these regions. Compared to α-methyl hydroxylation, NNK and NNAL were more inclined to the α-methylene hydroxylation pathway. Synchronous pharmacokinetic results indicated that the metabolic activity of NNK in the brain was different from that in the blood. The mean α-hydroxylation ratio in the brain and blood was 0.037 and 0.161, respectively, which indicated poor metabolic activity of NNK in the central nervous system. [ABSTRACT FROM AUTHOR]

The cytochrome P450 (CYP) enzyme family is the major enzyme system catalyzing the phase I metabolism of xenobiotics, including pharmaceuticals and toxic compounds in the environment. A major part of the CYP-dependent xenobiotic metabolism is due to polymorphic and inducible enzymes, which may, quantitatively or qualitatively, alter or enhance drug metabolism and toxicity. Drug–drug interactions are major mechanisms caused by the inhibition and/or induction of CYP enzymes. Particularly, CYP monooxygenases catalyze hydroxylation reactions to form hydroxylated metabolites. The secondary metabolites are sometimes as active as the parent compound, or even more active. The aim of this review is to summarize some of the significative examples of common drugs used for the treatment of diverse diseases and underline the activity and/or toxicity of their metabolites. [ABSTRACT FROM AUTHOR]

In this perspective, two different classes of multidentate ligands (aminotriphenolate and dipyridinimine) and the corresponding metal (Ti, V, Mo, W, Fe) complexes are described. These catalysts can activate efficiently the environmental benign H2O2 oxidant, promoting a wide variety of oxidative processes (sulfoxidations, N‐oxidations, epoxidations, haloperoxidation, alcohol oxidation, hydroxylation). [ABSTRACT FROM AUTHOR]

In this perspective, two different classes of multidentate ligands (aminotriphenolate and dipyridinimine) and the corresponding metal (Ti, V, Mo, W, Fe) complexes are described. These catalysts can activate efficiently the environmental benign H2O2 oxidant, promoting a wide variety of oxidative processes (sulfoxidations, N‐oxidations, epoxidations, haloperoxidation, alcohol oxidation, hydroxylation). [ABSTRACT FROM AUTHOR]

Peroxodicarbonate represents a green and largely underexplored oxidizer generated electrochemically from aqueous carbonate solutions. Through state‐of‐the‐art electrolyzer technology, highly concentrated solutions have now become accessible. These were successfully employed as green oxidizer in deborolative hydroxylations. A plethora of phenols and alcohols have thus been synthesized in up to 99 % from organoboron compounds using only green and non‐toxic solvents. This transformation was successfully scaled‐up to multi‐gram batch sizes. [ABSTRACT FROM AUTHOR]

Fe (II)-and 2-ketoglutarate-dependent dioxygenases (Fe (II)/α-KG DOs) have been applied to catalyze hydroxylation of amino acids. However, the Fe (II)/α-KG DOs that have been developed and characterized are not sufficient. L-isoleucine dioxygenase (IDO) is an Fe (II)/α-KG DO that specifically catalyzes the formation of 4-hydroxyisoleucine (4-HIL) from L-isoleucine (L-Ile) and exhibits a substrate specificity toward L-aliphatic amino acids. To expand the substrate spectrum of IDO toward aromatic amino acids, in this study, we analyzed the regularity of the substrate spectrum of IDO using molecular dynamics (MD) simulation and found that the distance between Fe2+, C2 of α-KG and amino acid chain's C4 may be critical for regulating the substrate specificity of the enzyme. The mutation sites (Y143, S153 and R227) were also subjected to single point saturation mutations based on polarity pockets and residue free energy contributions. It was found that Y143D, Y143I and S153A mutants exhibited catalytic L-phenylalanine activity, while Y143I, S153A, S153Q and S153Y exhibited catalytic L-homophenylalanine activity. Consequently, this study extended the substrate spectrum of IDO with aromatic amino acids and enhanced its application property. [ABSTRACT FROM AUTHOR]

Collagen, the most abundant organic compound of vertebrate organisms, is a supramolecular, protein-made polymer. Details of its post-translational maturation largely determine the mechanical properties of connective tissues. Its assembly requires massive, heterogeneous prolyl-4-hydroxylation (P4H), catalyzed by Prolyl-4-hydroxylases (P4HA1–3), providing thermostability to its elemental, triple helical building block. So far, there was no evidence of tissue-specific regulation of P4H, nor of a differential substrate repertoire of P4HAs. Here, the post-translational modifications of collagen extracted from bone, skin, and tendon were compared, revealing lower hydroxylation of most GEP/GDP triplets, together with fewer other residue positions along collagen a chains, in the tendon. This regulation is mostly conserved in two distant homeotherm species, mouse and chicken. The comparison of detailed P4H patterns in both species suggests a two-step mechanism of specificity. P4ha2 expression is low in tendon and its genetic invalidation in the ATDC5 cellular model of collagen assembly specifically mimics the tendon-related P4H profile. Therefore, P4HA2 has a better ability than other P4HAs to hydroxylate the corresponding residue positions. Its local expression participates in determining the P4H profile, a novel aspect of the tissue specificities of collagen assembly. [ABSTRACT FROM AUTHOR]

The world's consumption of raw materials has shifted from the use of non‐renewable materials to renewable materials. Studies on greener epoxidation using vegetable oils to produce eco‐friendly polyol have also increased. This study aims to produce polyol‐based epoxidized palm oleic acid with a high hydroxyl value by a novel method which is continuous hydroxylation of epoxidized palm oleic acid using a heterogeneous catalyst. Starting from the raw palm oleic acid, the double bonds are functionalized by introducing epoxy groups and ring‐opened to produce hydroxyl groups. The best process parameters for epoxidation were optimized to maximize the oxirane value and to focus on oxirane stability. The relative conversion to the oxirane percentage was maximum (82%) after 30 min of epoxidation reaction. Fourier transform infrared spectroscopy showed an absorption peak at a wavelength of 3300 cm−1, indicating the presence of a hydroxyl group when polyol was analyzed. Overall, polyol with a high hydroxyl value (339 mg KOH/g), high yield (80.7%) and average molecular weight of 1045 Da was successfully produced from palm oleic acid using continuous hydroxylation of epoxidized oleic acid. Based on hydroxyl value and average molecular weight, the polyol is deemed suitable for producing rigid polyurethane foam. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study focused on developing and characterizing an emulsion paint formulated from a copolymer binder of polyvinyl acetate-hydroxylated guna seed oil (PVAc/HGSO) and compared with paint made from conventional polyvinyl acetate (PVAc) binder. Seed oil from guna was extracted mechanically using cold press method, and the extracted guna oil were successively subjected to epoxidation and hydroxylation reaction processes. The hydroxylated guna seed oil (HGSO) was copolymerised with conventional polyvinyl acetate in different ratio of 10 to 70% of hydroxylated oil, to formulate a novel PVAc/HGSO copolymer binder. The formulated copolymer binder was characterised, and compared with the standard inorder to ascertain the better blend ratio that will be suitable for paint production. The better blend copolymer binder was used in production of an emulsion paint. The physico-chemical parameters on the formulated emulsion paint were compared with paint formulated using only PVAc as a binder and acceptable value in the coating industry. The novel formulated emulsion paint found to be increased in gloss, adhesion and flexibility, which are major setback in paint produced using conventional PVAc only as a binder. [ABSTRACT FROM AUTHOR]

The enhanced mechanochemical reactivity of potassium hydroxide (KOH) in the presence of 18-crown-6 ether is supported by potassium complexation under milling and has been demonstrated in the Henry reaction and SNAr hydroxylation: in both cases, the desired product is formed within 10 minutes, but requires the presence of the crown ether. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) have developed as a potential advanced variety of catalysts wherein copper SACs (Cu SACs) have appeared as a rising star in catalysis in which promising catalytic activity is achieved by a well-adjusted d-band center. Herein, the most recent advancements in the synthesis of copper SACs are highlighted. Various electrocatalytic applications such as carbon dioxide reduction reaction, oxygen reduction reaction, nitrogen reduction reaction, biotherapeutic applications, coupling reactions, hydroxylation, hydrogenation, photocatalytic reactions, and other miscellaneous reactions of Cu SACs coordinated into different supports have been thoroughly reviewed, and the stability and electrocatalytic performance of Cu SACs in fuel cells, zinc–CO2 batteries, and zinc–air batteries have been discussed. This review summarizes the study of most recent developments in the synthesis and applications of Cu SACs. [ABSTRACT FROM AUTHOR]

Ribosomal protein uL15 (RPL27a) carries a specific modification, hydroxylation, at the His39 residue, which neighbors the CCA terminus of the E-site-bound tRNA at the mammalian ribosome. Under hypoxia, the level of hydroxylation of this protein decreases. We transiently transfected HEK293T cells with constructs expressing wild-type uL15 or mutated uL15 (His39Ala) incapable of hydroxylation, and demonstrated that ribosomes containing both proteins are competent in translation. By applying RNA-seq to the total cellular and polysome-associated mRNAs, we identified differentially expressed genes (DEGs) in cells containing exogenous uL15 or its mutant form. Analyzing mRNA features of up- and down-regulated DEGs, we found an increase in the level of more abundant mRNAs and shorter CDSs in cells with uL15 mutant for both translated and total cellular mRNAs. The level of longer and rarer mRNAs, on the contrary, decreased. Our data show how ribosome heterogeneity can change the composition of the translatome and transcriptome, depending on the properties of the translated mRNAs. [ABSTRACT FROM AUTHOR]

l‐Proline hydroxylase is a member of the non‐heme Fe2+/α‐ketoglutarate (AKG)‐dependent hydroxylase family that catalyzes the reaction from l‐proline to hydroxy‐l‐proline, which is widely used in drug synthesis, biochemistry, food supplementation and cosmetic industries. Here, the first crystal structure of l‐proline trans‐hydroxylase and its complexes with substrate and product are reported, which reveal the structural basis of trans–cis proline hydroxylation selectivity. Structure comparison with other AKG‐dependent hydroxylases identifies conserved amino acid residues, which may serve as signatures of in‐line or off‐line AKG binding modes in the AKG‐dependent enzyme family. [ABSTRACT FROM AUTHOR]

Scale‐up of oxygenase catalyzed reactions is often challenging due to the limited oxygen mass transfer in aqueous solutions. To overcome such limitation, we studied different scale‐up conditions using recombinant resting cells of E. coli JM109(DE3), harboring the cumene dioxygenase of Pseudomonas fluorescens IP01, for the dihydroxylation of naphthalene to (1R,2S)‐cis‐1,2‐dihydro‐1,2‐naphthalenediol. Thereby, vigorous stirring of the biotransformation in a 2 L round bottom flask in combination with an oxygen‐enriched headspace exhibited outstanding product formation after 1 h. Furthermore, the enhanced setup was used for the cumene dioxygenase catalyzed biosynthesis of 240 mg of valuable (+)‐trans‐carveol from (R)‐(+)‐limonene, demonstrating the application of our workflow for volatile compounds. [ABSTRACT FROM AUTHOR]

The developing nervous system is remarkably sensitive to environmental signals, including disruptive toxins, such as polybrominated diphenyl ethers (PBDEs). PBDEs are an environmentally pervasive class of brominated flame retardants whose neurodevelopmental toxicity mechanisms remain largely unclear. Using dissociated cortical neurons from embryonic Rattus norvegicus, we found here that chronic exposure to 6-OH-BDE-47, one of the most prevalent hydroxylated PBDE metabolites, suppresses both spontaneous and evoked neuronal electrical activity. On the basis of our previous work on mitogen-activated protein kinase (MAPK)/extracellular signal-related kinase (ERK) (MEK) biology and our observation that 6-OH-BDE-47 is structurally similar to kinase inhibitors, we hypothesized that certain hydroxylated PBDEs mediate neurotoxicity, at least in part, by impairing the MEK-ERK axis of MAPK signal transduction. We tested this hypothesis on three experimental platforms: 1) in silico, where modeling ligand-protein docking suggested that 6-OH-BDE-47 is a promiscuous ATP-competitive kinase inhibitor; 2) in vitro in dissociated neurons, where 6-OH-BDE-47 and another specific hydroxylated BDE metabolite similarly impaired phosphorylation of MEK/ERK1/2 and activity-induced transcription of a neuronal immediate early gene; and 3) in vivo in Drosophila melanogaster, where developmental exposures to 6-OH-BDE-47 and a MAPK inhibitor resulted in offspring displaying similarly increased frequency of mushroom-body β-lobe midline crossing, a metric of axonal guidance. Taken together, our results support that certain ortho-hydroxylated PBDE metabolites are promiscuous kinase inhibitors and can cause disruptions of critical neurodevelopmental processes, including neuronal electrical activity, pre-synaptic functions, MEK-ERK signaling, and axonal guidance.

mTORC1 is an important regulator of muscle mass but how it is modulated by oxygen and nutrients is not completely understood. We show that loss of the prolyl hydroxylase domain isoform 1 oxygen sensor in mice (PHD1KO) reduces muscle mass. PHD1KO muscles show impaired mTORC1 activation in response to leucine whereas mTORC1 activation by growth factors or eccentric contractions was preserved. The ability of PHD1 to promote mTORC1 activity is independent of its hydroxylation activity but is caused by decreased protein content of the leucyl tRNA synthetase (LRS) leucine sensor. Mechanistically, PHD1 interacts with and stabilizes LRS. This interaction is promoted during oxygen and amino acid depletion and protects LRS from degradation. Finally, elderly subjects have lower PHD1 levels and LRS activity in muscle from aged versus young human subjects. In conclusion, PHD1 ensures an optimal mTORC1 response to leucine after episodes of metabolic scarcity.

Exposures to persistent organohalogen chemicals during pregnancy are associated with adverse health effects. Low-income, minority women with pre-existing co-morbidities may be particularly vulnerable to these exposures, but have historically been understudied. We aimed to characterize exposures to multiple chemical classes among a sample of ethnically diverse, lower income, overweight or obese pregnant women. Serum concentrations of polybrominated diphenyl ethers (PBDEs) and their hydroxylated metabolites (OH-PBDEs), polychlorinated biphenyls (PCBs), and poly- and perfluoroalkyl substances (PFASs) were measured in 98 pregnant women (California; 2011-2013). Aggregate exposures were evaluated using correlational clustering, a "chemical burden" score, and PCA. Associations between sociodemographic characteristics and individual and aggregate exposures were evaluated using multivariable linear regression. Clustering and PCA both produced four groupings: (PC1) PBDEs/OH-PBDEs, (PC2) PCBs, (PC3) PFNA/PFOA/PFDeA, (PC4) PFHxS/PFOS. Race/ethnicity and prepregnancy BMI were associated with PBDEs, OH-PBDEs and PC1. Maternal age was associated with PCBs and PC2. Parity was associated with PBDEs, OH-PBDEs and PC2. Poverty was negatively associated with PCBs, whereas food insecurity was positively associated with PFOS. We observed variations in sociodemographic profiles of exposures by chemical class and weak across-class correlations. These findings have implications for epidemiologic studies of chemical mixtures and for exposure reduction strategies.

Metabolic models can be useful for rapid identification of suitable analytical targets to aid in the detection of new psychoactive substances (NPS) in human biological samples. In vitro and in vivo metabolic studies of the synthetic cannabinoid ADB-4en-PINACA were carried out using zebrafish and rat liver microsome models. Seventeen phase-I metabolites, including seventeen metabolites generated from rat liver microsomes and fourteen metabolites from zebrafish, were identified and structurally characterized by liquid chromatography-high resolution mass spectrometry. The main metabolic pathways of the phase-I metabolism included hydroxylation, N-dealkylation, amide hydrolysis, ketone formation from the t-butyl and aliphatic chains, oxidation of the N-double-bond, amide hydrolysis combined with dehydrogenation, and amide hydrolysis followed by hydroxylation, as well as dehydrogenation and N-dealkylation. Hydroxylation (M3), ketone (M10), and dihydrodiol (M15) metabolites can be recommended as metabolic markers for ADB-4en-PINACA. These findings identify the zebrafish model as a promising tool for elucidating the metabolism of NPS., Author(s): Xinze Liu [sup.1] [sup.2], Wei Liu [sup.1], Ping Xiang [sup.1], Taijun Hang [sup.2], Yan Shi [sup.1], Linna Yue [sup.1], Hui Yan [sup.1] Author Affiliations: (1) Department of Forensic Toxicology, [...]

BackgroundHorehound (Marrubium vulgare) is a medicinal plant whose signature bioactive compounds, marrubiin and related furanoid diterpenoid lactones, have potential applications for the treatment of cardiovascular diseases and type II diabetes. Lack of scalable plant cultivation and the complex metabolite profile of M. vulgare limit access to marrubiin via extraction from plant biomass. Knowledge of the marrubiin-biosynthetic enzymes can enable the development of metabolic engineering platforms for marrubiin production. We previously identified two diterpene synthases, MvCPS1 and MvELS, that act sequentially to form 9,13-epoxy-labd-14-ene. Conversion of 9,13-epoxy-labd-14-ene by cytochrome P450 monooxygenase (P450) enzymes can be hypothesized to facilitate key functional modification reactions in the formation of marrubiin and related compounds.ResultsMining a M. vulgare leaf transcriptome database identified 95 full-length P450 candidates. Cloning and functional analysis of select P450 candidates showing high transcript abundance revealed a member of the CYP71 family, CYP71AU87, that catalyzed the hydroxylation of 9,13-epoxy-labd-14-ene to yield two isomeric products, 9,13-epoxy labd-14-ene-18-ol and 9,13-epoxy labd-14-ene-19-ol, as verified by GC-MS and NMR analysis. Additional transient Nicotiana benthamiana co-expression assays of CYP71AU87 with different diterpene synthase pairs suggested that CYP71AU87 is specific to the sequential MvCPS1 and MvELS product 9,13-epoxy-labd-14-ene. Although the P450 products were not detectable in planta, high levels of CYP71AU87 gene expression in marrubiin-accumulating tissues supported a role in the formation of marrubiin and related diterpenoids in M. vulgare.ConclusionsIn a sequential reaction with the diterpene synthase pair MvCPS1 and MvELS, CYP71AU87 forms the isomeric products 9,13-epoxy labd-14-ene-18/19-ol as probable intermediates in marrubiin biosynthesis. Although its metabolic relevance in planta will necessitate further genetic studies, identification of the CYP71AU87 catalytic activity expands our knowledge of the functional landscape of plant P450 enzymes involved in specialized diterpenoid metabolism and can provide a resource for the formulation of marrubiin and related bioactive natural products.

Surfactant controlling the wettability of reservoir rocks is one of the important ways to enhance oil recovery in low-permeability tight reservoirs. A large number of scholars have developed a series of excellent wettability control reagents through macro physical simulation experiments, but macro experiments are difficult to analyze the micro mechanism of liquid/liquid and liquid/solid interface action of reagents controlling rock wettability. In this paper, the wetting behavior of water molecules on silica surfaces modified with different hydroxylation, methylation and hydrophobic chain length was studied by molecular dynamics simulation, and the quantitative relationship between different modification degrees and wetting angle was established. The results show that the original wetting angle of silica is 58.5°, and the surface wettability can be changed from hydrophilic to hydrophobic through surface modification, with a wetting angle of 27.25°∼115.78°. With the increase of the coverage of hydrophobic methyl or hydrophilic hydroxyl modified groups, the wetting angle increases or decreases respectively. The quantitative relationship between modification degree and wetting angle was established by simulated data. With the increasing of the chain length of methyl group, the distance between water molecule and silica surface increases and the interaction decreases, which can improve the regulation effect of methyl group hydrophobicity. This paper provides a reference basis for the synthesis of rock wettability control reagent and the quantitative characterization of modification degree.

Two new tetradentate N4 ligands (LN4), LN4 = Me2,Me2PyzTACN (1-(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)-4,7-dimethyl-1,4,7-triazacyclononane) and Me2,MeImTACN (1-((1-methyl-1H-imidazol-1-yl)methyl)-4,7-dimethyl-1,4,7-triazacyclononane) have been synthesized and their corresponding Fe(II) complexes [FeII(Me2,Me2PyzTACN)(CF3SO3)2], 1Pz, and [FeII(Me2,MeImTACN)(CF3SO3)2], 1Im, have been prepared and characterized. Complexes 1Pz and 1Im catalyse the hydroxylation of C–H bonds of alkanes with excellent efficiencies, using hydrogen peroxide as oxidant. The high H/D kinetic isotope effect values for C–H hydroxylation, large normalized tertiary/secondary C–H (C3/C2) bond selectivities in adamantane oxidation, and high degrees of stereoretention in the oxidation of cis-1,2-dimethylcyclohexane are indicative of metal-based oxidation processes. The complexes also catalyse the oxidation of cyclooctene to form its corresponding epoxide and syn-diol. For 1Pz the epoxide is the main product, while for the analogous complex 1Im the syn-diol predominates. The active oxidant is proposed to be an [(LN4)FeV(O)(OH)]2+ species (2Pz, LN4 = Me2,Me2PyzTACN and 2Im, LN4 = Me2,MeImTACN) which may exist in two tautomeric forms related by a proton shift between the oxo and hydroxo ligands. Isotope labelling experiments show that the oxygen atom in the hydroxylated products originates from both water and hydrogen peroxide, and labelling experiments involving oxygen atom transfer to sterically bulky substrates provide indirect information on the steric influence exerted by the two ligands in the relative reactivities of the two hypervalent iron tautomers. Based on these labelling studies, the steric influence exerted by each of the ligands towards the relative reactivity of the oxo ligands of the corresponding pair of Fe(V)(O)(OH) tautomers can be derived. Furthermore, this steric influence can be gauged relative to related complexes/ligands. [ABSTRACT FROM AUTHOR]

Natural products with the 3,6‐diene‐2,5‐diketopiperazine core are widely distributed in nature; however, the biosynthetic mechanism of 3,6‐diene‐2,5‐diketopiperazine in fungi remains to be further elucidated. Through heterologous expression and biochemical investigation of an FeII/2‐oxoglutarate‐dependent oxidase (AspE) and a heme‐dependent P450 enzyme (AspF), we report that AspE, AspF and subsequent dehydration account for the formation of the 3,6‐diene‐2,5‐diketopiperazine substructure of brevianamide K from Aspergillus sp. SK‐28, a symbiotic fungus of mangrove plant Kandelia candel. More interestingly, in‐depth investigation of the enzymatic mechanism showed that AspE promotes hydroxylation of brevianamide Q with unprecedented stereoinversion through hydrogen atom abstraction and water nucleophilic attack from the opposite face of the resultant iminium cation intermediate. [ABSTRACT FROM AUTHOR]

Fe(II) complexes with pentadentate ligands, including N-heterocyclic carbene moieties, were prepared and electrostatically attached onto the perfluorinated surface of a mesoporous aluminosilicate. The heterogeneous catalysts were applied to the catalytic oxidation of cyclohexane and cyclohexene using H2O2 as an oxidant in CH3CN, demonstrating high performance and selectivity in alkane hydroxylation and cyclohexene epoxidation. [ABSTRACT FROM AUTHOR]

A one-step method for the conversion of nitroarenes into phenols under operationally simple, transition-metal-free conditions is described. This denitrative functionalization protocol provides a concise and economical alternative to conventional three-step synthetic sequences. Experimental and computational studies suggest that nitroarenes may be substituted by an electron-catalysed radical-nucleophilic substitution (SRN1) chain mechanism. [ABSTRACT FROM AUTHOR]

The FeIII(OH)(Cl) complex resembles the key intermediate proposed for the non‐heme iron halogenases. Goldberg and co‐workers reported that the FeIII(OH)(Cl) RC reacts with triphenylmethyl radical 1 to give an exclusive hydroxylation product. To understand the chemoselectivity of the reaction of RC with 1, density functional theory (DFT) calculations have been conducted. From RC, the competing pathways were identified as the OH‐transfer, Cl‐transfer, and isomerization pathways. The direct Cl‐transfer is more favorable than direct OH‐transfer by 2.8 kcal/mol. The hydrogen bonding interactions between the hydroxyl group and the pendent amine ligand impede the direct OH‐transfer from RC. Compared with the direct Cl‐transfer pathway, the isomerization pathways require lower barriers. In isomer RCiso2, the equatorial hydroxyl group, which has smaller diabatic bond dissociation energy, prefers to transfer to form the hydroxylation product. In FeIII(Cl)2RC2 and RC2iso, the equatorial chloride group also prefers to transfer to give the chlorination product. [ABSTRACT FROM AUTHOR]

Previous studies on biocatalytic transformations of pinenes by cytochrome P450 (CYP) enzymes reveal the formation of different oxygenated products from a single substrate due to the multistate reactivity of CYP and the many reactive sites in the pinene scaffold. Up until now, the detailed mechanism of these biocatalytic transformations of pinenes have not been reported. Hereby, we report a systematic theoretical study of the plausible hydrogen abstraction and hydroxylation reactions of α- and β-pinenes by CYP using the density functional theory (DFT) method. All DFT calculations in this study were based on B3LYP/LAN computational methodology using the Gaussian09 software. We used the B3LYP functional with corrections for dispersive forces, BSSE, and anharmonicity to study the mechanism and thermodynamic properties of these reactions using a bare model (without CYP) and a pinene-CYP model. According to the potential energy surface and Boltzmann distribution for radical conformers, the major reaction products of CYP-catalyzed hydrogen abstraction from β-pinene are the doublet trans (53.4%) and doublet cis (46.1%) radical conformer at delta site. The formation of doublet cis/trans hydroxylated products released a total Gibbs free energy of about 48 kcal/mol. As for alpha pinene, the most stable radicals were trans-doublet (86.4%) and cis-doublet (13.6%) at epsilon sites, and their hydroxylation products released a total of ~50 kcal/mol Gibbs free energy. Our results highlight the likely C-H abstraction and oxygen rebounding sites accounting for the multi-state of CYP (doublet, quartet, and sextet spin states) and the formation of different conformers due to the presence of cis/trans allylic hydrogen in α-pinene and β-pinene molecules. [ABSTRACT FROM AUTHOR]

Our previous study found that high-dose Tanshinones Capsule (TC) aggravated cholestasis in mice. To explore its underlying mechanism, main tanshinones components (15,16-dihydrotanshinone I (DTI), cryptotanshinone (CTS) and tanshinone IIA (TSA)) form TC were studied separately. Bile acids (BAs) that were primarily metabolized by hydroxylation were identified, and then the inhibitory effect of each tanshinones on their hydroxylation were evaluated. The anti-cholestasis effect of each tanshinones were studied in mice, the hepatic concentrations of BAs and tanshinones were measured and analyzed as well. The effect of tanshinones on Cyp3a11 protein expression was investigated. DTI exhibited inhibitory effect on the hydroxylation of lithocholic acid (LCA), taurolithocholic acid (TLCA) and taurochenodeoxycholic acid (TCDCA), their IC 50 values were 0.81, 0.36 and 1.29 μM, respectively. The hydroxylation of LCA, TLCA and TCDCA were mediated by Cyp3a11. Low-dose DTI, CTS and TSA ameliorated cholestatic liver injury in mice, while high-dose DTI didn't exhibit anti-cholestatic effect. The hepatic BAs profiles indicated that hydroxylation of BAs was inhibited in high-dose DTI group. DTI and TSA up-regulated the protein expression of Cyp3a11. As the hepatic concentration of DTI increased, the inhibitory effect at enzymatic activity level overwhelmed its up-regulation effect at protein level, thus resulted in worsening of cholestasis. • DTI was responsible for the cholestasis caused by high-dose Tanshinones Capsule. • Cyp3a11-mediated hydroxylation was detoxification pathway of bile acids in mice. • DTI could up-regulate cyp3a11 protein expression in less dose-proportional manner. • High concentration of DTI could inhibit the hydroxylation activity of Cyp3a11. • Protein up-regulation was overwhelmed by enzyme activity inhibition by high-dose DTI. [ABSTRACT FROM AUTHOR]

The reaction of (NMe4)2[NiII(LPh)(OAc)] (1[OAc], LPh = 2,2′,2′′-nitrilo-tris-(N-phenylacetamide); OAc = acetate) with 3-chloroperoxybenzoic acid (m-CPBA) resulted in the formation of a self-hydroxylated NiIII-phenolate complex, 2, where one of the phenyl groups of LPh underwent hydroxylation. 2 was characterised by UV-Vis, EPR, and XAS spectroscopies and ESI-MS. 2 decayed to yield a previously characterised NiII-phenolate complex, 3. We postulate that self-hydroxylation was mediated by a formally NiIV＝O oxidant, formed from the reaction of 1[OAc] with m-CPBA, which undergoes electrophilic aromatic substitution to yield 2. This is supported by an analysis of the kinetic and thermodynamic properties of the reaction of 1[OAc] with m-CPBA. Addition of exogenous hydrocarbon substrates intercepted the self-hydroxylation process, producing hydroxylated products, providing further support for the formally NiIV＝O entity. This study demonstrates that the reaction between NiII salts and m-CPBA can lead to potent metal-based oxidants, in contrast to recent studies demonstrating carboxyl radical is a radical free-chain reaction initiator in NiII/m-CPBA hydrocarbon oxidation catalysis. [ABSTRACT FROM AUTHOR]

In recent years, many efforts have been made to epoxidize palm oil in response to rising demand for environmentally safe epoxides that generated from vegetable oils. This experiment has studied two methods: the one-step method (continuous epoxidation-hydroxylation) and the two-step method (a separate process of epoxidation followed by hydroxylation) for bio-polyol production. Based on the results of the experiment, the one-step technique experiment was deemed to be the best approach because it did not require for the process to be stopped and because it is a continuous process, it takes less time to manufacture the bio-polyol and costs less because the catalyst is only used once. The relative conversion to oxirane (RCO) percentage was at its maximum (82%) after 30 min of epoxidation reaction. FTIR spectroscopy shows the absorption peak at a wavelength of 3300 cm−1 indicates the presence of hydroxyl groups when polyol was analyzed. Overall, a polyol with a high yield was successfully produced from palm oleic acid by using continuous hydroxylation of epoxidized oleic acid. [ABSTRACT FROM AUTHOR]

Objective: Evaluate the influence of a polymeric catalyst primer (PCP) on esthetic efficacy (EE), degradation kinetics of hydrogen peroxide (H2O2), and trans‐amelodentinal cytotoxicity (TC) of bleaching gels. Materials and Methods: The following groups were established: G1: No treatment (NC, negative control); G2: PCP; G3: 10% H2O2; G4: PCP + 10% H2O2; G5: 20% H2O2; G6: PCP + 20% H2O2; G7: 35% H2O2 (positive control); G8: PCP + 35% H2O2. To determine EE, enamel/dentin discs (E/DDs) were stained and subjected or not to bleaching protocols for 45 min. To assess TC, the E/DDs were adapted to artificial pulp chambers. The extracts (culture medium + gel components diffused through E/DDs) were applied to odontoblast‐like MDPC‐23 cells. The viability (VB), oxidative stress (OxS), morphology (SEM), amount of H2O2 diffused and the production of hydroxyl radical (OH•) were assessed (two‐way ANOVA/Tukey/paired Student t‐test; p < 0.05). Results: The highest EE was found in G8 (p < 0.05), and G4, G6, and G7 did not differ statistically (p > 0.05). In G4, the limited H2O2 diffusion reduced OxS and increased cell VB (p < 0.05). Conclusions: Coating the enamel with PCP containing 10 mg/ml of manganese oxide before applying the 10% H2O2 bleaching gel maintains the EE of conventional in‐office bleaching and minimizes the toxic effects of this esthetic therapy. Clinical Significance: Coating the enamel with a PCP before applying the bleaching gel may potentiate the EE of the conventional in‐office tooth bleaching and reduce the toxicity of this professional therapy to the dental pulp. [ABSTRACT FROM AUTHOR]

This research proposed and validated an LC-MSMS method for five reduction and hydroxylation metabolites of Mequindox (MEQ) as well as the precursor in holothurian samples. Specially, three hydroxylation metabolites (2-isoethanol-mequindox, M3, 2-isoethanol-1-desoxymequindox, M4 and 2-isoethanol-4-desoxymequindox, M5) are novel for analysis. Target compounds were extracted with methanol and ethyl acetate in turn without any complicated acidolysis, alkaline hydrolysis or enzymolysis steps. Samples were further purified with C18 solid-phase extraction cartridges for LC-MSMS analysis. Mean recoveries in spiked samples ranged from 81 to 107% with intra-day relative standard deviation (RSD) and inter-day RSD <11.2 and 9.9%, respectively. Limit of detection was determined based on signal-to-noise ratio ≥3 ranged from 0.16 to 2.11 μg kg−1 for each target. The validated protocol was successfully applied for commercial holothurian samples with a positive rate at 13.3%. And concentrations of hydroxylation metabolites were higher than reduction metabolites and precursor MEQ in positive samples. [ABSTRACT FROM AUTHOR]

In this study, a new cytochrome P450 enzyme, namely, CYP68J5_Fusarium graminearum (CYP68J5_fg), was identified from Fusarium graminearum via a combination of transcriptome sequencing and heterologous expression in Saccharomyces cerevisiae. The biotransformation of progesterone by whole-cells of S. cerevisiae expressing CYP68J5_fg revealed that the CYP68J5_fg possessed steroidal 12β- and 15α-hydroxylase activities. To the best of our knowledge, this is the first time that a fungal P450 enzyme with 12β-hydroxylase activity has been identified. This advance offers opportunities to boost the efficiency and selectivity of the CYP68J5_fg hydroxylating system and thus shows great potential for further applications of this enzyme for the synthesis of steroid drugs. IMPORTANCE Regioselective and stereoselective hydroxylation is of vital importance in the functionalization of steroids, which remains challenging in organic synthesis. In particular, the C12-hydroxy steroids play a significant role in the synthesis of many important steroidal drugs. In this study, a novel fungal P450 enzyme with 12β-hydroxylation activity was identified, and it shows different substrate specificity and regioselectivity, compared to the bacterial and fungal steroidal hydroxylases that are known to date. This lays the foundation for the creation of effective biocatalysts for the process of 12β-hydroxylation, although further understanding of the molecular structural basis of this fungal P450 is needed to facilitate the engineering of this enzyme for industrial applications. [ABSTRACT FROM AUTHOR]

Hydroxy amino acids (HAAs) are of unique value in the chemical and pharmaceutical industry with antiviral, antifungal, antibacterial, and anticancer properties. At present, the hydroxylated amino acids most studied are tryptophan, lysine, aspartic acid, leucine, proline, etc., and some of their derivatives. The hydroxylation of amino acids is inextricably linked to the catalysis of various biological enzymes, such as tryptophan hydroxylase, L-pipecolic acid trans-4-hydroxylase, lysine hydroxylase, etc. Hydroxylase conspicuously increases the variety of amino acid derivatives. For the manufacture of HAAs, the high regioselectivity biocatalytic synthesis approach is favored over chemical synthesis. Nowadays, the widely used method is to transcribe the hydroxylation pathway of various amino acids, including various catalytic enzymes, into Corynebacterium glutamicum or Escherichia coli for heterologous expression and then produce hydroxyamino acids. In this paper, we systematically reviewed the biosynthetic hydroxylation of aliphatic, heterocyclic, and aromatic amino acids and introduced the basic research and application of HAAs. [ABSTRACT FROM AUTHOR]

A highly efficient catalytic asymmetric Rubottom‐type oxidation is described. Using meta‐chloroperbenzoic acid (m‐CPBA) as the oxidant and chiral calcium phosphate as the catalyst, the facile transformation enables direct hydroxylation of N‐Boc oxindoles and β‐ketoesters in high yields (up to 99 %) and in a highly enantioenriched fashion (up to >99 % ee). The application of the established method was demonstrated by the synthesis of a pharmaceutically important 3‐hydroxyoxindole with excellent enantiocontrol. [ABSTRACT FROM AUTHOR]

Previously synthesized and spectroscopically characterized mononuclear nonheme, low-spin iron(III)-iodosylbenzene complex bearing a bidentate pyridyl-benzimidazole ligands has been investigated in alkane and aldehyde oxidation reactions. The in situ generated Fe(III) iodosylbenzene intermediate is a reactive oxidant capable of activating the benzylic C-H bond of alkane. Its electrophilic character was confirmed by using substituted benzaldehydes and a modified ligand framework containing electron-donating (Me) substituents. Furthermore, the results of kinetic isotope experiments (KIE) using deuterated substrate indicate that the C-H activation can be interpreted through a tunneling-like HAT mechanism. Based on the results of the kinetic measurements and the relatively high KIE values, we can conclude that the activation of the C-H bond mediated by iron(III)–iodosylbenzene adducts is the rate-determining step. [ABSTRACT FROM AUTHOR]

An aromatic substrate for hydroxylation by hydroxyl radicals (•OH) was investigated. The probe, N,N'-(5-nitro-1,3-phenylene)-bis-glutaramide, and its hydroxylated product do not bind either iron(III) or iron(II), and so they do not interfere with the Fenton reaction. A spectrophotometric assay based on the hydroxylation of the substrate was developed. The synthesis and purification methods of this probe from previously published methodologies were improved upon, as well as the analytical procedure for monitoring the Fenton reaction through its use, enabling univocal and sensitive •OH detection. The assay was utilised to demonstrate that the iron(III) complexes of long-chain fatty acids lack Fenton activity under biological conditions. [ABSTRACT FROM AUTHOR]