The technical term for phytonutrients is polyphenols. They are substances produced by plants, a lot of them for self-defense. Twenty-five thousand different ones have been identified. Vitamins E, C, and beta-carotene are examples. Many of them are potent antioxidants, while some don't have antioxidant activity but boost our own antioxidant defense system. Others are involved in communication between cells, many affect gene expression, and others have detoxifying functions.