What class of liver-damaging plant toxins is found in ragworts and many other species?

What class of liver-damaging plant toxins is found in ragworts and many other species? The answer is pyrrolizidine alkaloids.

Pyrrolizidine alkaloids are a large class of naturally occurring plant toxins found in ragworts, groundsels, rattleweed, borage, comfrey, and other species. Many members of this chemical group are hepatotoxic, meaning they can injure the liver after ingestion.

The liver converts some pyrrolizidine alkaloids into highly reactive pyrrolic metabolites through cytochrome P450 enzymes. These metabolites can bind to DNA and proteins, producing cellular damage, mutations, and impaired liver function. A characteristic severe condition is hepatic veno-occlusive disease, now often termed sinusoidal obstruction syndrome.

Poisoning may affect grazing animals that eat ragwort or contaminated hay, as well as people exposed through herbal products, contaminated grains, honey, milk, or traditional remedies. Ragwort is therefore not merely an unpleasant weed. Cyanogenic glycosides, cardiac glycosides, and tropane alkaloids are also important plant-toxin classes, but they describe different chemical groups and toxic mechanisms.