Butylamino-demethoxy-hypocrellins and photodynamic therapy decreases human cancer in vitro and in vivo.

2-Butylamino-2-demethoxy-hypocrellin A (BAHA) and B (BAHB) are new photosensitizers synthesized by a mild reaction of hypocrellins and butylamine. In BAHA and BAHB, the peri-hydroxylated perylenequinone structure of the parent hypocrellins is preserved and the red absorption is enhanced distinctly. Electron paramagnetic resonance spin trapping measurements and 9,10-diphenylanthracene bleaching studies were used to investigate the photodynamic action of BAHA and BAHB in the presence of oxygen. Singlet oxygen (1O2) and superoxide anion radical (O2(-)) produced by illuminating BAHA and BAHB in aerobic solution have been observed. Compared with hypocrellin A and B, BAHA and BAHB primarily remained able to generate 1O2 and enhanced distinctly the O2(-)-generating abilities. The photodynamic action of BAHA and BAHB in the therapy of cancer was investigated in vitro and in vivo. Both in vitro and in vivo results revealed a significant decrease in cancer cell growth. Laser or dye alone had no effect, indicating that intratumor BAHA and laser therapy may prove useful in unresectable cancer.