Pyrrolizidine Alkaloids in Food: Analytical, Toxicological and Health Considerations

Abstract

Pyrrolizidine alkaloids (PAs) are a large group of natural toxins produced by plants, several of which are known to be highly hepatotoxic and also have been shown to be carcinogenic. PAs have been associated with a number of livestock diseases and cases of human poisoning following contamination of staple foods, generally grain crops, or upon consumption of some herbal remedies. Other possible food sources of exposure include honey, milk, offal and eggs, which have all been found to contain PAs, although cases of human poisoning resulting from exposure through these sources have not been reported. It is unknown whether PA residues are present in meat, but the potential for exposure is thought to be slight due to the fast metabolism and elimination of PAs from the bodies of animals. Veno-occlusive disease is the most prominent hepatic lesion resulting from PA poisoning. Classical symptoms and signs are abdominal pain and rapidly developing ascites. The effects of PAs can take time to develop and might result from long-term low-level exposure. Cases of poisoning in humans and livestock, combined with the results of studies in experimental animals indicate that there is variation between species in susceptibility to PAs. Highly toxic PAs are generally macrocyclic diesters of retronecine. The extent of toxicity depends not only upon the molecular structure but also upon the mechanism of exposure, some of which are yet to be fully elucidated. Currently, there are no European Union regulatory limits for PAs and their N-oxides. The guideline regulation recommended by the European Food Safety Authority is not to exceed an intake of 0.007 μg kg−1 body weight day−1 of 1,2-unsaturated PAs as doses at this level are unlikely to pose a risk of cancer. This review also covers the range of biological and chemical methods that have been applied for both the qualitative and quantitative detection of PAs and PANOs in food (grain, honey, milk, cheese, teas), animal feed and traditional Chinese medicines.