ESR9 Carina Schönsee – University of Copenhagen

NaToxAq > PhD Projects > ESR9 Carina Schönsee

ESR9 Carina Schönsee

Project: Physicochemical property determination of natural toxins

Principal supervisor: Dr. Thomas Bucheli

Intro to project:

Natural toxins are not yet commonly regarded as environmental contaminants of concern for water quality. As hardly any experimental data describing their aquatic mobility are available and in silico prediction tools show limited applicability, effective environmental risk assessment is difficult. Thus, systematic research on environmental distribution processes is urgently needed to determine whether or not natural toxins are mobile enough to end up or enrich in potential drinking water abstraction sites.

Therefore, this project aims to establish HPLC-based high-throughput methods for the systematic evaluation of model phase partitioning constants (Kow, Koc) under changing environmental conditions. Generated data will be used to validate and improve prediction models and ultimately provide first indications on those natural toxins potentially posing a threat to water quality.

Within this project, Kow values are experimentally evaluated by both indirect and direct approaches based on well-established OECD methods (OECD 117, 107) modified for application in natural toxin analysis. A multi-step calibration procedure is applied in indirect evaluation of natural toxin partition properties based on chromatographic retention. Direct analysis of partitioning behavior is performed in a miniaturized shake flask system in standard HPLC vials. As HPLC based methods, both approaches show the capability to be largely automatized for more efficient, less error-prone analysis and thus allow the reliable determination of Kow in the for potential aquatic contaminants relevant range of log Kow < 4. 

Natural toxins for analysis comprise previously investigated phytotoxins as reference compounds (e.g. colchicine from Colchicum autumnale, autumn crocus) in addition to representatives of different compound classes of phytotoxins. In regards to predicted toxicity, persistency and mobility as well as plant occurrence, specific alkaloid subclasses such as pyrrolizidine alkaloids from Senecio spp. or quinolizidine alkaloids from Lupinus spp., are investigated in more detail.

Predicted (EPISuite, ACDLabs), literature and in this project experimentally determined (each run n=3) log Kow values for the reference phytotoxin colchicine from autumn crocus (photo from Beat Bäumler – Bürenberg (BE),

As an indicator for the partitioning of natural toxins from aqueous media to organic matrices, Kow can be seen as first proxy estimating natural toxin mobility in the aquatic environment. Thus, experimental data will help in prioritization of toxins for further research activities, including field studies and lab-based characterization of fate processes within NaToxAq.

In a next step, this project will focus on systematic studies of sorption behavior of phytotoxins to model sorbents from environmentally relevant media like soils, sediments and water treatment filters. A case study will exemplify how improved physicochemical properties and experimental data in general will help predicting environmental fate of a specific group of model toxins. As a final step, generated data will be used in evaluation of commonly used prediction models.