Computational Quantum Chemistry Studies of the Stabilities of Radical Intermediates Formed During the Oxidation of Melatonin

• Main Author: Warden, Constance E
• Format: Others
• Language: English
• Published: Digital Commons @ East Tennessee State University 2016
• Subjects: Melatonin; Free Radical; Spin Trap; Basis Set Extrapolation; HF; MP2; DFT; Physical Chemistry
• Online Access: https://dc.etsu.edu/etd/3135; https://dc.etsu.edu/cgi/viewcontent.cgi?article=4541&context=etd

Melatonin, a nontoxic natural antioxidant, is of interest as a possible spin trap for use in spectroscopic methods to observe and identify short-lived free radicals, which have been linked to oxidative stress that may result in serious health problems. However, the reaction mechanisms for the oxidation of melatonin to form the product N1-acetyl-N2-formyl-5-methoxykynuramine are still not well understood. Computational quantum chemistry studies have been done on four proposed reaction mechanisms, involving the following major intermediate structures: a dioxetane, an epoxide, a melatonin radical cation, and a spin radical adduct. Molecular geometries were optimized at the DFT/B3LYP/cc-pVTZ level of theory, and single point energies were extrapolated to the complete basis set limit at the Hartree-Fock and second-order Møller-Plesset perturbation levels of theory using the cc-pVXZ (X = D, T, Q) basis sets. The lowest energy pathway was found to be the single electron transfer pathway, involving the melatonin radical cation intermediate.