Wildi E Langer T Schaffner W Büter KB 1998 Various locations in Switzerland were screened for Petasites hybridus plants with high petasin and low pyrrolizidine alkaloid content. The mean petasin content of the various populations ranged from 7.4 to 15.3 mg/g dry weight in rhizomes and from 3.3 to 11.4 mg/g dry weight in leaves. Mean pyrrolizidine alkaloid content in rhizomes ranged from 5 to 90 ppm whereas leaves contained between 0.02 to 1.50 ppm. These results suggest that leaves might be a preferable source for harvesting compared to the underground organ due to the finding of high petasin contents and consistently lower amounts of toxic pyrrolizidine alkaloids. https://sonar.ch/global/documents/165194 eng info:eu-repo/semantics/altIdentifier/doi/10.1055/s-2006-957422 info:eu-repo/semantics/altIdentifier/pmid/17253240 Planta medica. - 1998 Quantitative analysis of petasin and pyrrolizidine alkaloids in leaves and rhizomes of in situ grown Petasites hybridus plants. http://purl.org/coar/resource_type/c_6501