Coexistence of Substituted Phenols Reduces the Fouling Ability of Phenol in Non-aqueous Solvents

The electrooxidation of phenol showed different rate of deactivation by varying the concentration of substituted phenols (4-chlorophenol, 4-methoxyphenol, 4-tert-butylphenol). This was due to the more favourable solubility properties of the product copolymers compared with poly(phenyleneoxide) the product which forms when only unsubstituted phenol is present. The nature of substituent, switching potential and oxidation potentials of the studied phenols were significant in prevention of electrode fouling. The best reproducibility could be achived upon addition of 4-chlorophenol. This offered a possibility for estimation of phenol concentration in non-aqueous systems.

An efficient bifunctional ionic liquid [BIL] as solvent and catalyst system for O-alkylation of phenols under solvent-free condition- An environmental benign approach

: Bifunctional ionic liquid [BIL] was found to be a highly effective catalyst for the ether synthesis without any inorganic base or solvent. By this protocol, different aryl substitutions were reacted with different phenol in good to excellent yields. The BIL is reusable without any loss in catalytic activity for nine consecutive cycles. Background: The Williamson reaction is a convenient renovation in fine chemical synthesis since the ethers are important in both bulk and fine industrial chemicals preparation and academic applications. Objective: The aim of this study is to highlight the use of BIL to synthesize mixed ethers using substituted phenols and to study the reusability in the next cycle. Method: The mixture of the phenol (1mmol), alcohol (1.2 mmol) and BIL ionic liquid (0.3 mol%) was added in to round-bottomed flask (100 mL) with continuous stirring for 1 hour. Results: The products obtained were phenol and substituted phenols containing withdrawing substituents in respectable yields. However, the reactions involving substituted phenols containing electron-donating groups often afford the corresponding products in low yields. Conclusion: BIL is found to be an effective catalyst in the etherification of various unsymmetrical ethers under mild conditions. Bifunctional ionic liquid as a solvent and catalyst will show real rewards by providing a ‘green’ method with the safer procedure, less reaction time periods, mild conditions, separation easy, and ionic liquid recycle.

The Oxidation of Equol by Tyrosinase Produces a Unique Di-ortho-Quinone: Possible Implications for Melanocyte Toxicity

Equol (7-hydroxy-3-(4′-hydroxyphenyl)-chroman, EQ), one of the major intestinally derived metabolites of daidzein, the principal isoflavane found in soybeans and most soy foods, has recently attracted increased interest as a health-beneficial compound for estrogen-dependent diseases. However, based on its structure with two p-substituted phenols, this study aimed to examine whether EQ is a substrate for tyrosinase and whether it produces o-quinone metabolites that are highly cytotoxic to melanocyte. First, the tyrosinase-catalyzed oxidation of EQ was performed, which yielded three EQ-quinones. They were identified after being reduced to their corresponding catechols with NaBH4 or L-ascorbic acid. The binding of the EQ-quinones to N-acetyl-L-cysteine (NAC), glutathione (GSH), and bovine serum albumin via their cysteine residues was then examined. NAC and GSH afforded two mono-adducts and one di-adduct, which were identified by NMR and MS analysis. It was also found that EQ was oxidized to EQ-di-quinone in cells expressing human tyrosinase. Finally, it was confirmed that the EQ-oligomer, the EQ oxidation product, exerted potent pro-oxidant activity by oxidizing GSH to the oxidized GSSG and concomitantly producing H2O2. These results suggest that EQ-quinones could be cytotoxic to melanocytes due to their binding to cellular proteins.

Co-metabolic biodegradation of 4-bromophenol in mixture of pollutants system by Arthrobacter chlorophenolicus A6

Brominated phenols are listed as priority pollutants, and are the key components of paper pulp wastewater together with nitrophenol and chlorophenol. However, the biodegradation of bromophenol in a mixed substrate system is very scanty. In the present investigation, simultaneous biodegradation kinetics of three substituted phenols (4-bromophenol, 4-BP; 4-nitrophenol, 4-NP; and 4-chlorophenol, 4-CP) were investigated using Arthrobacter chlorophenolicus A6. A 23 full factorial design was applied with varying 4-BP and 4-CP from 75–125 mgl− 1and4-NP from 50–100 mgl− 1. Almost complete degradation of this mixture of substituted phenols was achieved at an initial concentration combination of 125, 125, and 100 mgl− 1of 4-CP, 4-BP, and 4-NP, respectively in 68 h. Statistical analysis of the results revealed that among the three variables, 4-NP had the most prominent influence on both degradations of 4-CP and 4-BP. While the concentration of 4-CP had a strong negative interaction effect on the biodegradation of 4-NP. Irrespective of the concentration levels of these three substrates, 4-NP was preferentially biodegraded over 4-CP and 4-BP. Further, 4-BP biodegradation rates were found to be higher than that of 4-CP followed by 4-NP. Besides, the variation of biomass yield coefficient of the culture was investigated at different initial concentration combinations of these substituted phenols. Although the actinomycetes consumed 4-NP at a faster rate, the biomass yield was very poor. This revealed that the microbial cells were more stressed when grown on 4-NP compared to 4-BP and 4-CP. Overall, this study revealed the prospective of A. chlorophenolicus A6 for the degradation of 4-BP in mixed substrate systems.