Page 47 - FoodFocusThailand No.240 April 2026

STRONG
STRONG QC & QA QC & QA

PYRROLIZIDINE ALKALOIDS (PAs):

A HIDDEN RISK IN PLANT-DERIVED

RAW MATERIALS

Food safety is a critical public health issue that extends beyond microbial contamination to include naturally
occurring toxins that may unintentionally enter the food chain. One group of plant-derived toxins that has
gained attention is Pyrrolizidine Alkaloids (PAs), which are secondary metabolites produced by plants
as a defense mechanism against herbivores and environmental stressors. Currently, over 600 of these
compounds have been identified in nature, and they are often found in the form of N-oxide derivatives
(Pyrrolizidine Alkaloid N-oxides; PANOs).

PAs are considered important plant toxins in the context of Sources of PAs Contamination in Food
food safety because they can cause both acute and chronic PAs can be found in many plant species, particularly those
health effects in humans. High levels of exposure may result in the families Asteraceae, Boraginaceae, and Fabaceae.
in severe liver damage, while long-term, repeated exposure These compounds have also been reported in some insects
has been associated with genotoxicity and carcinogenicity. as a result of bioaccumulation from the plants they consume.
Additionally, adverse effects on the respiratory system and Contamination of PAs in the human and animal food chain
other organs have been reported. As a result, this group of often occurs unintentionally, mainly due to the mixing of
compounds is recognized as one of the natural toxins that PA-containing plants with cultivated crops during planting,
require careful monitoring within the food supply chain. harvesting, or processing of agricultural raw materials.
Foods that are frequently reported to be contaminated
Mechanism of Toxicity of PAs with PAs include tea, herbal teas, and spices, which are
Not all PAs are toxic. The most harmful are 1,2-unsaturated considered high-risk categories. This is because weeds capable
PAs, which contain a double bond between positions 1 of producing PAs, such as plants in the genera Senecio (family
and 2 of the molecular structure. These compounds are Asteraceae) and Heliotropium (family Boraginaceae), often
not directly toxic; rather, their toxicity arises only after liver grow alongside cultivated crops and may be harvested
metabolism via cytochrome P450 enzymes. This produces unintentionally. In addition, PA contamination has been found
reactive metabolites such as dehydropyrrolizidine alkaloids in honey, as bees may collect nectar and pollen from PA-
and pyrrolic esters. These reactive metabolites can interact containing plants, leading to their transfer and accumulation in
with cellular biological molecules, forming pyrrole–protein honey. Contamination may also occur in cereals and seeds
and pyrrole–DNA adducts. This leads to abnormalities in when certain plants in the genus Crotalaria (family Fabaceae)
proteins and DNA, which are a key mechanism underlying are mixed with agricultural products such as wheat, barley, or
carcinogenesis. In addition, these metabolites accumulate in maize, especially when sorting processes are not sufficiently
liver cells, damaging sinusoidal endothelial cells and causing effective. Furthermore, PAs have also been detected in herbal
hepatic sinusoidal obstruction syndrome (HSOS), which can dietary supplements.
progress to fibrosis and cirrhosis. Moreover, PA metabolites For animal products, animals that consume PA-containing
can induce oxidative stress, damaging mitochondria and plants may accumulate these compounds in their meat, milk,
cell membranes, which may ultimately lead to cell death. At or eggs. However, contamination levels in animal-derived
the same time, long-term exposure to PAs may also affect products are generally lower than those from direct plant
other organs, such as the lungs, and increase the risk of consumption, as PAs may be metabolized or diluted during
genetic mutations, which are one of the contributing factors the animal’s metabolic processes.
to cancer development.

APR 2026 FOOD FOCUS THAILAND 47

25/3/2569 BE 19:36
44-48_Strong QC&QA_�����.indd 47 25/3/2569 BE 19:36
44-48_Strong QC&QA_�����.indd 47