3-Ethylphenol

Chemically, wood tar is a complex mixture that contains at least 200 individual compounds, among which the foUowing have been isolated (1) 2-methoxyphenol, 2-methoxy-4-ethylphenol, 5-meth5i-2-methoxyphenol, 2,6-x5ienol, butyric acid, crotonic acid, 1-hydroxy-2-propanone, butyrolactone, 2-methyl-3-hydroxy-4JT-pyran-4-one, 2-methyl-2-propenal, methyl ethyl ketone, methyl isopropyl ketone, methyl furyl ketone, and 2-hydroxy-3-methyl-2-cyclopenten-l-one. 

Inhibition of steroid sulphatase and sulphotransferase Steroid sulphotransferase catalyses the addition of sulphate to steroidal compounds whilst steroid sulphatase catalyses the reverse reaction. In vitro studies have demonstrated that a metabolite of genistein, 4-ethylphenol, can inhibit sulphotransferase (Harris et al, 2000). Sulphoconjugates of daidzein have also been found to potently inhibit these enzymes in vitro (Wong and... 

The oxidation by strains of Pseudomonas putida of the methyl group in arenes containing a hydroxyl group in the para position is, however, carried out by a different mechanism. The initial step is dehydrogenation to a quinone methide followed by hydration (hydroxylation) to the benzyl alcohol (Hopper 1976) (Figure 3.7). The reaction with 4-ethylphenol is partially stereospecific (Mclntire et al. 1984), and the enzymes that catalyze the first two steps are flavocytochromes (Mclntire et al. 1985). The role of formal hydroxylation in the degradation of azaarenes is discussed in the section on oxidoreductases (hydroxylases). 

Hopper DJ, L Cottrell (2003) Alkylphenol biotransformations catalyzed by 4-ethylphenol methylenehydroxy-lase. Appl Environ Microbiol 69 3650-3652. 

Mclntire W, DJ Hopper, JC Craig, ET Everhart, RV Webster, MJ Causer, TP Singer (1984) Stereochemistry of l-(4 -hydroxyphenyl)ethanol produced by hydroxylation of 4-ethylphenol by / -cresol methylhydroxy-lase. Biochem J 224 617-621. 

Darby JM, DG Taylor, DJ Hopper (1987) Hydroquinone as the ring-fission substrate in the catabolism of 4-ethylphenol and 4-hydroxyacetophenone by Pseudomonas putida Dl. J Gen Microbiol 133 2137-2146. 

The degradation of 4-ethylphenol and related componnds is initiated not by oxygenation bnt by dehydrogenation to a qninone methide followed by hydroxylation (Hopper and Cottrell 2003) (Figure 8.39), and the flavocy tochrome 4-ethylphenol methylene hydroxylase in Pseudomonas putida stain JDl has been characterized (Reeve et al. 1989). 

Reeve CD, MA Carver, DJ Hopper (1989) The purification and characterization of 4-ethylphenol methylene hydroxylase, a flavocytochrome from Pseudomonas putida JDl. Biochem J 263 431-437. 

Aryl alcohol oxidase from the ligninolytic fungus Pleurotus eryngii had a strong preference for benzylic and allylic alcohols, showing activity on phenyl-substituted benzyl, cinnamyl, naphthyl and 2,4-hexadien-l-ol [103,104]. Another aryl alcohol oxidase, vanillyl alcohol oxidase (VAO) from the ascomycete Penicillium simplicissimum catalyzed the oxidation of vanillyl alcohol and the demethylation of 4-(methoxymethyl)phenol to vanillin and 4-hydro-xybenzaldehyde. In addition, VAO also catalyzed deamination of vanillyl amine to vanillin, and hydroxylation and dehydrogenation of 4-alkylphenols. For the oxidation of 4-alkylphenol, the ratio between the alcohol and alkene product depended on the length and bulkiness of the alkyl side-chain [105,106]. 4-Ethylphenol and 4-propylphenol, were mainly converted to (R)-l-(4 -hydroxyphenyl) alcohols, whereas medium-chain 4-alkylphenols such as 4-butylphenol were converted to l-(4 -hydroxyphenyl)alkenes. 

Fig. 14. Concentration profiles during the continuous indirect electrochemical oxidation of 4-ethylphenol catalyzed by the enzyme EPMH in the electrochemical enzyme membrane reactor...

The reduction of the typical smell of slurry by anaerobic digestion is the result of the breakdown of phenol, p-cresol, 4-ethylphenol, indole, skatole and the volatile fatty acids. 

The crude oil used by Bennett and Barter (1997) was a typical North Sea oil generated from Upper Jurassic, Kimmeridge clay formation source rocks. The alkylphenol distribution in a sample of (Miller) crude oil, determined using solid phase extraction (SPE), is shown in Fig. 16.21. The crude oil is dominated by phenol and cresol and contains appreciable quantities of dimethylphenols. The concentrations of 2,3-, 3,4-, and 3,5-dimethylphenol also include a contribution from 2-, 3-, and 4-ethylphenols, because they coelute under the conditions employed (Bennett et ah, 1996). 

Table 16.7 Comparisons of alkylphenol concentrations (mg/L), determined by RP-HPLC-ED after isolation by SPE of Miller oil, equilibrated oils at 25°C and 125°C, and corresponding water samples (after Bennett and Latter, 1997). Coelution of compounds determined by cochromatography with authentic standards 3,5-DMP + 4-ethylphenol 3,4-DMP + 3-ethylphenol 2,3-DMP + 2-ethylphenol Sum of concentrations in equilibrated oil and corresponding water. Reprinted from Bennett B, Latter SR (1997) Partition behaviour of alkylphenols in crude oil brine systems under subsurface conditions. Geochim Cosmochim Acta 61 4393-4402. Copyright 1997 with permission of Elsevier... 

If artificial castoreum scent marks are placed on the banks of a pond, beavers, C. canadensis, are more likely to visit, destroy, and re-mark the sites as the complexity of the artificial odor composition increases (Fig. 6.14). While some single phenolics from castoreum such as 4-ethylphenol trigger marking (Miiller-Schwarze and Houlihan, 1991), the response increases as the mixture grows to 4, 6,10,13, and finally 15 compounds. A mixture of 14 phenolics and 12 neutrals (mostly oxygenated monoterpenes) released responses almost as strong as whole castoreum (Schulte etal., 1995). 

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