Apples contain the flavonoid quercetin, and grapes contain catechin. Studies show that pairing the two compounds may improve cardiovascular health by making blood platelets less sticky so they don’t clump together and clog arteries. “The combination tends to have a mild anticoagulant effect,” says Barry Halliwell, PhD, nutrition professor at the National University of Singapore, who co-authored a study on quercetin and catechin. Leave the peel on the Apples, as a bulk of the antioxidants are in the peel.