Pyrrolizidine alkaloids (PAs) are a group of naturally occurring alkaloids based on the structure of pyrrolizidine. PAs are produced by plants as a defense mechanism against insect herbivores. Due to their potential detrimental health effects, pyrrolizidine alkaloids (PA) must be avoided in food and beverages.
PA in Tea and Herbal Infusions
The German Federal Institute for Risk Assessment (BfR) raised concern on the occurrence of pyrrolizidine alkaloids (PAs) in teas and herbal infusions on the market in 2013. In response the UE has implemented a testing method for 28 PA substances and has been checking all raw materials on PA. Traces of PA in tea and herbal raw materials were detected, indicating a contamination by foreign plant components. By now there is solid proof that crops can be contaminated with pyrrolizidine-producing weeds, and the alkaloids find their way into the finished product.
The following 28 PA substances are currently checked for:
Echimidin, echimidin-N-oxide, erucifolin, erucifolin-N-oxide, europin, europin N-oxide, heliotrin, heliotrin N-oxide, intermedin, intermedin N-oxide, jacobin, jacobin-N-oxide, lasiocarpin, lasiocarpin N-oxide, lycopsamin, lycopsamin N-oxide, monocrotalin, monocrotalin N-oxide, retrorsin, retrorsin N-oxide, senecionin, senecionin N-oxide, seneciphyllin, seneciphyllin N-oxide, senecivernin, senecivernin-N-oxide, senkirkin, trichodesmin.
Health effects: Pyrrolizidine alkaloids are reported to be hepatotoxic, that is, damaging to the liver. They are also supposed to be tumorigenic and can cause hepatic veno- occlusive disease and liver cancer. Hence, the consumer expects a zero tolerance regarding PA in tea and infusion products.
Source of Pyrrolizidine Alkaloids
Pyrrolizidine alkaloids are primarily found in the following plant families:
1. Asteracea family (Compositae): in plants of the Senecioneae subtribe (the genus Senecio is prevalent) and the Eupatorieae subtribe (mainly in the genera Eupatorium and Ageratum).
2. Boraginaceae family: in virtually all plants of this family (e.g. borage and comfrey)
3. Fabaceae family (Leguminosae): in the subtribe Crotalariaceae, mainly in the genus Crotalaria, but also in the genera Chromolaena and Lotononis.
How to avoid PA Contamination
Prevention of exposure remains the only effective method of limiting toxicity due to PAs. As foreign plants are the major source of PA contamination in herbal raw material and tea, utmost care has to be taken in order to establish and keep fields and plantations and their surroundings clean and control weed growth. The following measures need to be implemented:
toxic PA-containing flora growing in the region, particularly those that may or do grow along the respective crop should be identified;
all suspected plant species should be checked for their PA content in specialized laboratories;
appropriate agro-technical practices should be followed for the prevention/control of PA-containing plants in crop fields and plantations. Aside from the use of herbicides, manual weeding shall be considered to minimize occurrence of critical weeds plants;
viable systems shall be developed for the routine inspection of fields prior to harvest to detect the presence of PA-containing plants;
if the crop is found to be contaminated, immediate steps must be taken to remove the toxic plants from the fields at two critical stages: prior to flowering and again, prior to the harvest.
Please note: the presence of only 10 toxic plants (such as Senecio) per hectare can lead to a critical contamination of a raw material lot! Please also take note that all plant parts contain PA, including seeds.
All persons involved in the harvesting of wild plants must ensure that only the desired plant is collected. In the course of collection, care must be taken to ensure that no foreign plants or toxic weeds can mix with the harvested crop and confusion (due to ignorance or bad faith) in the collection of different species is avoided.
Training & education:
All persons involved in the cultivation, collection, and handling of raw materials shall be properly informed and systematically trained regarding the importance of avoiding PA contamination and the above mentioned measures. Training material such as visual hand- out for weeding crews and / or collectors shall be developed.