Pyrrolizidine Alkaloids from Echium vulgare in Honey Originate Primarily from Floral Nectar

Pyrrolizidine alkaloids (PAs) in honey can be a potential human health risk. So far, it has remained unclear whether PAs in honey originate from pollen or floral nectar. We obtained honey, nectar, and plant pollen from two observation sites where Echium vulgare L. was naturally abundant. The PA concentration of honey was determined by targeted analysis using a high pressure liquid chromatography mass spectrometry system (HPLC-MS/MS), allowing the quantification of six different PAs and PA-N-oxides present in E. vulgare. Echium-type PAs were detected up to 0.153 mu g/g in honey. Nectar and plant pollen were analyzed by nontargeted analysis using ultrahigh pressure liquid chromatography high resolution-mass spectrometry (UHPLC-HR-MS), allowing the detection of 10 alkaloids in small size samples. Echium-type PAs were detected between 0.3-95.1 mu g/g in nectar and 500-35000 mu g/g in plant pollen. The PA composition in nectar and plant pollen was compared to the composition in honey. Echimidine (+N-oxide) was the main alkaloid detected in honey and nectar samples, while echivulgarine (+N-oxide) was the main PA found in plant pollen. These results suggest that nectar contributes more significantly to PA contamination in honey than plant pollen.