Evaluation of tetraphenyl-2,3-dihydroxychlorins as potential photosensitizers

A series of β,β-dihydroxychlorins derived from meso-tetraphenylporphyrins (TPPs) have been synthesized. Their in vitro cytotoxicity has been measured and compared to BPDMA (verteporfin). Under the assay conditions BPDMA had an LD 50 (lethal dose to kill 50% of cells) value of 0.007 μM (5 ng/mL). The LD 50 values for the TPP derivatives varied from 1.7 × 10 -2 to 9.9 μM depending upon the substituents and their position on the phenyl groups. One example of the dihydroxychlorin prepared from unsubstituted 5,15-diphenylporphyrin was examined and this exhibited an LD 50 of 2.4 × 10 -3 μ M !