Pulse radiolysis studies of mangiferin:A C-glycosyl xanthone isolated from Mangifera indica

摘要

Pulse radiolysis technique has been employed to study the reaction of different oxidizing and reducing radicals with mangiferin.The reaction of ~(centre dot)OH radical showed the formation of transient species absorbing in 380-390 and 470-480 nm region.The reaction with specific one-electron oxidants (N_3~(centre dot),CCl_3O_2~(centre dot)) also showed the formation of similar transient absorption bands and is assigned to phenoxyl radicals.The pK_a values of the transient species have been determined to be 6.3 and 11.9.One-electron oxidation potential of mangiferin at pH 9 has been found to be 0.62 V vs.NHE.The reaction of e_(aq)~- showed the formation of transient species with lambda_(max) at 340 nm,which is assigned to the ketyl anion radical formed on addition of e_(aq)~- at carbonyl site.Reactions of one-electron oxidised mangiferin radicals with ascorbic acid have also been studied.