PHOTOPHYSICAL AND PHOTOBIOLOGICAL ACTIVITIES OF A PORPHYRIN PEPTIDE FRACTION DERIVED FROM HEMOGLOBIN

In a previous study, we described the preparation of a porphyrin pepti de hydrolysate from haemoglobin, its isolation and its analysis by hig h performance liquid chromatography (HPLC) and fast atom bombardment ( FAB) mass spectrometry. The purpose of the present paper is to test th e photosensitizing activity of this fraction. We determined the single t oxygen quantum yield (Phi(Delta)) in order to quantify the efficienc y of the porphyrin peptide fraction. The quantum yield is about Phi(O- 1(2))=0.06. An analysis of the phototoxic effect on tumour cells in cu lture was performed and compared with haematoporphyrin derivative (HpD ), the only photosensitizer in clinical use at present. The phototoxic ity of the porphyrin peptide fraction is weaker than that of HpD. Howe ver, for a porphyrin dose of 50 mu g ml(-1), the difference in phototo xicity is low, and in the absence of irradiation porphyrin peptides ar e less toxic than HpD. These results suggest that porphyrin peptides c ould be potent photosensitizers; moreover, they are of great interest since they allow the solubilization of hydrophobic porphyrins and coul d be applied in the future as insoluble photosensitizer carriers.