Ptesculentoside – an unfamiliar terpene glycoside from ferns

Terpene glycosides are found in a variety of plants. Ptaquiloside is one the most studied due to its carcinogenic characteristics. Severe diseases to animals occasionally ingesting bracken fern plants, like tumour development in urinary or gastrointestinal tracts, have been linked to ptaquiloside by many independently performed studies of several decades. Previous studies revealed precipitation-driven leaching of ptaquiloside from the surface of the plants to receiving water bodies¹.

The species contain more terpene glycosides than most of the plant toxin researchers recognize. Hydroxyptaquiloside analogue ptesculentoside demonstrate similar chemical reactivity and is even more water soluble than ptaquiloside. However, due to the general lack of information and absence of analytical standards and methods, the compound escapes 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.

The toxin was first elucidated in a phytochemical study by Fletcher M. T. et al in 2011² (Fig 3). It was titled under the Latin name of the subspecies of the bracken fern plant (Pteridium esculentum) wherein the amount of ptesculentoside was up to 3 times greater than of ptaquiloside. Henceforth ptesculentoside was found in biomass of the bracken fern plants in different continents of the world and is yet not known to be restricted to any particular subspecies of Pteridium.

Smiles: CC1=CC2(CC(C(=O)C2C(C13CC3)(C)O)CO)OC4C(C(C(C(O4)CO)O)O)O

References

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. Fletcher, M.T., Brock, I.J., Reichmann K.G., McKenzie R.A., Blaney B.J., “Norsesquiterpene Glycosides in Bracken Ferns (Pteridium esculentum and Pteridium aquilinum subsp. Wightianum) from Eastern Australia: Reassessed Poisoning Risk to Animals,” Agricultural and food .chemistry, vol. 59, pp. 5133-5138, 2011.

Image copyrights:

• Fig 1. PubChem
• Fig 2. Vaidotas Kisielius
• Fig 3. ResearchGate