Effect of dyes on the photodecomposition of pyridoxine and pyridoxamine

Erythrosine, eosine Y, rose bengal, mercurochrome, methylene blue, azure A and azure B accelerated the photodecomposition of pyridoxine and pyridoxamine at pH 5-9, but fluorescein and acid red did not. The photodecomposition of pyridoxine in the presence of erythrosine was greatest at pH 9.0. The singlet oxygen generated by light-excited dyes played a role as a mediator in the decomposition of pyridoxine and pyridoxamine in the presence of dyes was depressed by aminopyrine, sulpyrine and tryptophan. Pyridoxine 3,4'-dioctanoate was stable in the presence of erythrosine.