Phytochemical: The active health-protecting compounds that are found as components of plants.

Currently, the terms "phytochemical" and "phytonutrient" are being used interchangeably to describe those plant compounds which are thought to have health-protecting qualities.

The antioxidant, immune boosting and other health promoting properties of active compounds in plants are being investigated. Phytonutrients or phytochemicals that are being studied presently include (and are not limited to) terpenes, carotenoids, limonoids, and phytosterols.