Well, the term flavonoid antioxidant is a bit confusing because a antioxidant describes the one of the purposes of the flavonoid. I guess it would be like saying “what is a car parking?” The answer to that would be parking is one of the things a car does.
Polyphenols are the type of antioxidants found in plants and in red wine. Of these polyphenols there are two types: flavonoids and nonflavonoids.
Flavonoids have become more important since discoveries that concluded flavonoids have healthy benefits to humans, specificaly antiviral, anti-allergic, antiplatlet, anti-inflammatory, antitumor and antioxidant activities.
Flavonoids protect against these and other diseases because they add to the overall antioxidant part of the immune system. There are over 4,000 identified flavonids which are all characterized by their chemical structure. Depending on their structure, they could fall into one of these types: flavonols, flavonies, flavanoies, isoflavones, catechins, anthocyanidins and chalcones.
A flavonoid antioxidant is found in plants like oranges, grape juice, apples, onions, tea and cocoa. While Vitamins A, C and E are the most common antioxidants, Quercetin, Xanthohumol, isoxanthohumol, kaempferol, myricertin and genistein are the most common flavonoid antioxidants.
Nonflavonoids are found in red wine just as flavonoids are. The most popular one is resveratrol.