Hydroxyl Radical Scavenging of Indole-3-Carbinol: A Mechanistic and Kinetic Study

Abstract

Indole-3-carbinol (I3C) is the product of the enzymatic hydrolysis of glucobrassicin in the human body. I3C exhibits diverse bioactivities. It is used as a supplement to enhance the efficiency of some cancer therapies and is available as an over-the-counter dietary supplement described as a potential antioxidant, among other health benefits. Thus, it is important to develop an in-depth understanding of its antioxidant activity. In this study, the hydroxyl radical scavenging of I3C has been investigated in silico under physiologically relevant conditions (aqueous and lipid-mimetic pentyl ethanoate environment) using thermochemical and kinetic calculations. For benchmarking purposes, the results were compared to known experimental data. The overall reaction rate constant of the HO• radical scavenging of I3C in water was found to be 2.30 × 1010 M-1 s-1 and over two times lower in lipid-mimetic pentyl ethanoate solvent at 7.74 × 109 M-1 s-1. The results also highlighted that the HO• radical scavenging follows almost exclusively the radical adduct formation mechanism (>94%) in a lipid mimetic medium, whereas this mechanism contributes about 60% in aqueous environments. I3C is considered a dopamine-like antioxidant, its main function being prevention of oxidative degradation of lipids; our study supports this view.