More triterpenoid bisdesmosidic saponins from Agrostemma githago L. (corn cockle)

The common corn cockle (Agrostemma githago L., Caryophyllaceae) is a slender pink originally european wild-flower. Formerly widespread among wheat fields today the plant is nearly eradicated in modern agriculture and has become an endangered species that is protected by law [1]. In the past Agrostemma githago gained notoriety for its toxicity when poisoning people who consumed grain contaminated with the plant seeds [2]. This toxicity is believed to be a conserved defense mechanism based on a synergistic cytotoxicity of the contained saponins and the ribosome-inactivating protein type I (RIP-I) agrostin. Hebestreit et al. could approve this assumption. Both, the saponins as well as the RIP-I did only show little cytotoxicity when applied separately but revealed an increase in the RIP-I cytotoxicity in a synergistic manner when applied in combination in a cell culture model. Moreover Hebestreit et al. found an extraordinary high synergistic cytotoxicity when agrostin was combined with Agrostemma saponins instead of other triterpenoic saponins of similar molecular mass [3]. In 1974 Tschesche et al. and in 1998 Siepmann et al. published the structures of respectively two saponins isolated from Agrostemma githago L. [4, 5]. However other sources claim the isolation of further saponins, the accurate used species are usually not clear. We isolated four bisdesmosidic oleanane-type saponins with masses from 1527.8 g/mol to 1690.8 g/mol which partially enhanced the cytotoxicity of the RIP-I agrostin and saporin.

References:

[1] http://www.stiftung-naturschutz-hh.de/blume/2003.htm

[2] http://de.wikipedia.org/wiki/Kornrade

[3] Hebestreit, P. et al. (2006) Toxicon 47:330 – 335

[4] Tschesche, R. et al. (1974) Chem. Ber. 107:2710 – 2719

[5] Siepmann, C. et al. (1998) Planta Medica 64:159 – 164