Which plant is among the most toxic and carcinogenic due to pyrrolizidine alkaloids?

• A. Fiddleneck
• B. Hound's Tongue
• C. Tansy Ragwort and Groundsel (Senecio)
• D. Comfrey

Answer: (C)

Pyrrolizidine alkaloids are a group of plant toxins that cause severe liver injury with chronic exposure. In the liver, these compounds are activated to reactive metabolites that damage hepatocytes and the tiny blood vessels, leading to progressive liver disease and, with long-term intake, an increased risk of liver tumors. The danger comes from accumulation over time, so even small amounts in forage can be hazardous to livestock and, less commonly, humans.

Among plants that contain these alkaloids, tansy ragwort and groundsel (Senecio) are especially notorious because they often have high PA content and a well-established link to severe hepatotoxicity and carcinogenic risk. The other plants listed can contain PAs as well, but Senecio is the one most consistently associated with the highest risk of chronic liver injury and cancer, which is why it is the best answer.