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The Chemical Educator
ISSN: 1430-4171 (electronic version)
Abstract Volume 29
(2024) pp 137-140
The Effect of the Antioxidant Ascorbic Acid (AA) on the Eact of Luminol-generated Free Radical Production
Charles F. Saladino,* Alexis Wyandt, and Catherine Falzone
Chemistry/Biochemistry Department, Misericordia University, Dallas, PA, csaladino@misericordia.edu
Received January 19, 2020. Accepted February 6, 2021.
Published: 27 December 2024
Abstract. It is widely accepted that free radical damage is involved in the development of numerous human pathologies. Thus, in the present study, we utilized our previously-developed chemical model system wherein a peroxide-initiated luminol reaction is used to evaluate the efficacy of antioxidants to inhibit free radical-induced chemiluminescence. The purpose of this study is to utilize this model system to evaluate the effect of the antioxidant ascorbic acid on the energy of activation of free radical production. After previously demonstrating a dose response for the inhibition of chemiluminescence at 0, 42, and 85 µM ascorbic acid, respectively, a dose response for the inhibition of chemiluminescence by ascorbic acid at temperatures of 23, 30, 37, and 42oC, respectively, was established for the baseline luminol reaction (no ascorbic acid present). These experiments were followed by a series of luminol reactions run at each of these temperatures, respectively, for concentrations of ascorbic acid of 0, 42, and 85 µM, respectively. From these data, the respective rate constants were determined, so as to allow an Arrhenius plot for the luminol reactions run with 0, 42, and 85 µM ascorbic acid, respectively. Thus, with the reactions being run in duplicate, it was determined that in the absence of ascorbic acid, the energy of activation for the luminol reaction was 41.0 joules/mole, whereas the energy of activation was 125.1 joules/mole and 163.0 joules/mole with 42 and 85 µM ascorbic acid, respectively, present in the reaction system. As expected, increasing the temperature increased the rate and amount of reaction product for each of the above reaction series. However, these data also clearly demonstrate that antioxidants increase the energy of activation of the reactions they inhibit, providing additional insight into the mechanisms by which antioxidants inhibit production of free radicals. Further, these studies provide an efficacious model for a unique biochemistry laboratory exercise.
Key Words: Laboratories and Demonstrations; biochemistry
(*) Corresponding author. (E-mail: csaladino@misericordia.edu)
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