One of a group of naturally occurring phenolic compounds many of which are plant pigments. They include the anthocyanins, flavonols, and flavones. Patterns of flavonoid distribution have been used in taxonomic studies of plant species. Leguminous plants release flavonoids from their root hairs to attract nitrogen-fixing soil bacteria as a prelude to root nodule formation. Plant-derived flavonoids in foods are strong antioxidants in their natural state, but are poorly absorbed from the intestine and rapidly metabolized and excreted. However, they may be beneficial to health by modulating cell signalling pathways as well as via their antioxidant activity, and evidence suggests flavonoids may help in preventing cardiovascular disease, diabetes, and cancer. Good sources include vegetables and fruits. See also chalcone.