Planta Med 2022; 88(07): 538-547
DOI: 10.1055/a-1534-6928
Natural Product Chemistry and Analytical Studies
Original Papers

Quantitative Removal of Pyrrolizidine Alkaloids from Essential Oils by the Hydrodistillation Step in Their Manufacturing Process

David S. Giera
1   G. Pohl-Boskamp GmbH & Co. KG, Hohenlockstedt, Germany
Michael Preisitsch
2   PhytoLab GmbH & Co. KG, Vestenbergsgreuth, Germany
Hugues Brevard
3   Robertet SA, Grasse, France
Jörn Nemetz
1   G. Pohl-Boskamp GmbH & Co. KG, Hohenlockstedt, Germany
› Author Affiliations


Pyrrolizidine alkaloids are naturally occurring toxins produced by certain weeds that can, if accidentally co-harvested, contaminate plant-based food, feed, and herbal medicinal products. Focusing on herbal medicinal products, the presence of pyrrolizidine alkaloids is restricted by regulatory prescribed thresholds to assure patient safety. Among the multitude of different herbal active substances utilized in herbal medicinal products, the class of pharmaceutically effective essential oils is considered to exhibit a negligible contribution to pyrrolizidine alkaloid contamination. Within the present investigation, this hypothesis should be scientifically scrutinized. For this purpose, an experimental set-up was chosen that reproduces the typical manufacturing step of hydrodistillation. Essential oils of eucalyptus and lemon were selected exemplarily and spiked with 3 representative pyrrolizidine alkaloids (retrorsine, retrorsine-N-oxide, and lycopsamine), whereupon hydrodistillation was performed. Analysis of the resulting distillates by LC-MS/MS proved that artificially added pyrrolizidine alkaloids were removed completely. Moreover, quantitative pyrrolizidine alkaloid recovery in the aqueous phases was observed. Hence, it was experimentally confirmed that herbal medicinal products employing hydrodistilled essential oils of pharmaceutical quality are intrinsically free of pyrrolizidine alkaloids due to the particularities of their manufacturing process. Furthermore, it can be concluded from theoretical considerations that essential oils produced by cold pressing have a negligible risk of carrying pyrrolizidine alkaloid contamination. Our findings provide a strong indication that the requirement for analytical pyrrolizidine alkaloid testing of essential oils for pharmaceutical use should be fundamentally reconsidered.

Supporting Information

Publication History

Received: 16 December 2020

Accepted after revision: 22 June 2021

Article published online:
22 July 2021

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