Antioxidant activity and calcium binding of isomeric hydroxybenzoates

Authors

Z. Zhao
M. Vavrusova
L.H. Skibsted

Abstract

The association constant for calcium binding to hydroxybenzoates in aqueous 0.16 M NaCl at 25 °C was found electrochemically to have the value K ass = 280 mol L −1 with ΔH o = −51 kJ mol −1 , ΔS o = −122 J mol −1 K −1 for the 2-isomer (salicylate), K ass = 7 mol L −1 with ΔH o = −39 kJ mol −1 , ΔS o = −116 J mol −1 K −1 for the 3-isomer, and K ass = 8 mol L −1 with ΔH o = −51 kJ mol −1 , ΔS o = −155 J mol −1 K −1 for the 4-isomer. The 3- and 4-isomers were found more efficient as antioxidants than the 2-isomer in decreasing oxygen consumption rate in a peroxidating methyl linoleate emulsion and less sensitive to presence of calcium. All isomers were found prooxidative for iron-catalyzed initiation of oxidation due to enhanced radical formation as shown by electron spin resonance spectroscopy. Calcium salicylate was found to have low solubility with a solubility product K sp = 4.49·10 −6 based on activity with ΔH o = 67 kJ mol −1 , ΔS o = 123 J mol −1 K −1 for dissolution in water, when corrected for the strong complex formation. Calcium in food and beverages may thus lower antioxidant activity of plant phenols through complexation or by precipitation. © 2017

Abstract Image

ScienceDirect Link

10.1016/j.jfda.2017.07.001

Recommended Citation

Zhao, Z.; Vavrusova, M.; and Skibsted, L.H. (2018) "Antioxidant activity and calcium binding of isomeric hydroxybenzoates," Journal of Food and Drug Analysis: Vol. 26 : Iss. 2 , Article 51.
Available at: https://doi.org/10.1016/j.jfda.2017.07.001

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Fulltext URL

https://www.sciencedirect.com/science/article/pii/S1021949817301370/pdfft?md5=36d7095297f6f9439914ea7036eda038&pid=1-s2.0-S1021949817301370-main.pdf