Porphyrin-Induced Photogeneration of Hydrogen Peroxide Determined Using the Luminol Chemiluminescence Method in Aqueous Solution: A Structure-Activity Relationship Study Related to the Aggregation of Porphyrin

Abstract

A luminol chemiluminescence method was used to evaluate the porphyrin-induced photogeneration of hydrogen peroxide (H₂O₂). This method enabled us to detect H₂O₂ in the presence of a high concentration of porphyrin, which was not possible using conventional colorimetry. The limit of detection was about 1 µM. We compared the ability to generate H₂O₂, using uroporphyrin (UP), hexacarboxylporphyrin (HCP), coproporphyrin (CP), hematoporphyrin (HP), mesoporphyrin (MP), and protoporphyrin (PP). The amount of H₂O₂ photoproduced was strongly related to the state of the porphyrin in the aqueous solution. UP and HCP, which existed predominantly in a monomeric form, had a good ability to produce H₂O₂. HP and MP, existing as dimers, showed weak activity. CP, forming a mixture of monomer and dimer, had a moderate ability to produce H₂O₂. PP, which was highly aggregated, had a good ability. These results demonstrated that the efficiency of porphyrins to produce H₂O₂ was strongly dependent on their aggregated form, and the dimer suppressed the production of H₂O₂.