Control of antioxidant efficiency of chlorogenates in emulsions: modulation of antioxidant interfacial concentrations

Abstract

BACKGROUND Controlling the interfacial concentrations of antioxidants (AOs) in oil‐in‐water emulsions can be regarded as a unique approach for increasing the efficiency of AOs in inhibiting the oxidation of lipids. Classical methods to determine the AO distribution in binary systems cannot be employed and their distribution needs to be assessed in the intact emulsion. RESULTS We have employed a well‐established kinetic method to determine the distribution of a homologous series of AOs derived of chlorogenic acid in olive oil‐in‐water emulsions and analyse the effects of AO hydrophobicity on their distributions and their efficiencies. Results indicate that variations in the efficiency of chlorogenates in emulsions are due to differences in their interfacial concentrations. Their interfacial concentrations AOI were much higher (20‐ to 150‐fold) than their stoichiometric concentrations. On the other hand, their concentrations in the oil region were 1.5‐ to 0.1‐fold. Results also show the complex effect of the oil‐to‐water ratio employed in the preparation of the emulsions on the (AOI) values. CONCLUSION Results highlight the key role of the interfacial region and of its composition (interfacial AO molarity, emulsifier concentration, oil‐to‐water ratio) in interpreting the efficiency of AOs in inhibiting lipid oxidation in emulsions. Thus, a careful modulation of these parameters is necessary to ensure optimum AO efficiency. © 2019 Society of Chemical Industry

Influence of AO chain length, droplet size and oil to water ratio on the distribution and on the activity of gallates in fish oil-in-water emulsified systems: Emulsion and nanoemulsion comparison

“…In attempting to understand this non-linear trend, the distribution of a series of AOs derived from hydroxytyrosol, caffeic acid, gallic acid, protocatechuic acid and chlorogenic acid in intact olive oil, soybean oil and corn-inwater emulsions was determined by employing a pseudophase kinetic model. We demonstrated that there is a positive correlation between the efficiency of AOs and the % of AO at the interfacial region of emulsions (Almeida et al, 2016;Costa et al, 2015;Losada-Barreiro, Bravo-Díaz, Paiva-Martins, & Romsted, 2013;Losada-Barreiro, Sánchez-Paz, & Bravo-Díaz, 2013;Meireles et al, 2019;Silva, Losada-Barreiro, Paiva-Martins, & Bravo-Díaz, 2017). This fundamental result implies that the efficiency of AOs can be, in principle, increased by fine-tuning their interfacial concentrations.…”

“…This is due to the possibility to fine-tune the hydrophobicity of a polyphenol by the grafting alkyl chains of different length and should help us to understand how antioxidant properties are affected by the hydrophobicity. To date, evidence supporting using different phenolipid series such as rosmarinates (Laguerre et al, 2010), hydroxytyrosyl esters (Almeida et al, 2016;Medina, Lois, Alcántara, Lucas, & Morales, 2009), caffeates (Costa, Losada-Barreiro, Paiva-Martins, Bravo-Díaz, & Romsted, 2015) and chlorogenates (Meireles et al, 2019) in various oil-in-water emulsions has established that there is a nonlinear trend between hydrophobicity and antioxidant efficiency. Indeed, the dependence between the alkyl chain length and the antioxidant efficiency in emulsions usually follow a parabolic shape with a maximum for an intermediate alkyl length derivative (Laguerre et al, 2010(Laguerre et al, , 2011.…”

Synthesis, In Vitro Antioxidant Properties and Distribution of a New Cyanothiophene-Based Phenolic Compound in Olive Oil-In-Water Emulsions

“…This value is not necessary to describe how SIM-53B partitions between the different regions but its knowledge may be important because it delivers insights into the aspects of the reaction mechanism for the reaction between the chemical probe and SIM-53B. The k I value is comparable to that of the value obtained for chlorogenic acid ( k I = 15 mM −1 s −1 ) [ 26 ] but lower for that of, for example, gallic acid ( k I = 53 mM −1 s −1 ) [ 36 ], hydroxytyrosol ( k I = 117 mM −1 s −1 ) [ 29 ] or α-tocopherol ( k I = 190 mM −1 s −1 ) (unpublished results).…”

“…For example, at Φ I = 0.005, (SIM I ) changes from 0.17 to 0.2 M upon decreasing the O/W ratio (differences less than 15%), and the differences are much less at higher emulsifier volume fractions (Φ I = 0.045) than at lower emulsifier volume fractions (Φ I = 0.005). Therefore, changes in the oil-in-water ratio should have predictably an almost negligible effect on the antioxidant efficiency of SIM-53B in inhibiting lipid oxidation since the effectiveness of the series of homologous AOs is directly related to their distribution according to our previous work [ 25 , 26 , 27 , 28 , 29 ].…”

“…In this sense, in our previous work, we employ an innovative methodology to gain insights into the complex structure–reactivity relationships governing the efficiency of AOs in emulsions composed of different oils (soybean, olive, corn and fish) [ 22 ]. Several representative series of homologous AOs of different hydrophobicity derived from potent, natural antioxidants (gallic, chlorogenic, caffeic, protocatechuic acids and hydroxytyrosol derivatives) were employed for this purpose [ 25 , 26 , 27 , 28 , 29 ]. For the first time, it was possible to demonstrate that the effectiveness of the series of homologous of AOs is directly related to their distribution (that is, with their concentration in the interfacial region), providing new ideas for the best compression of the phenomenon of inhibition of lipid oxidation in emulsified systems and for the preparation of more effective bioactive compounds.…”