## 2 Natural Toxic Plant Alkaloids with Relevant Occurrence in Food
### Origin, Toxicity and Occurrence of Pyrrolizidine Alkaloids (PAs)
Therefore, the frequent intake of these alkaloids entails a potential health risk for consumers. Hence, the analytical control of PAs in food and feed it is of the utmost importance within the food safety field. PAs can enter the food chain from different vegetables and botanical sources. PA-containing plants can be directly consumed by humans (e.g., borage) and animals (e.g., forage). Nevertheless, the most common sources of PA consumption are usually plant-derived products and feed contaminated with non-edible PA-containing plants, which extensively grow as weeds in crop fields [6]. Therefore, PAs can be introduced into the food chain at early stages of the production process due to harvesting of PA-containing plants. After harvesting, it is very difficult to separate the PA-containing plant parts which produce the contamination of feed and food. Thus, to prevent PA contamination, good and very strict agricultural practices are needed to prevent harvesting the PA-containing plants or even the appearance of foreign plants in the crop [20]. This accidental PA contamination pathway was first widely assumed in an exclusive way. However, recently, different works have revealed that besides cross-contamination during harvesting processes, there are other possible contamination pathways, such as natural horizontal transfer through soil, food fraud and adulteration [6; 25; 26; 27; 28; 29; 30]. As a result, high levels of PAs have been detected in many food products: aromatic herbs and spices (65% of the food alerts notified), teas and herbal infusions (13% of the food alerts notified), plant-based food supplements (9% of the food alerts notified), herbs (6% of the food alerts notified), pollen (6% of the food alerts notified) and honey (1% of the food alerts notified) (Figure 1b) [6; 9]. Likewise, they have also been detected in other commodities, such as flour, cereals, cereal products, salads, milk, dairy products, eggs, meat and meat products, but with lower prominence [6]. As a result of the broad occurrence of PAs in a wide variety of food products and their potential health risks described above, the European Commission published in December 2020 a regulation amending Regulation (EC) No. 1881/2006 to monitor the occurrence of PAs in some food products [10]. This regulation (Commission Regulation (EU) 2020/2040) includes maximum concentration levels of PAs between 1.0 and 1000 \(\upmu\)g/kg for several products, such as: teas, herbal infusions, herbal food supplements, pollen, pollen-based food supplements, pollen products, dried herbs and cumin seeds [10]. However, this regulation does not include any product subjected to food processing. Similarly, the preparation of teas and herbal teas (transfer rate) is not considered either, since maximum limits have only been set for dried products and not for infusions (except in the case of teas and infusions for infants and young children) [10]. Therefore, new data must continue to be collected in order to include other foods in the legislation, so that dietary exposure to these contaminants can be more precisely controlled.