ESR7 Vaidotas Kisielius

Project: Spatial and temporal variation in the production and release of glycosidic natural toxins in nonagricultural terrestrials

Principal supervisor: Dr. Lars Holm Rasmussen

Intro to project:

The chemicals of this project are focused to glycosidic toxic compounds naturally occurring in nonagricultural ecosystems. This is a very diverse group of substances acting in plants as built-in insect repellents and grazing deterrents. The molecular structures of glycosides make them highly water soluble and mobile in soils and sediments. On several occasions this group of toxins has been identified in soil and water environments. Their general adverse effects such as acute toxicity to aquatic organisms are also commonly recognised.

The natural abundance, mobility and toxicity of the glycosidic toxins make them excellent candidates for tracing and collecting, gathering relevant data, performing thorough analysis and putting forward the relevant arguments to support or oppose the hypothesis that naturally appearing biological toxins inhibit the quality of the drinking water supplies.

A method for isolation of 3 glycosidic natural toxins – ptaquiloside, ptesculentoside, caudatoside and their hydrolysis products – pterosins B, G and A has been developed. The compounds were isolated from the bracken fern plants (Pteridium esculentum). Their molecular identities confirmed by mass spectrometry and concentrations determined applying purity measurements by nuclear magnetic resonance. UV absorbance profiles of the novel compounds were obtained.

A fast analytical LC-MS method for simultaneous quantification of the 6 abovementioned compounds in the bracken fern plants has been developed and validated individually for each compound and an internal standard in terms of linearity, limits of detection (LOD), limits of quantification (LOQ), recovery and precision. Analytical standards and details of the analytical method were distributed within the NaToxAq network.

Over 200 samples of Pteridium aquilinum and Pteridium latiusculum were taken in a continual 1500 km cross-sectional area of Denmark, Sweden and Finland and in a random geographical locations in the United Kingdom and Lithuania. The samples were taken predominantly considering their proximity to surface and ground water resources. Additional samples of Pteridium species were taken in Denmark over a 6 month vegetation season of 2018 and preserved for the studies of temporal variation of the compounds (84 samples).

Methods of extraction and preconcentration of the compounds from analytical samples were optimised and occasional samples were analysed with the developed analytical method showing the amount of ptaquiloside, ptesculentoside and caudatoside in the biomass of Danish origin Pteridium aquilinum of up to 3,0; 0,3 and 0,5 mg/g DW respectfully. 

The developed analytical method and standards will be used to analyse the collected samples of biomass and publish the work Spatial and temporal variation of Ptaquiloside-like compounds in the biomass of Bracken fern plants and imposed risks to surface water quality. Determination of possible trends of the concentrations of the compounds in relation to the geographical location, climate, season, access to sunshine, co-growing species, etc. will be made.

The analytical method will be adjusted and validated for direct quantification of the compounds in surface waters. Water samples will be taken in regions that will be determined as highly infested with the compounds by the previous study. Environmental precursors causing compounds to occur in water will be illustrated and published in a scientific article dedicated for leaching of the compounds. Besides Pteridium, the PhD project attempts to exploit the existing analytical methods to study pyrrolizidine alkaloids in water resources, leaching from species of Petasites.