Light-induced transformations of hematoporphyrin diacetate and hematoporphyrin

Illumination of hematoporphyrin diacetate (HP-Diac) and hematoporphyrin (HP) in phosphate-buffered solutions causes the formation of a stable photoproduct absorbing at 636 nm. Simultaneously the photo-oxidation of HP-Diac and HP takes place. These phototransformations depend on the illumination dose and the concentration of the HP-Diac or HP solution, and cause qualitatively the same spectral changes independently of the light source used.