Flavonoids have a common structure consisting of 2 aromatic rings that are linked together by 3 carbon atoms that form an oxygenated heterocycle. This large group, which constitutes the most prevalent in the human diet, is divided into 6 subgroups, including flavonols (. quercetin), flavones (. apigenin), isoflavones (. daidzein), flavanones (. hesperetin), anthocyanidins (. cyanidin), and flavanols (catechins and proanthocyanidins). Non- flavonoid polyphenolics include phenolic acids (. chlorogenic acid), lignans (. secoisolariciresinol) and stilbenes (. resveratrol) (Manach et al., 2004). .
