06 December 2019

Caudatoside – an unfamiliar terpene glycoside from ferns

Natural toxin

Hydroxyptaquiloside analogue caudatoside demonstrate similar chemical reactivity and is even more water soluble than ptaquiloside.

Fig 1. Caudatoside structure.

Terpene glycosides are found in a variety of plants. Ptaquiloside is one the most studied due to its carcinogenic properties. Proximity to bracken has been linked with increased human gastric and oesophageal cancer risk by many independently performed studies of the last several decades. The recent studies revealed precipitation-driven leaching of ptaquiloside from the surface of the plants to receiving water bodies1.

Fig 2. Pteridium aquilinum (Denmark 2017)

The species contain more terpene glycosides than most of the plant toxin researchers recognize. Hydroxyptaquiloside analogues ptesculentoside and caudatoside demonstrate similar chemical reactivity and are even more water soluble than ptaquiloside. However, due to general lack of information, the compounds escape the framework of the most prominent studies of bracken carcinogenicity. This in turn may lead to underestimation of the extent of toxicity of the plants and of risk to environmental exposure – like leaching to water reservoirs.

Within the NaToxAq network we developed a robust analytical method for simultaneous quantification of the three terpene glycosides and their degradation products, and demonstrated that the compounds can be present in plants in significantly higher concentrations than ptaquiloside2. Moreover, we found the hydrolysis product of caudatoside (pterosin A) in water, and have demonstrated for the first time the toxicity of caudatoside beyond theoretical speculations3.


  1. Clauson-Kaas, F., Ramwell, C., Hansen, H.C.B., Strobel, B.W., “Ptaquiloside from bracken in stream water at base flow and during storm events,” Water Research , vol. 106, pp. 155-162, 2016.
  2. Kisielius, V., Lindqvist, D.N., Thygesen, M.B., Rodamer, M., Hansen, H.C.B., Rasmussen, L.H. 2019. “Fast LC-MS quantification of ptesculentoside, caudatoside, ptaquiloside and corresponding pterosins in bracken ferns”. Submitted to J Chrom. B 27th September 2019.
  3. de Oliveira, L.G.S., Boabaid, F.M., Kisielius V., Rasmussen, L.H., Buroni, F., Lucas, M., Schild, C.O., López, F., da Costa, M.M., Riet-Correa, F. “Hemorrhagic diathesis in cattle due to consumption of Adiantopsis chlorophylla (Swartz) Fée (Pteridaceae)”. Submitted to Toxicon X, 28th November 2019.

Image copyrights:

  • Fig 1. PubChem
    Fig 2. Vaidotas Kisielius