The most prominent horsetail species, Equisetum arvense, has an array of different medicinal properties, thus the proper authentication and differentiation of the plant from the more toxic Equisetum palustre is important. This study sought to identify different samples of E. arvense and E. palustre using three analytical methods. The first method involved the use of HPTLC analysis, as proposed by the European Pharmacopoeia. The second, HPLC-ESI-MS/MS, is capable of both identification and quantification and was used to determine the Equisetum alkaloid content in each sample. A third method was DNA barcoding, which identifies the samples based on their genetic make-up. Both HPTLC and HPLC-ESI-MS/MS proved to be suitable methods of identification, with HPLC-ESI-MS/MS proving the more sophisticated method for the quantification of alkaloids in the Equisetum samples and for determining the adulteration of E. arvense. For DNA barcoding, optimal primer pairs were elucidated to allow for the combined use of the rbcL and ITS markers to accurately identify each species. As new DNA marker sequences were added to GenBank, the reference library has been enriched for future work with these horsetail species.

The current expansion of Equisetum palustre in wetlands across the Northern Hemisphere has led to an increase in reports of adverse effects in livestock. In light of the limited reduction potential of toxic Equisetum alkaloids through feed conservation measures, it is essential to identify effective strategies to manage E. palustre infested biomass. This study examined the impact and efficacy of biomethanization processes on the biodegradation of Equisetum alkaloids. To monitor the biodegradation in such complex matrices, a sample preparation method and a high-performance liquid chromatography electrospray ionization mass spectrometry (HPLC-ESI-MS/MS) method were established. The developed method was successfully employed to quantify the total residual content of Equisetum alkaloids in fermentation residues following biomethanization in batch experiments. It was demonstrated that under such conditions a degradation greater than 95 % was achieved. The biomethanization process described here is currently the most effective biological treatment for reducing Equisetum alkaloids. It is notable that the methane yields remained largely unaffected, indicating that field cuttings contaminated with E. palustre can be safely and economically processed via biomethanization which would be a key prerequisite for a circular bioeconomy.