I read a number of years ago that Concord Grapes,Cocoa and Green Tea were high in these compounds.Here is a list from WebMD that includes some more.
Foods With Flavonoids
Many plant foods are rich in flavonoids, therefore, increasing fruits and vegetables in your diet is the easiest way to obtain them. These 10 foods are some of the best sources of dietary flavonoids available:
Berries
All berries contain flavonoids, but certain varieties are more potent than others. Blackberries are particularly powerful and include all six types of flavonoids. Blueberries, cherries, and raspberries also contain all flavonoids. Strawberries have moderate amounts of anthocyanidins.
Red Cabbage
Another great dietary source of anthocyanidins is red cabbage. Anthocyanidins, in particular, have been studied for their protective effects against cancer, cardiovascular disease, diabetes, and age-related cognitive disorders.
Onions
Onions form the basis for a multitude of cuisines, and it’s no wonder why. This humble vegetable is a powerhouse of nutrients and adds flavor to any dish. Onions are a great source of flavonols, which can reduce the risk of prostate cancer.
Kale
Another great source of flavonols is kale. Kale leaves make an excellent base for salads and can be added to soups and stews to boost their nutritional value. If you don’t care for the taste, add kale in smoothies and protein shakes to hide the taste.
Parsley
Parsley provides more flavonols in the American diet than any other food. Parsley contains over 130 milligrams of flavonols per gram. Add it to soups and sauces, or sprinkle over dishes before serving.
Tea
The easiest way to add flavonoids to your diet is to drink tea. Green, oolong, and black teas all contain high levels of flavanols, which have been studied for their benefits to cardiovascular and cognitive health.
Red Wine
Another great source of flavanols is red wine. Red wine in moderation has multiple health benefits, especially with lowering risks of cardiovascular disease.
Dark Chocolate
Chocolate and cocoa are both high in flavanols. Cocoa, in particular, has been studied for its cognitive-boosting properties and its protective effect on the cardiovascular system.
Citrus Fruits
Citrus fruits like oranges, grapefruit, tangerines, lemons, and limes contain flavanones. Juicing these fruits results in even more concentrated availability of these healthy plant compounds. You can also squeeze fresh lemon or lime juice into ice water to add nutritional value.
Soybeans
Soybeans come in a variety of different forms and are the best source of isoflavones. Eating edamame, tofu, tempeh, and soy sauce are great ways to increase isoflavones in your diet. Isoflavones have been studied for their protective effects against reproductive cancers like breast, ovarian, prostate, and testicular cancer.
No shortage here, closer to an overdose. Thanks for the info.
I’m reading this as: continue eating copious amounts of clementines, berries, cherries, and dark chocolate, for my health of course.
Also nice to see research that supports soy instead of bashing it, as someone who doesn’t eat meat but does consume a lot of soy-based products.
Like many foods, soy has a mixture of +/-.
Yeah, my friend John and I disagree on this one.
I grow and eat more than enough fruit, so I don’t pay too much mind to which one has a bit more of a particular nutrient.
I eat more vegetables than fruit but a lot of both. So I don’t worry about nutrients either. If they’re good for you, and I know they are, I’m getting enough of whatever.
The best documented intervention to slow or prevent age related memory loss is cardiovascular exercise. So moving around gardening is where it’s at! Lucky me! Of course moving to grow and eat things with flavanol couldn’t hurt it seems. Also lucky me 
I’m not getting enough vegetables. Reminds me I need to till my garden and get the green beans and summer squash in.