Enzymatic catechol derivatives

In vitro enzymatic hardening reaction of catechol derivatives bearing an unsaturated alkenyl group at 4-position of the catechol ring proceeded using laccase (PCL) as catalyst to give the crosslinked film showing excellent dynamic viscoelasticity [96],... 

On the basis of the observed products and literatures on the oxidation of phenolic conqpounds by laccase, the reaction scheme for 8-hydroxybentzon oxidation by laccase is proposed as shown in Fig.5. Initially the phenol moiety of 8-hydroxybentazon is oxidized by laccase and formed phenoxy radicals. Further reactions of these phenoxy radicals are cross coupled with each other and formed dimeric products. Ketone moiety of 8-hydroxybentazon-derived dimers are converted to enol in acidic condition. The coupling reactions most likely occur via C-C coupling at para positions because of their electronic (resonance and inductive) and satiric effects. Proposed reaction pathway leading to the formation of co-polymerization product appears to be initiated by die coupling of two catechol radicals, and subsequent oxidation of that dimmer, resulting in catechol-derived benzoquinone dimer. It appears that a tetrameric copolymerization product is formed by the non-enzymatic addition of two 8-hydroxybentazon to a catechol-derived benzoquinone dimer (Fig. 5). 

This review gives an overview of enzymatic synthesis and the properties of polymers derived from polyphenols. Catechol derivatives were enzymatically oxidized to form polymers. Urushiol analogues were designed and cured by laccase catalyst to produce artificial urushi of good elasticity. 

Enzymatically synthesized polyphenol derivatives are expected to have great potential for electronic applications. The surface resistivity of poly(p-phe-nylphenol) doped with nitrosylhexafluorophosphate was around 105 Q.4a The iodine-labeled poly(catechol) showed low electrical conductivity in the range from 10 6 to 10 9 S/cm.48 The iodine-doped thin film of poly (phenol- co- tetradecyloxyphenol) showed a conductivity of 10 2 S/cm, which was much larger than that obtained in aqueous 1,4-dioxane.24a The third-order optical nonlinearity (%3) of this film was 10 9 esu. An order of magnitude increase in the third-order nonlinear optical properties was observed in comparison with that prepared in the aqueous organic solution. 

T Matsuura, N Yoshimura, A Nishinaga, and I Saito. Photoinduced Reactions. EVIL Photosensitized Oxygenation of Catechol and Hydroquinone Derivatives Non enzymatic Models for the Enzymatic Cleavage of Phenolic Rings. Tetrahedron 28 5119-5129, 1972. 

Capsaicin and capsaicinoids undergo Phase I metabolic conversion involving both oxidative and non-oxidative paths. The liver is the major site of this enzymatic activity. Lee and Kumar (1980) demonstrated the conversion of catechol metabolites via hydroxylation of vanil-lyl ring. In rats, dihydrocapsaicin is metabolized to products that are excreted in the urine as glu-curonides (Kawada and Iwai, 1985). The generation of a quinone derivative occurs via O-demethylation at the aromatic ring with concomitant oxidation of the semiquinone and quinone derivatives or via demethylation of the phenoxy radical intermediate of capsaicin. Additionally, the alkyl side chain of capsaicin is also susceptible to oxidative deamination (Wehmeyer et al., 1990). There is evidence that capsaicinoids can undergo aliphatic oxidation (cu-oxidation) (Surh et al, 1995 Reilly et al, 2003) which is a possible detoxification pathway. Non-oxidative pathways are also involved in the bioconversion of capsaicin, e.g. hydrolysis of the acid-amide bond to yield vanillylamine and fatty acyl moieties (Kawada et al, 1984 Kawada and Iwai, 1985 Oi et al, 1992). 

All the above-mentioned glutamine-derived metabolites were found to be intermediates in the biosynthesis of the 490 quinone 438), which entails oxidation catalyzed by tyrosinase purified from extracts of A. bisporus 433). It was observed 437), however, that enzymatic oxidation of the catechol GDHB carried out at pH 6.5 produced GBQ, whereas the latter could be converted to the 490 quinone when the pH was raised to 7.8, with or without tyrosinase being present (Scheme 101). This indicated that the intramolecular transformation which provided 490 quinone in the last step was nonenzymatic. 

The first chapter by Reihmann and Ritter reviews the recent developments of peroxidase-catalyzed oxidative polymerization of phenol and derivatives with a phenolic OH group. The importance of enzymatic polymerization in general is emphasized. Properties of product polyphenols, characteristics of the enzyme catalysis, and significance of the process and the product are discussed. The second chapter by Uyama and Kobayashi is concerned with the oxidative polymerization of polyphenols, which are compounds containing more than two phenolic OH groups. These compounds include catechols and flavonoids... 

Matsuura, T, Matsushima, H., Kato, S., and Saito, 1., Photosensitized oxygenation of catechol and hydroquinone derivatives non enzymatic models for the enzymatic cleavage of phenolic rings. 

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