Experimental and Modelling Study of Enzymatic Oxidation of 5-o-Caffeoylquinic Acid by Polyphenol Oxidases

Tarcila Bueno dos Santos¹, David Alexander Mitchell¹, Nadia Krieger², Vivian Rotuno Moure² and Éverton Fernando Zanoelo¹*

¹Federal University of Paraná, Polytechnic Center (DTQ/ST/UFPR), Graduate School of Chemical Engineering, Jardim das Américas, 81531-990, Curitiba, PR, Brazil
²Federal University of Paraná, Polytechnic Center (DTQ/ST/UFPR), Department of Chemistry, Jardim das Américas, 81531-990, Curitiba, PR, Brazil

Article history:
Received September 26, 2009
Accepted August 17, 2010

Key words:
chlorogenic acids, 5-CQA, enzymatic oxidation, polyphenol oxidases

Summary:
A set of experiments to investigate the enzymatic oxidation of 5-o-caffeoylquinic acid with polyphenol oxidases was carried out in the temperature range from 18 to 39 °C. The kinetic data were obtained in a batch isothermal reactor made of quartz and operated at an optimum pH (approx. 7.0) for enzyme activity, using citrate-phosphate buffer. The decay of 5-o-caffeoylquinic acid concentrations was experimentally monitored with a spectrophotometer at 323 nm. A coefficient of molar absorptivity equal to 1.96·10³ mM^–1m^–1 was found for 5-o-caffeoylquinic acid, based on absorbance measurements with standard aqueous solutions. The kinetic experimental results were used to calculate the parameters K_m and v_max of the Michaelis-Menten model, which were 0.24 mM and 2.77·10^–4 mM/s at 25 °C, respectively. The effects of temperature on the maximum velocity of oxidation of 5-o-caffeoylquinic acid and on the rate of enzyme deactivation were well described using the Arrhenius equation.

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