What is "menthofuran"

Menthofuran is an organic compound found in a variety of essential oils including that of Pennyroyal. It is highly toxic and believed to be the primary toxin in Pennyroyal responsible for its potentially fatal effects. After ingestion of menthofuran, it is metabolically activated to chemically reactive intermediates that are hepatotoxic.

Methofuran is produced biosynthetically from pulegone by the enzyme menthofuran synthase.