Cytotoxicity of heat-treated Korean mistletoe

The cytotoxic effects of preparations of Korean mistletoe (Viscum album L. var. coloratum Ohwi) on non-tumorigenic A31 cells and tumorigenic MSV cells were investigated. While the aqueous extract from Korean mistletoe (<8 μg/ml) showed strong cytotoxicity on both cell lines, the heat-treated extract was much less cytotoxic with ID50 values of above 300 μg/ml. The heat-treated extract showed a growth-enhancing effect on non-tumorigenic cells and a cytotoxic effect on tumorigenic cells. The alkaloids fraction, which was isolated from the crude extract, was not cytotoxic to non-tumorigenic A31 cells up to 550 μg/ml, but was cytotoxic to tumorigenic MSV cells at 138 μg/ml. Heat treatment did not change the cytotoxic effects of the alkaloids fraction, indicating that the selective cytotoxicity of the heat-treated mistletoe extract on tumorigenic MSV cells might be due to its alkaloids. In order to study the changes in the cytotoxicity of fermented Korean mistletoe, the crude and heat-treated extracts were inoculated with Lactobacillus plantarum. During 7 days of fermentation, the cytotoxicity of the fermented heat-treated extract was increased while that of the fermented crude extract was not changed significantly.