An in vitro study on the kinetics, subcellular distribution and phototoxicity of harmine in human tumor cells.

The beta-carboline alkaloid harmine, which was found to possess interesting phototoxic properties in different biological systems, was investigated for photokilling of human tumor cells in vitro. Harmine was readily accumulated by HeLa cells, localized preferably in cytoplasm, being a non toxic compound when used at low concentrations. The photoactivation of harmine-loaded cells with UV radiation showed lysosomal damage, reflected by altered localization of the fluorescent probe acridine orange, as well as an evident cell killing which increase with time up to a maximal value 48 h after the photodynamic treatment.

Simple beta-carboline alkaloids as nucleic acids fluorochromes.

Treatment of cell smears (chicken blood, Trypanosoma cruzi epimastigotes, Ehrlich ascites tumor cells and mouse spleen) with simple beta-carboline alkaloids induced a strong bluish white fluorescence emission of condensed chromatin and basophilic cytoplasm under ultraviolet excitation. The compounds used were harmine, harmol, harman, norharman, harmalol and harmaline (25-50 micrograms/ml aqueous solutions for 2-3 min). Spectrofluorometric studies on harmine solutions in vitro (emission peak at 420 nm) showed fluorescence quenching at high concentrations as well as in the presence of DNA. Microscopic fluorescence features of these new fluorochromes and possible binding modes to nucleic acids are discussed.