Determination of ptaquiloside and pterosin B derived from bracken (Pteridium aquilinum) in cattle plasma, urine and milk

Ptaquiloside (PTA) is a toxin from bracken fern (Pteridium sp.) with genotoxic effects. Hydrolysis of PTA leads to the non-toxic and aromatised indanone, pterosin B (PTB). Here we present a sensitive, fast, simple and direct method, using SPE cartridges to clean and pre-concentrate PTA and PTB in plasma, urine and milk followed by LC-MS quantification. The average recovery of PTA in plasma, urine, and milk was 71, 88 and 77%, respectively, whereas recovery of PTB was 75, 82 and 63%. The method LOQ for PTA and PTB in plasma was 1.2 and 3.7 ng mL−1, 52 and 33 ng mL−1 for undiluted urine and 5.8 and 5.3 ng mL−1 for milk. The method is repeatable within and between days, with RSD values lower than 15% (PTA) and 20% (PTB). When PTA and PTB spiked samples were stored at −18 °C for 14 days both compounds remained stable. In contrast, the PTA concentration was reduced by 15% when PTA spiked plasma was left for 5 h at room temperature before SPE clean-up, whereas PTB remained stable. The method is the first to allow simultaneous quantification of PTA and PTB in biological fluids in a relevant concentration range. After intravenous administration of 0.092 mg PTA per kg bw in a heifer, the plasma concentration was more than 300 ng mL−1 PTA and declined to 9.8 ng mL−1 after 6 h, PTB was determined after 10 min at 50 ng mL−1