Determination of pyrrolizidine alkaloids in tea, herbal drugs and honey

Abstract

Honey was previously considered to be one of the main food sources of human pyrrolizidine alkaloid (PA) exposure in Europe. However, comprehensive analyses of honey and tea sampled in the Berlin retail market revealed unexpected high PA amounts in teas. This study comprised the analysis of 87 honey as well as 274 tea samples including black, green, rooibos, melissa, peppermint, chamomile, fennel, nettle, and mixed herbal tea or fruit tea. Total PA concentrations in tea ranged from < LOD to 5647 µg kg⁻¹, while a mean value of about 10 µg kg⁻¹ was found in honey samples. Additionally, herbal drugs were investigated to identify the source of PA in teas. Results suggest that PA in tea samples are most likely a contamination caused by co-harvesting of PA-producing plants. In some cases such as fennel, anise or caraway, it cannot be excluded that these plants are able to produce PA themselves.

Keywords:

• pyrrolizidine alkaloids
• tea
• herbal drugs
• honey
• mass spectrometry

Acknowledgement

Special thanks to Ines Schirrmann, Corinna Genrich, Jessica Vetter, Christina Radach and Angelika Hiller for their skilful work at the laboratory. They authors also thank Professor Dr Hans Schenkel (University of Hohenheim) and his working group for the microscopic investigation of herbal drug samples.