@Borat Sister,
there are a boatload of different chemical types and congeners of flavinoids. Stuff like onions, parsely, apples, citrus bueberries, mushrooms, ALL have different properties and health effects.
Best ways is NOT by supplements but by natural foods because supplements can actually stimulate the metabolism of various drugs .(Kinda like grapefruit does),. Also, in eating fruits high in various flavinoids , alot of the active ingredients are along the skin and peels so dont cut up oranges hours ahead. Also, many flavinoid rich foods like onions and blueberries , can lose their chemitry in storage or cooking. (Onion is the biggest)