PHOTOSENSITIZING PROPERTIES OF BACTERIOCHLOROPHYLLIN a and BACTERIOCHLORIN a, TWO DERIVATIVES OF BACTERIOCHLOROPHYLL a

Abstract

Abstract The photosensitizing properties of two water soluble derivatives of bacteriochlorophyll a , bacteriochlorophyllin a and bacteriochlorin a (lacking the central Mg‐ion) were investigated and compared to those of hematoporphyrin derivatives. At physiological pH the oxygen consumption rate of histidine, tryptophan, dithiothreitol and guanosine upon illumination was 3 to 4 times higher when bacteriochlorin a was used as photosensitizer than when hematoporphyrin derivatives were used. Especially bacteriochlorin a proved to be an effective sensitizer for the killing of L929 cells. Because bacteriochlorin a has an absorption maximum at 765 nm in phosphate buffered saline (allowing a light penetration in tissue about ten times larger than at 630 nm) and a high molar absorption coefficient (32 000 M cm −1 ) it has promising possibilities for the application in photodynamic therapy.