Over 4,000 flavonoids have been identified, many of which occur in fruits, vegetables and beverages (tea, coffee, beer, wine and fruit drinks). According to chemical structure, flavonoids are categorized, into flavonols, flavones, flavanones, isoflavones, catechins, anthocyanidins and chalcones. Flavonoids are being researched, due to their potential beneficial effects on human health – they have been reported to have antiviral, anti-allergic, antiplatelet, anti-inflammatory, antitumor and antioxidant activities.
Antioxidants are compounds that protect cells against the damaging effects of free radicals. An imbalance between antioxidants and free radicals results in oxidative stress, leading to cellular damage. Oxidative stress has been linked to cancer, aging, atherosclerosis, ischemic injury, inflammation and neurodegenerative diseases (Parkinson's and Alzheimer's). Flavonoids may help provide protection against these diseases by contributing, along with antioxidant vitamins and enzymes, to the total antioxidant defense system of the human body. Epidemiological studies have shown that flavonoids in your daily diet is inversely related to mortality from coronary heart disease and to the incidence of heart attacks.
Recent studies have demonstrated that flavonoids found in fruits and vegetables may also act as antioxidants. Like alpha-tocopherol (vitamin E), flavonoids contain chemical structural elements that may be responsible for their antioxidant activities.