Oxidation and degradation products of papaverine. Part II[1]: investigations on the photochemical degradation of papaverine solutions

The structure of the final degradation product formed in papaverine solutions in either water or chloroform was found to be a 2, 3, 9, 10-tetramethoxy-12-oxo-12H-indolo [2, 1-a] isoquinolinylium salt (a dibenzo [b, g] pyrrocolonium derivative). Its formation from papaverine oxidation products that is papaverinol, papaveraldine, and papaverine-N-oxide chloroform solutions under the influence of UV light, was investigated and possible reaction pathways are discussed.