Antioxidant Effects of Tryptanthrin Oxime

We studied the radical-binding and antioxidant activities of the alkaloid tryptanthrin (TR) and its new synthetic derivative tryptanthrin oxime (TR-Ox), as well as the cytoprotective activity of TR-Ox under conditions of oxidative stress. The antiradical activity of TR-Ox was revealed in the test of binding with stable chromogen radical 2,2-diphenyl-1-picrylhydrazyl and in the superoxide radical generation test (riboflavin photoreduction reaction with detection by NBT reduction). TR-Ox was inferior to ionol and dihydroquercetin by the antiradical activity. In these tests, TR did not exhibit antiradical activity. TR-Ox did not show iron-chelating activity (in the test with the formation of the o-phenanthroline-Fe²⁺ complex and its destruction in the presence of chelating agents). In brain homogenate, TR-Ox significantly reduced the increase in spontaneous chemiluminescence. Under conditions of oxidative stress induced by 15 mM H₂O₂ in the SH-SY5Y neuroblastoma cell culture, TR-Ox exhibited cytoprotective activity and increased the number of viable cells.