Phytotoxicity Assessment of Certain Phytochemical Products Containing Pyrrolizidine Alkaloids

Introduction: Tussilago farfara (coltsfoot), Petasites hybridus (common butterbur), Senecio vernalis (eastern groundsel) and Symphytum officinale (comfrey) are species traditionally used in phytotherapy that besides the therapeutic compounds contain toxic pyrrolizidine alkaloids (PAs). The aim of the paper is to determine the total PAs content and the phytotoxicity of the above species.
Material and methods: The quantitative determination of pyrrolizidine alkaloids is based on the stoichiometric reaction of protonated alkaloids with methyl orange. In acidic conditions the dye is released from the complex and its color is assessed spectrophotometrically using a linear regression curve of senecionine as a standard. The phytotoxicity was assessed by Triticum bioassay that studies the effect of the extracts (0.001–5.00%, w/v) upon root elongation (inhibitory concentration – IC50) and on the karyokinetic film.
Results: The highest amount of total PAs was found in Senecio vernalis (654.8 ± 35.96 μg/g dry plant) and the lowest in Petasites hybridus. The lowest IC50 was found for Tussilago farfara followed by Petasites hybridus, Senecio vernalis, and Symphytum officinale. The results were supported by microscopic examination.
Conclusions: The results of the spectrophotometric assay are consistent with the ones found in the literature. All extracts inhibited the elongation of the main root of wheat caryopses, however, no correlation between phytotoxicity and the PAs concentration could be emphasized.