The United States Department of Agriculture has published several Special Interest Databases (SID) on flavonoids. These databases were released separately as data became available. It is anticipated that they will be combined into one database in the future.
USDA Database for the Flavonoid Content of Selected Foods. Release 3.2 (November 2015)
This database contains values for 506 food items for 5 subclasses of flavonoids: Flavonols; Flavones; Flavanones; Flavan-3-ols; Anthocyanidins.