Interaction of tryptophan and its derivatives with oxygen- and nitrogen-centered radicals

Abstract

The interaction of tryptophan and its derivatives with the nitrogen-centered 2,2-diphenyl-1-picrylhydrazyl radical and oxygen-centered radicals formed during the radiolysis of oxygen-saturated ethanol and its aqueous solutions has been studied. It has been found that unlike pyrrole, indole, or melatonin, tryptophan, 5-hydroxytryptophan, serotonin, harman, harmine, and harmaline are capable of reducing oxygen-centered radicals by electron transfer from the lone pairs of nitrogen atoms. It has been shown that serotonin and 5-hydroxytryptophan reduce the 2,2-diphenyl-1-picrylhydrazyl radical via the transfer of hydrogen atoms from the hydroxyl groups of the molecules. In this case, pyrrole, indole, tryptophan, melatonin, harman, harmine, and harmaline, which do not contain phenolic hydroxyl groups in their structures, do not interact with the 2,2-diphenyl-1-picrylhydrazyl radical. The final molecular products of the reaction of serotonin and 5-hydroxytryptophan with 2,2-diphenyl-1-picrylhydrazyl radicals have been identified by chromatography-mass spectrometry.