Search results for "phenols"

Determination of total phenolic compounds in compost by infrared spectroscopy

2016

Abstract Middle and near infrared (MIR and NIR) were applied to determine the total phenolic compounds (TPC) content in compost samples based on models built by using partial least squares (PLS) regression. The multiplicative scatter correction, standard normal variate and first derivative were employed as spectra pretreatment, and the number of latent variable were optimized by leave-one-out cross-validation. The performance of PLS-ATR-MIR and PLS-DR-NIR models was evaluated according to root mean square error of cross validation and prediction (RMSECV and RMSEP), the coefficient of determination for prediction ( R pred 2 ) and residual predictive deviation (RPD) being obtained for this la…

Spray-dried ‘green’ polyphenols-enriched extracts from waste bentonite to produce nutraceuticals for oral care

2023

Reaction Rate Modeling in Cryoconcentrated Solutions: Alkaline Phosphatase Catalyzed DNPP Hydrolysis

2000

The hydrolysis of disodium p-nitrophenyl phosphate catalyzed by alkaline phosphatase was chosen as a model to study the kinetics of changes in frozen food products. The initial reaction rate was determined in concentrated sucrose solutions down to -24 degrees C, and the enzymatic characteristics K(M) and V(max) were calculated. The experimental data were compared to the kinetics predicted by assuming that the reaction was viscosity dependent. Indeed, an analysis of the enzymatic reaction demonstrated that both the diffusion of the substrate and the flexibility of the enzyme segments were controlled by the high viscosity of the media. When the temperature was too low for the viscosity to be …

Hydroxylation and conjugation of phenol by the frog Rana temporaria.

1985

1. Frogs injected with phenol excrete 67–95% of dose in 15h; 32–87% of dose are metabolites.2. Metabolites identified were phenyl sulphate (15–44% of dose), phenyl glucuronide (10–25% of dose), catechol sulphate (up to 7% of dose), quinol sulphate (1–25% of dose), resorcinol and catechol (traces).

Synthesis and biological evaluation of 4-nitro-substituted 1, 3-diaryltriazenes as a novel class of potent antitumor agents

2011

Abstract We describe the synthesis and biological activity of a new class of 1,3-diaryltriazenes, namely 4-nitro-substituted 1,3-diaryltriazenes. Structure–activity relationship analysis reveals that 1,3-diaryltriazenes can be modified from inactive to highly cytotoxic compounds by the introduction of two nitro groups at the para positions of benzene rings and two additional electron-withdrawing groups (bromo, chloro, trifluoromethyl or fluoro substituents) at their ortho position. In order to increase the solubility of the modified compounds, we introduced various acyl groups to their triazene nitrogen. The results of LC-MS/MS analysis showed that N -acyltriazenes can be considered as prod…

Phenolic glycosides from Phagnalon rupestre.

2002

Analysis of the butanol-soluble fraction from the methanolic extract of the aerial parts of Phagnalon rupestre (Asteraceae) has led to the isolation of seven phenolic compounds. Three have been identified on the basis of their NMR spectra as new natural compounds: the lignan 7,7'-bis-(4-hydroxy-3,5-dimethoxyphenyl)-8,8'-dihydroxymethyl-tetrahydrofuran-4-O-beta-glucopyranoside (1), the prenylhydroquinone glycoside 1-O-beta-glucopyranosyl-1,4-dihydroxy-2-(3'-hydroxy-3'-methylbutyl) benzene (2) and the acetophenone glycoside 12-O-beta-glucopyranosyl-9beta,12-dihydroxytremetone (3). The known flavonoids apigenin-7-O-beta-glucoside, luteolin-7-O-beta-glucoside, luteolin-7-O-beta-glucuronide and …

(o-Hydroxyphenyl)methylphosphonic acids: Synthesis and potentiometric determinations of their pKaValues

1993

(o-Hydroxyphenyl)methylphosphonic acids are readily obtained from o-(bromomethyl)- or o-(hydroxymethyl)phenols and trialkyl phosphites. Subsequent hydrolysis leads to the corresponding phosphonic acids. For a series of such compounds, the pKa values have been determined by potentiometry. Their dependence on additional substituents in the aromatic ring is discussed in terms of electronic and steric effects.

Compensation of steric demand by cation–π interactions, cobaltocenium cations as guests in tetraurea calix[4]arene dimers

2003

The affinities of ferrocene (2) and the cobaltocenium cation (3+), which have roughly the same size and differ in their charge, towards the inner cavity of the dimeric capsule formed by tetraurea calix[4]arene (1) were studied in C2D4Cl2 solutions. While 3+, which occupies more than 75% of the internal volume of the dimer, is readily encapsulated this is not the case for 2. This is probably due to cation-pi interactions, which operate only between 3+ and the aromatic rings of the calix[4]arene dimer. We found that the affinity of the cobaltocenium cation is higher than that of the tropylium cation (4+) and is only 2-3 times less than that of the tetraethylammoniun cation (5+). From the vari…

Syntheses, spectroscopic and structural properties of phenoxysilyl compounds : X-ray structures, FT-IR and DFT calculations

2013

Abstract The reaction of silicon disulfide with alkylphenols yields tetraphenoxysilane, cyclodisilthiane and silanethiol. The outcome of the reaction depends on the presence of the steric hindrance in the ortho position on the reacting phenol. New products of the reaction of silicon disulfide with phenols are characterized by FT-IR, NMR, X-ray diffraction and DFT calculations. The intramolecular interactions in the compounds are mainly XH---π (X = C, S) whereas the intermolecular interactions are either very weak CH---π/CH---O contacts found in aryloxysilane or electrostatic dipole–dipole attraction in cyclodisilthiane and silanethiol. The S–H---π interactions in the obtained silanethiol ar…

Bis(2,2'-biphenoxy)borates for electrochemical double-layer capacitor electrolytes.

2010

Fluorine makes the difference! Bis(2,2'-biphenoxy)borates decorated with fluorine substituents have been synthesized and studied in supercapacitor test cells (see scheme). A clear trend towards higher electrochemical stability with the increase of the fluorine content has been observed. For a maximum performance, only two fluorine substituents per benzene moiety are required.