Presence in Pieris rapae of Cytotoxic Activity against Human Carcinoma Cells

Cytotoxic activity in extracts of pupae and adults of various kinds of butterflies and moths was tested in vitro against the human gastric carcinoma cell line, TMK‐1, which was chosen as an example of human carcinoma cells. Among the species examined, cytotoxicity was limited to Pieris rapae, Pieris napi and Pieris brassicae. Activity was found down to a dilution of 1/10(4), while with the other butterflies and moths no activity was observed, even at 1/10(2). When the cytotoxicity of the three developmental stages, larvae, pupae and adults, of Pieris rapae was compared, the pupae showed the strongest activity, the IC(50) against TMK‐1 cells being at the 1/10(6) dilution. For larvae and adults, the respective IC(50) values were at the 1/10(5) and 5/10(5) dilutions. The active principle in the pupae of Pieris rapae was found to be heat‐labile and not extractable with organic solvents, but precipitated with ammonium sulfate and digested by proteases, suggesting that it is a protein. This cytotoxic factor was named pierisin.