Dose-Dependent Selective Cytotoxicity of Extracts from Marine Green Alga, Cladophoropsis vaucheriaeformis, against Mouse Leukemia L1210 Cells.

The selective cytotoxic activity of extracts from two marine green algae, Cladophoropsis vaucheriaeformis and Halimeda discoidea, was examined via a dose response assay against mouse leukemia L1210 cells and normal NIH-3T3 cells. The MeOH-extract from C. vaucheriaeformis showed selective cytotoxicity to L1210 cells at concentrations ranging from 50 to 100 microg/ml. In particular, the greatest selectivity for cytotoxic activity was found at the concentration of 50 microg/ml, at which the growth of L1210 cells was inhibited completely and that of NIH-3T3 was not affected at all. However, MeOH extracts from the red alga Laurencia okamurae and the brown alga Dictyopteris undulata, which displayed non-selective cytotoxicity in our previous screening program, did not show similar selective cytotoxicity at any concentrations tested. These results indicate that the marine green alga C. vaucheriaeformis may contain a unique antitumor substance with selective cytotoxic activity against L1210 cells. Our results also suggest that this active substance might be of low molecular weight and therefore MeOH-soluble.