Flavonoids are one of the largest groups of plant phenolic compounds, known for their diverse biological roles in plants and health benefits in humans. They are secondary metabolites widely distributed in fruits, vegetables, flowers, bark, and leaves.
Key Features of Flavonoids
- Basic structure: C₆–C₃–C₆ (two aromatic rings linked by a three-carbon bridge).
- Belong to the polyphenol family.
- Responsible for pigmentation, UV protection, and defense in plants.
Major Classes of Flavonoids
- Flavonols – quercetin, kaempferol (in onions, kale).
- Flavones – apigenin, luteolin (in parsley, celery).
- Flavanones – naringenin, hesperidin (in citrus fruits).
- Isoflavones – genistein, daidzein (in soybeans).
- Anthocyanidins – cyanidin, delphinidin (in berries, grapes, red cabbage).
- Flavanols (Catechins) – epicatechin, EGCG (in green tea, cocoa).
Roles in Plants
- Pigmentation → attract pollinators (anthocyanins).
- Defense → antimicrobial, antifungal, anti-herbivory.
- UV Protection → absorb harmful UV radiation.
- Growth Regulation → modulate hormones and signaling.
Health Benefits for Humans
- Antioxidant → neutralize ROS, protect against oxidative stress.
- Anti-inflammatory → reduce risk of chronic diseases.
- Cardioprotective → improve blood vessel function, lower blood pressure.
- Anticancer → some flavonoids inhibit tumor growth.
- Neuroprotective → improve memory and brain health.