Parent Phenol Research Articles

Retention and extractability of phenol, cresol, and dichlorophenol exposed to two surface soils in the presence of horseradish peroxidase enzyme.

The retention of phenol, o-cresol, 2,4-dichlorophenol (DCP), and their peroxidase-catalyzed polymerization products was evaluated on two surface soils. The extractability of the parent solutes and their polymerization products was also investigated. (14)C-Labeled radioisotopes were used to quantify the contaminant retained on soil as water-extractable, methanol-extractable, humic/fulvic (HA/FA) acid-bound, and soil/humin bound. Between 2 and 20% of the solute retained on soil after a 7-day contact period remained bound to the HA/FA and soil/humin components in unamended soils; in the presence of peroxidase this amount was as high as 40-75%. The alkali-extractable HA/FA component contained the largest fraction of radioactivity in peroxidase-amended soils. Whereas the soil organic matter content was the predominant factor controlling the extent of sorption of the parent phenols, the clay content and particle surface area appeared to contribute to the retention of the polymerization products. High molecular weight oligomers produced during peroxidase-mediated polymerization of phenols associate strongly with soil components and are likely incorporated into the soil organic matter via oxidative coupling reactions.

Electronic Effects on O−H Proton Dissociation Energies of Phenolic Cation Radicals: A DFT Study

The electronic effects on O-H proton dissociation energies (PDEs) of para- and meta-substituted phenolic cation radicals have been investigated by density functional theory (DFT) using B3LYP function on a 6-31G(d, p) basis set. The calculation results indicate that electron-donating groups raise the O-H PDE and electron-withdrawing groups reduce the parameter, which are opposite to the electronic effects on O-H bond dissociation energies (BDEs). In addition, the electronic effects on O-H PDE are much stronger than those on O-H BDE. The differences result from the distinct electronic effects on stabilities of phenolic cation radicals and parent phenols. The finding also implies the proton-transfer process is unlikely a rate-controlling step for phenolic antioxidants to scavenge free radicals. Moreover, like O-H BDE, O-H PDE correlate better with the resonance parameter R+ than with field/inductive parameter F. Therefore, O-H PDEs of para-substituted phenolic cation radicals are mainly governed by the resonance effect.

Phenolic Modification as an Approach to Improve the Pharmacology of the 3-Acyloxy-2-benzylpropyl Homovanillic Amides and Thioureas, a Promising Class of Vanilloid Receptor Agonists and Analgesics

In order to improve the analgesic activity and pharmacokinetics of thioureas 2 and 3, which we previously developed as potent vanilloid receptor (VR) agonists, we prepared and characterized phenolic modifications of them and of their amide surrogates (7, 8). The aminoethyl analogue of the amide template 13 was a potent analgesic with an EC50=0.96μg/kg in the AA-induced writhing test and with better in vivo stability than the parent phenol.

Comparative metabolism, covalent binding and toxicity of BHT congeners in rat liver slices

The metabolism, covalent binding and hepatotoxicity of butylated hydroxytoluene (BHT, 4-methyl-2,6-di- t-butylphenol) and two congeners (E-BHT, 4-ethyl-2,6-di- t-butylphenol; I-BHT, 4-isopropyl-2,6-di- t-butylphenol) were compared using precision-cut liver slices prepared from phenobarbital (PB)-treated male Sprague–Dawley rats. At equimolar concentrations (1 mM) BHT was the most toxic of the three compounds, causing an 80% decrease in cell viability over a 6 h incubation period. E-BHT was intermediate in toxicity while the isopropyl derivative was relatively nontoxic. Intracellular glutathione levels decreased prior to the onset of cytotoxicity. The cytochrome P450 inhibitor metyrapone completely inhibited the toxicity of all three compounds. The rates of metabolism of the three compounds to glutathione conjugates were compared in both PB-treated microsomes and PB-induced liver slices. In both models, the rate of formation was greatest for BHT, followed by E-BHT and I-BHT. Synthetic quinone methides (QMs) were prepared from each parent phenol and the rates of reactivity with three nucleophiles (water, methanol and glutathione) were compared. With each nucleophile, BHTQM was the most reactive, while I-BHTQM was the least reactive. Finally, covalent binding to protein was assessed in two ways. First, alkylation of an isolated model protein (bovine insulin) was measured in a microsomal enzyme activation system by mass spectrometry. Incubations with BHT produced the greatest extent of protein alkylation, followed by E-BHT, while no alkylation was observed with I-BHT. In the second system, covalent binding to cellular protein was assessed in rat liver PB microsomes and tissue slices by Western blotting using an antibody specific for the tert-butylphenol portion of the compounds. Binding was greatest for BHT, intermediate for E-BHT and could not be detected for I-BHT. The alkylation pattern for E-BHT was strikingly similar to that of BHT, suggesting that both compounds bound similar proteins. In summary, our results suggest that for hindered phenols such as BHT, increasing the length of the 4-alkyl substituent retards the rate of formation of reactive intermediates, significantly reduces the electrophilicity of the reactive intermediate, and greatly reduces the amount but not the selectivity of covalent binding to cellular protein, thereby reducing the toxicity of the parent compound.

Protonation of Gaseous Halogenated Phenols and Anisoles and Its Interpretation Using DFT-Based Local Reactivity Indices

The local proton affinities of phenol and its halogenated derivatives, X−C6H4−OH (X = H, F, Cl, Br, and I) in the C2 (ortho), C3 (meta), and C4 (para) ring carbon positions are determined using DFT and MO methods. Similar to the process in the parent phenol, the C4-protonation is the most preferable following a X-substitution at either the C2 or C3 position. Except for X = I, in para-X-phenols, a C2-protonation provides the most stable protonated forms; for para-I-phenol, a C4-protonation remains more favorable. At the modest B3LYP/6-31+G(d,p) + ZPE level, the proton affinities (PA's) are reasonably reproduced with a quasi systematic overestimation of about 10 kJ/mol with respect to available experimental data. The calculated PA's for X-phenols are as follows (values in kJ/mol, 2, 3, and 4 stand for the substitution positions and experimental values are given in parentheses): 2-F, 797 (788); 3-F, 813 (802); 4-F, 787 (776); 2-Cl, 801; 3-Cl, 815; 4-Cl, 789; 2-Br, 806; 3-Br, 818; 4-Br, 792; 2-I, 813; 3-I, 823; and 4-I, 816; with a probable error of ± 12 kJ/mol. A portion of the potential energy surface describing the excess proton migration over the phenol ring is elaborated. A correlation between the local PA's and the shifts of the νOH and τOH vibrational modes under protonation suggests that a resonance mechanism is likely responsible for the trend of changes in PA. Attempts to rationalize the regioselectivity of protonation are made using local reactivity indices derived from density functional theory, such as the condensed Fukui function (f) and local softness (s). While these indices could predict the preferential protonation site among C(H) atoms at various positions, which are the sites of a similar nature, they are unable to differentiate either a C- or an O-protonation or even the processes at C(H) and C(X) atoms. Proton affinities of anisole (C6H5−O−CH3) and fluoroanisoles are also evaluated (kJ/mol): anisole, 845; 2-F, 820 (exptl, 807); 3-F, 835 (826); and 4-F, 809 (796).

Identification of novel polyphenol oxidase inhibitors by enzymatic one-pot synthesis and deconvolution of combinatorial libraries.

The feasibility of enzymatic synthesis of combinatorial libraries using multifunctional starting materials [i.e., 2,4-dihydroxy-N-(2-hydroxyethyl)benzamide, 1; 4-hydroxyphenethyl alcohol, 2; 3,5-dihydroxybenzyl alcohol, 3; and 4-hydroxybenzyl alcohol, 4] with six vinyl esters, in a one-pot reaction, was investigated. Candida antarctica lipase was employed as a biocatalyst. The resulting 24-compound library contained all the expected species with no significant bias toward particular combinations of substrates. As expected, the library contained a substance(s) that showed significant inhibition of polyphenol oxidase, which was used as a model target. The deconvolution was accomplished via resynthesis of ten partial libraries, which were prepared with either an equimolar mixture of the four alcohols and a single vinyl ester, or a single alcohol and equimolar mixture of the activated esters. Analysis of the inhibition pattern observed with these partial libraries suggested that 4-hydroxybenzyl benzoate (4e) should be the most potent inhibitor. This conclusion was confirmed by the preparation and comparison of all 24 components of the initial library. Finally, it was shown that 4e was a competitive inhibitor of polyphenol oxidase, with a K(i) of 40 microM. This value compared favorably with a K(i) of 400 microM, which was determined for parent phenol 4.

Impact of peroxidase addition on the sorption-desorption behavior of phenolic contaminants in surface soils.

The impact of peroxidase addition on sorption-desorption of phenol, o-cresol, 2,4-dichlorophenol (DCP), and 1-naphthol was evaluated using two surface soils. Target chemicals were added to soils as single solutes or binary mixtures. Seven-day adsorption studies were followed by sequential fill-and-draw extractions with synthetic groundwater. Addition of horseradish peroxidase (HRP) with H2O2 was the primary treatment evaluated. HRP-mediated sorption enhancementwas related to contaminant solubility and increased in the order: naphthol < DCP < cresol < phenol. Little or no competition was observed in the presence of cosolutes. Contaminant desorption from soils was dramatically reduced upon HRP addition. Reduction in desorption was quantified using the Hysteresis Index and interpreted as attenuation of contaminant mobility. Desorption data predicted that mobility reductions followed the order: naphthol < DCP < cresol < phenol. It is believed that enzyme addition resulted in the production of hydrophobic polymers that, due to their low aqueous solubilities, readily partitioned on to the solid-phase. The adsorbed polymers were less likely to partition into the aqueous phase than the parent phenols resulting in a reduced risk to the environment.

Acid dissociation constant, a potential physicochemical factor in the inhibition of the enzyme estrone sulfatase (ES)

We report the initial results of the synthesis and biochemical evaluation of a series of aminosulfonate based compounds of phenol and the determination of the p K a of the parent phenol in an attempt to investigate the role of this physicochemical factor in the irreversible inhibition of the enzyme estrone sulfatase (ES). The results of the study show that there is a strong correlation between the observed p K a and inhibitory activity. We postulate that the stability of the phenoxide ion, as indicated by the acid dissociation constant, is an important factor in the irreversible inhibition of this enzyme.

Synthesis and antioxidative properties of novel multifunctional stabilizers

AbstractNew multifunctional stabilizers containing hindered amino, phosphite, and in some cases also free phenolic moieties have been synthesized starting from tris(diethylamino)phosphine. Some of them proved to be efficient stabilizers for model hydrocarbons and for polypropylene during processing, thermo‐, and photooxidation. Various sterically hindered phenols, amines (HAS), and phosphites have been modified by the reaction with isophorone diisocyanate (IPDI) to get new multifunctional stabilizers for polymers. The synthesized products have been investigated regarding their thermal and antioxidative behavior. The novel urethane stabilizers are, depending during the polymer processing to release the antioxidatively active parent phenols.

Hydrolysis of aryl N-methyl-N-arylsulfonylcarbamates

Tertiary sulfonylcarbamates 1 were prepared by reaction of a sulfonamide anion with aryl chloroformates. These previously unreported compounds hydrolyse in aqueous media to the parent sulfonamide and phenol. The pH–rate profile shows both spontaneous and base-catalysed processes. The reaction is also catalysed by buffers. Kinetic data for the hydrolysis of these compounds by HO− are best interpreted in terms of a mechanism involving rate-limiting formation of a tetrahedral intermediate from nucleophilic attack of hydroxide ion at the carbamate carbonyl carbon atom. For the 4-nitrophenylsulfonyl compound 1h decomposition of the tetrahedral intermediate appears to be rate-limiting with the sulfonamide anion, rather than the phenoxide, functioning as the leaving group. The buffer-catalysed process is consistent with general base-catalysed attack of water at the carbamate carbonyl carbon atom.

Novel latent initiator for cationic polymerization of epoxides

A novel latent initiator for cationic polymerization of epoxides, a composite catalyst containing aluminum complexes and phenol derivatives protected with tert-butoxycarbonyl groups (tBOC), is reported. At a certain temperature, protected phenols generate the parent phenols which are coinitiators with aluminum complexes. The deprotection temperature of the tBOC group depends on the structure of the phenol moieties. Bis(p-t-butoxycarbonyloxyphenyl)sulfone (Ph1) generates (p-dihydroxyphenyl)sulfone (PhH1) at around 150°C, the temperature at which the curing of epoxides is conventionally carried out. The thermally generated PhH1 and aluminum complexes initiate the curing of epoxides. Epoxy resin compositions containing these composite catalysts have a long shelf life at room temperature and are cured at around 150°C, showing that the composite catalyst has excellent latent properties. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 181–187, 2001

Reduction of Phenoxyl Radicals Mediated by Monodehydroascorbate Reductase

Monodehydroascorbate (MDA) reductase catalyzes the reduction of MDA, the only organic radical substrate for the enzyme reported so far. Here, we show that cucumber MDA reductase is also capable of reducing phenoxyl radicals which are generated by horseradish peroxidase (HRP) with H2O2. The addition of MDA reductase plus NADH suppressed the HRP/H2O2-dependent oxidation of quercetin, accompanied by the oxidation of NADH. The quenching of the quercetin radical by MDA reductase plus NADH was confirmed by ESR. MDA reductase with NADH also suppressed the HRP/H2O2-dependent oxidation of hydroxycinnamates, including ferulic acid, coniferyl alcohol, and chlorogenic acid. Thus, the phenoxyl radicals of plant phenols can be reduced to their respective parent phenols by MDA reductase via a mechanism similar to the reduction of MDA.

Vanadium(III) and -(IV) Complexes withO,N-Chelating Aminophenolate Ligands: Synthesis, Characterization and Activity in Ethene/Propene Copolymerization

Monoanionic, potentially bi- or terdentate aminophenolates, ([OC6H3(CH2NMe2)-2-R-4)]−, R = H (a), Me (b), tBu (c), Cl (d), N=NPh (e), MeO (f) and [OC6H2(CH2NMe2)2-2,6-Me-4]− (g)), have been used in the synthesis of well-defined vanadium-based catalysts for the polymerization of α-olefins. The reaction of [Cp2V] with the parent phenol of g resulted in oxidation of the vanadium(II) nucleus to obtain the vanadium(III) (tris)phenolate [V(OC6H2(CH2NMe2)2-2,6-Me-4)3] (1). Vanadium(III) aminophenolates could not be obtained by reaction of [VCl3(THF)3] with the sodium phenolates because of incorporation of NaCl. However, use of the corresponding silyl ether Me3SiOC6H3(CH2NMe2)-2-Me-4 (2) resulted in the formation of the chlorovanadium (bis)phenolate [VCl(OC6H3(CH2NMe2)-2-Me-4)2] (3). Attempts to oxidize 3 to the corresponding dichlorovanadium(IV) (bis)phenolate were not successful. No reaction was observed with CuCl, AgCl and PbCl2. A dark blue compound 4 was obtained with CuCl2, which was tentatively assigned as a VIII/CuII dinuclear species. Treatment of the vanadium(IV) oxo (bis)phenolates 5a−5f with SOCl2 in benzene at room temperature or in toluene at reflux temperature resulted in the formation of dark blue compounds 6a−6f, whose stoichiometries indicated excess chloride. Only when 5a and 5d were reacted with SOCl2 at −70 °C could the desired dichlorovanadium (bis)phenolates [VCl2(OC6H4(CH2NMe2)-2)2] (7a) and [VCl2(OC6H3(CH2NMe2)-2-Cl-4)2] (7d) be obtained. X-ray crystal structure determination of 1 and 3 showed that both compounds have a trigonal bipyramidal geometry with two aminophenolate ligands bound in a bidentate η2-O,N fashion to the vanadium center in similar ways. The compounds 1, 3, 6 and 7 were tested for ethene/propene copolymerization.

Synthesis, Characterization, and One-Electron Reduction of Mixed-Cyclopentadienyl/Aryloxide Titanium Dichlorides

The synthesis and characterization of a series of titanium dichloride derivatives containing both cyclopentadienyl and various substituted aryloxide ligands, [CpTi(OAr)Cl2] 10−18 and [Cp*Ti(OAr)Cl2] 19, 20, have been investigated. Compounds 10−18 are formed from the reaction of [CpTiCl3] with either 1 equiv of the substituted parent phenol in the presence of excess pyridine or with 1 equiv of the corresponding lithium salt of the substituted parent phenoxide in hydrocarbon solvents. Compounds 13, 14, 16, and 17 are chiral molecules (a nonresolved racemic pair) as a result of the presence of either ortho-(1-naphthyl) or ortho-(1-tetrahydronaphthyl) substituents on the phenoxide ligands. Titanium dichloride compounds 19 and 20 are formed in the reaction of [Cp*TiCl3] with the corresponding lithium salts of the substituted parent phenoxides in hydrocarbon solvents. The compounds 11, 13, 14, 15, 16, 18, 19, and 20 have been subjected to single-crystal X-ray diffraction analysis, and each was shown to possess a pseudo-tetrahedral geometry. The compound [CpTi(OC6H2Np-2-But2-4,6)Cl2] (16) (Np = 1-naphthyl) reacts with 1 equiv of sodium (mercury amalgam) per titanium to produce the chlorine-bridged titanium dimer [(OC6H2Np-2-But2-4,6)CpTi{μ-Cl}2TiCp(OC6H2Np-2-But2-4,6)] (21). The solid-state structure of 21 shows that the cyclopentadienyl rings are arranged in a transoid fashion about the [Ti{μ-Cl}2Ti] core with a Ti−Ti distance [3.336(1) Å] and Cl−Ti−Cl bond angles [92.07(4)°] intermediate between those found in paramagnetic [Cp2Ti{μ-Cl}2TiCp2] and diamagnetic [(ArO)2Ti{μ-Cl}2Ti(OAr)2].

Identification of novel metabolites of the xenoestrogen 4- tert-octylphenol in primary rat hepatocytes

A number of environmental pollutants, including 4- tert-alkylphenols, can mimic the actions of endogenous steroids and have the potential to disrupt the endocrine function in humans and animals. The biotransformation of a 4- tert-alkylphenol in isolated rat hepatocytes was studied in order to determine the possible fate and activity of these xenoestrogens in higher vertebrates. Hepatocytes were incubated with 30 μM 4-(1′,1′,3′,3′-tetramethylbutyl)[U- 14C]phenol (4- tert-octylphenol; t-OP) for up to 60 min. Radiolabelled metabolites were detected by radio-HPLC and the structures determined by gas chromatography–mass spectrometry (GC–MS) analysis of the conjugated or aglycone products. After a 15 min incubation, over 97% of t-OP was metabolised to a complex mixture of metabolites. The initial metabolites formed were identified as products of hydroxylation of the aromatic ring to form catechols and methylated catechols, as well as glucuronide conjugates of the catechol metabolites or parent phenol. These products were further metabolised by hydroxylation of the alkyl chain followed by glucuronide conjugation of the alkoxy group. The conjugated metabolites of t-OP are unlikely to retain estrogen receptor activity, however t-OP is metabolised by some pathways that are similar to that of estrogen catabolism, namely by ortho-hydroxylation to form catechols, methylation by catechol O-methyltransferases and ring conjugation by uridine diphosphoglucuronosyl transferases. Further investigations are needed to determine whether 4- tert-alkylphenols can alter circulating sex steroid profiles by acting as substrates of enzymes determining estrogen metabolism and excretion.

Aryloxide ligand modification: new classical catalytic systems for olefin metathesis

The AM1-calculated partial oxygen charge of several phenoxide anions, potential ligands for tungsten-based classical catalytic systems for olefin metathesis, has been used as an indication of their electronwithdrawing ability. Based on the modeled set, a number of bis(aryloxide) derivatives of tungsten (VI) oxychloride have been synthesized by refluxing the parent phenol and WOCl 4 in toluene, and we have explored their ability to catalyze various metathesis applications. The studied complexes are precursors to active metathesis catalysts when heated in the presence of Bu 4Sn, and experimental conditions for the catalysis of ring opening metathesis polymerization (ROMP), acyclic diene metathesis (ADMET) polymerization, and ring closing metathesis (RCM) are reported. The catalytic ability of the studied complexes cannot be predicted based on a single structural or electronic parameter since ligand substitution also seems to affect other features such as solubility and chemical stability of the complex. Crystal data for bis(2,4,6-tribromophenoxy)tungsten (VI) oxychloride ( 7): Space group: P 1, triclinic. a=7.8459(5) Å, α=94.100(1)°, b=8.8504(5) Å, β=92.687(1)°, c=14.2994(9) Å, γ=95.359(1)°, V=984.64(10) Å 3, R 1=0.0258 and wR 2=0.0628.

Subtype-selective N-methyl-D-aspartate receptor antagonists: synthesis and biological evaluation of 1-(heteroarylalkynyl)-4-benzylpiperidines.

4-[4-(4-Benzylpiperidin-1-yl)but-1-ynyl]phenol (8) and 4-[3-(4-benzylpiperidin-1-yl)prop-1-ynyl]phenol (9) are potent NR1A/2B receptor antagonists (IC(50) values 0.17 and 0.10 microM, respectively). Administered intraperitoneally, they both potentiated the activity of L-DOPA in the unilaterally 6-hydroxydopamine-lesioned (6-OHDA) rat, a model of Parkinson's disease. However, compound 9 was not active orally, likely due to rapid first-pass metabolism of the phenol moiety. The phenol was replaced by several bicyclic heterocyclic systems containing an NH group to function as a H-bond donor in the hope that these would be less likely to undergo rapid metabolism. In general, indoles, indazoles, benzotriazoles, indolones, and isatins gave analogues with weaker NR1A/2B activity than the parent phenols, while benzimidazolones and benzimidazolinones gave equipotent or more potent analogues. The preference for a para arrangement between the H-bond donor and the linking acetylene moiety was confirmed, and a propyne link was preferred over a butyne link. Substitution on the benzyl group or a 4-hydroxyl group on the piperidine had little effect on NR1A/2B potency; however, 4-hydroxypiperidines demonstrated slightly improved selectivity for NR1A/2B receptors versus alpha-1 adrenergic and dopamine D2 receptor affinity. From this study, 5-[3-(4-benzylpiperidin-1-yl)prop-1-ynyl]-1, 3-dihydrobenzoimidazol-2-one (46b) was identified as a very potent, selective NR1A/2B receptor antagonist (IC(50) value 0.0053 microM). After oral administration at 10 and 30 mg/kg, 46b potentiated the effects of L-DOPA in the 6-OHDA-lesioned rat and seemed to have improved oral bioavailability but lower brain penetration compared to phenol 9.

Synthesis and structure of niobium and tantalum compounds containing 2,6-diphenyl-3,5-di- tert-butylphenoxide ligation

A series of mononuclear derivatives of niobium(V) and tantalum(V) containing the new ligand 2,6-diphenyl-3,5-di-tert-butyl-phenoxide (OC 6HPh 2-2,6- tBu 2-3,5) have been isolated. The addition of the parent phenol (2 equiv. per Nb) to a benzene solution of [Nb 2Cl 10] leads to formation of the trichloride [Nb(OC 6HPh 2-2,6- tBu 2-3,5) 2Cl 3] ( 1), while treatment of the tetra-chlorides [Cp*TaCl 4] and [CpNbCl 4] with [LiOC 6HPh 2-2,6- tBu 2-3,5] leads to the mixed cyclopentadienyl, aryloxides [Cp*Ta(OC 6HPh 2-2,6- tBu 2-3,5)Cl 3] ( 2) and [CpNb(OC 6HPh 2-2,6- tBu 2-3,5)Cl 3] ( 3), respectively. Structural studies show a square pyramidal geometry for trichlorides 1– 3 with a basal aryloxide in each case. An axial aryloxide, Cp* and Cp ligand are present for 1, 2 and 3, respectively. The addition of HOC 6HPh 2-2,6- tBu 2-3,5 to the precursor [Ta(NMe 2) 5] results in formation of the mono-aryloxide [Ta(OC 6HPh 2-2,6- tBu 2-3,5)(NMe 2) 4] ( 4), which is also square pyramidal with a basal aryloxide ligand. Activation of a solution of 1 in benzene with 3 equiv. of nBuLi, followed by treatment with H 2 (1200 psi, 100°C) results in intramolecular hydrogenation of ortho-phenyl rings. Hydrolysis of the reaction mixture leads to isolation of 2,6-dicyclohexyl-3,5-di- tert-butylphenol ( 5), which has been structurally characterized.

NMR studies of tautomerism in the fungal melanin biosynthesis intermediate 1,3,8-trihydroxynaphthalene

The naphthol reductase catalysed conversion of 1,3,8-trihydroxynaphthalene (T3HN) to vermelone has been studied using a partially purified cell-free enzyme preparation from Verticillium dahliae. NMR studies show that in aqueous buffer T3HN exists as an equilibrium mixture of the parent phenol and a keto-tautomer. 1,3,6,8-Tetrahydroxynaphthalene (T4HN) is a more efficient substrate than T3HN for the naphthol reductase. 1,3-Dihydroxynaphthalene also acts as a substrate and is converted to 8-deoxyvermelone.

Toxicity of soluble products from the peroxidase-catalysed polymerization of substituted phenolic compounds

The residual toxicities of aqueous solutions of phenol and substituted phenols were investigated following polymerization under the catalytic action of soybean peroxidase (SBP) and horseradish peroxidase (HRP) enzymes. The treated mixtures obtained from the enzymatic polymerization of these phenols were usually significantly more toxic than expected, and in several cases, the residual toxicity exceeded the initial toxicity of the solution of untreated parent compound. However, this residual toxicity tended to be lower when combinations of these phenols were co-polymerized. The decrease in toxicity was attributed to the different polymeric products which form as a result of a cross-coupling between products of the enzyme-catalysed oxidation of parent phenols. The residual toxicities obtained using either SBP or HRP were not significantly different in most cases. © 2000 Society of Chemical Industry