Transfer of pyrrolizidine alkaloids from weeds to soil and medicinal plants

Nr. lzp-2022/1-0543

Pyrrolizidine alkaloids (PA) are secondary plant metabolites which are hepatotoxic in animals and humans.  The content of PA has been discovered in various products, including herbal teas, spices and herbal dietary supplements.

EC regulation 2020/2040 has set the threshold for the amount of PA present in these products. This poses challenges and constraints for aromatic plant growers. PA contamination was assumed to arise from co-harvesting PA containing weeds, however recent research has shown  that there is horizontal transfer of PA from donor plants to  soil and acceptor plants.

The research aim is to assess the transfer of PAs from the most widely distributed weeds in Latvia: field forget-me-not (Myosotis arvensis L.), small bugloss (Anchusa arvensis (L.) M. Bieb.), common bugloss (Anchusa vulgaris Dumort.), groundsel (Senecio vulgaris L.) and their residues to the soil and medicinal and aromatic (MAP) plants: chamomile (Matricaria recutita L.), peppermint (Mentha x piperita L.) and parsley (Petroselinum crispum L.). 

The most-widespread PA containing weeds in Latvia will be characterised to understand their PA composition. In the field trials accumulation of PA in soil and chamomile (Matricaria chamomilla L.) and the possibility to limit accumulation through growing technologies will be assessed.

The acquired knowledge will contribute to the improvement of food safety and will offer solutions to growers to produce medicinal plants meeting quality requirements.



  1. Determination the composition of PAs of the most widely distributed weeds in Latvia, including field forget-me-not (Myosotis arvensis ), small bugloss (Anchusa arvensis (L.) M. Bieb.), common bugloss (Anchusa vulgaris Dumort.) and groundsel (Senecio vulgaris L.).
  2. To determine if there is horizontal transfer of PAs between weeds (donor) plants and medicinal and aromatic and major crop (acceptor) plants.
  3. To determine the transfer of PAs from PA plant residues in soil to acceptor plants in field conditions.
  4. To assess the efficacy of applying of black fallow and crop-fallow to reduce contamination of soil and MAPs with PAs.
  5. To disseminate the findings and raise awareness among decision makers, the general public, consumers, and medicinal plant growers about PAs toxicity, PAs-containing plants, and potential agrotechnical methods to prevent contamination of medicinal plants on commercial fields.


  1. New knowledge on PA transfer from weeds and residues to crops and solutions to reduce transfer in arable farming.
  2. Two original scientific articles published in an internationally cited journal, indexed in the Scopus database and available open-access.
  3. Two students are involved in the research.
  4. A report prepared for policy makers.

Project duration: 1 April 2023-31 March 2026.

Lead partner: Institute for Environmental Solutions

Project scientific supervisor: Dr. Arta.Kronberga,

Project funding: the project is funded by the FLPP (Fundamental and Applied Research Projects) programme, implemented by the Latvian Council of Science

Total project budget: 299 745 EUR, among which EUR 299 745 EUR of public funding.