Toxicity mechanism, pyrrolizidine

Whilst the N-oxidation of pyrrolizidine alkaloids is a recognized detoxifying mechanism in mammals [26], it has also been shown that ingested N-oxides are indeed toxic, presumably via in vivo reduction to the parent pyrrolizidine alkaloids... 

Mattocks, A. R. Mechanisms of pyrrolizidine alkaloid toxicity. "Proc. 5th Int. Congr. Pharmacology", vol. 2 S. Karger Basel, 1973 p. 114-123. 

H. Hepatic failure. A variety of dmgs and toxins may cause hepatic injury (Table 1-29). Mechanisms of toxicity include direct hepatocellular damage (eg. Amanita phalloides mushrooms [see p 273]), metabolic creation of a hepato-toxic intermediate (eg, acetaminophen [p 66] or carbon tetrachloride [p 154]), or hepatic vein thrombosis (eg, pyrrolizidine alkaloids see Plants, p 309). 

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