Cytotoxic activity of the seeds from Agrostemma githago var. githago

In our investigations aqueous extracts of the seeds from Agrostemma githago L. proved to be remarkably more cytotoxic in comparison with isolated agrostemmasaponins in equal concentrations. A combination of agrostemmasaponin 1 with a formyl function attached to triterpene position 4 together with agrostin, a ribosome-inactivating protein (RIP type 1; M (r): 27 kDa) which we isolated from the seed material, resulted in a markedly increased cytotoxicity. In analogy to the well-known lectin-like mechanism of action which can be inhibited by different monosaccharides, we tested seven different sugars known for their affinity to prevent cell recognition and thereby detoxify lectins. None of the tested monosaccharides diminished toxicity values significantly. This suggests that agrostin, combined with agrostemmasaponin 1, has a different mode of action to penetrate through the cell membrane than lectins. On the basis of these facts we concluded that both compounds work as a functional unity showing a mechanism of "cooperative toxicity".