Using pseudophase models to determine antioxidant distributions in emulsions: why dynamic equilibrium matters

Publicada en por antiox@uvigo.es

Distributions of a homologous series of protocatechuic acid (PCA) derivatives of increasing lipophilicity were determined in stripped soybean oil-in-water emulsions and compared with their antioxidant (AO) efficiencies. The distribution was determined by employing a recently developed a kinetic method, based on the reaction between the hydrophobic 4-hexadecylbenzenediazonium ions (16-ArN2+) and the antioxidants [...]

Partitioning and antioxidative effect of protocatechuates in soybean oil emulsions: relevance of emulsifier concentration

Publicada en por antiox@uvigo.es

Distributions of a homologous series of protocatechuic acid (PCA) derivatives of increasing lipophilicity were determined in stripped soybean oil-in-water emulsions and compared with their antioxidant (AO) efficiencies. The distribution was determined by employing a recently developed a kinetic method, based on the reaction between the hydrophobic 4-hexadecylbenzenediazonium ions (16-ArN2+) [...]

Free radicals and polyphenols: The redox chemistry of neurodegenerative diseases

Publicada en por antiox@uvigo.es

The oxidation of bioorganic materials by air and, particularly, the oxidative stress involved in the cell loss and other pathologies associated with neurodegenerative diseases (NDs) are of enormous social and economic importance. NDs generally involve free radical reactions, beginning with the formation of an initiating radical by some redox, thermal or photochemical process [...]

Kinetic evidence for the formation of diazo ethers in the course of reactions between arenediazonium ions and antioxidants

Publicada en por antiox@uvigo.es

The reactions between arenediazonium ions, ArN2+, and phenolic antioxidants, AOs, are of interest because ArN2+ are involved in carcinogenic and mutagenic processes in contrast to phenolic AOs, that have biological activity and potential beneficial effects on health, and because an ArN2+ is currently being employed as a chemical probe to assess the distribution of AOs in lipid-based food emulsions [...]

Physical evidence that the variations in the efficiency of homologous series of antioxidants in emulsions are due to differences in their partitioning

Publicada en por antiox@uvigo.es

The relationships between the hydrophilic-lipophilic balance (HLB) of antioxidants (AOs) and their distributions and efficiencies in emulsions are not fully understood. Recent reports indicate that, for series of homologous antioxidants of different hydrophobicity, the variation of their efficiency with the HLB of the AO increases with the alkyl chain length up to a maximum (C3 -C8ester) followed by a decrease [...]

Optimizing the efficiency of antioxidants in emulsions by lipophilization:tuning interfacial concentrations

Publicada en por antiox@uvigo.es

Optimization of the efficiency of antioxidants, AOs, in lipid-based emulsions via chemical modifications of their reactive moieties is not always possible because of the inherent experimental difficulties and because of the regulatory status of AOs. Esterification of hydrophilic AOs may be a practical, convenient, alternative approach [...]

Interfacial Concentrations of Hydroxytyrosol and its Lipophilic Esters in Intact Olive Oil-in-Water Emulsions. Effects of Antioxidant Hydrophobicity, Surfactant Concentration and the Oil to Water Ratio on the Oxidative Stability of the Emulsions

Publicada en por antiox@uvigo.es

We determined the interfacial molarities of the antioxidants, AOs, hydroxytyrosol (HT), and HT fatty acid esters with chain lengths of 1 to 16 carbons in intact olive oil/water/Tween 20 emulsions. The results were compared with chain length effects on the oxidative stability of the same emulsions, and a direct correlation was established [...]

kinetics and mechanism of the reaction between 3-methylbenzenediazonium ions and catechol

Publicada en por antiox@uvigo.es

We have investigated the kinetics and mechanism of the reaction between 3-methylbenzenediazonium, 3MBD, ions and catechol (1,2-dihydroxybenzene, [CAT]) in aqueous buffer solution under acidic conditions by employing spectrometric UV/VIS. The variation of the observed rate constant, kobs, with the acidity at a given [CAT] follows an upward curve [...]

A physicochemical study of the effects of acidity on the distribution and antioxidant efficiency of Trolox in olive-oil in water emulsions

Publicada en por antiox@uvigo.es

The efficiency of antioxidants to inhibit the oxidation of lipid-based emulsions depends on several factors including their nature and their concentration at the reaction site. Here, we have analyzed the effects of acidity and of surfactant concentration on the distribution and efficiency of the vitamin E analog Trolox (TR) in stripped olive oil-in-water emulsions stabilized with Tween 20 [...]

Encapsulation and solubilization of antioxidants gallic acid and ethyl, propyl and butyl gallate with B-cyclodextrin

Publicada en por antiox@uvigo.es

We investigated the formation of inclusion complexes of the antioxidants (AOs) gallic acid, GA, and its hydrophobic derivatives ethyl (EG), propyl (PG) and butyl (BG) gallate with β-cyclodextrin (β-CD) by employing the UV spectral shifts method and, for the sake of comparisons, a modified phase-solubility method that exploits the use of a competitive guest molecule (acetonitrile, ACN) that completely removes the antioxidants from the CD cavity and, at the same time, keeps them in solution [...]