The phytochemical indole‐3‐carbinol (I3C) functions in cruciferous vegetables as a protective agent against foraging insects (Kim and Jander, 2007), and is used in humans as a dietary supplement with anti‐carcinogenic properties (Aggarwal and Ichikawa, 2005). I3C is a breakdown product of glucosinolates, which are a diverse group of small molecules produced in the Cruciferae family, including Brassica vegetables, such as broccoli and cauliflower, and also Arabidopsis thaliana.
The glucosinolates are natural components of many pungent plants such as mustard, cabbage, and horseradish. The pungency of those plants is due to mustard oils produced from glucosinolates when the plant material is chewed, cut, or otherwise damaged. These natural chemicals most likely contribute to plant defence against pests and diseases, but are also enjoyed in small amounts by humans and are believed to contribute to the health promoting properties of cruciferous vegetables.