- Flavonoids are a class of plant secondary metabolites found ubiquitously in plants. Over 4,000 flavonoids have been identified belonging to subclasses like flavonols, flavones, flavanones. - Common dietary sources of flavonoids include fruits, vegetables, tea, wine and other plant-based beverages. Extraction methods depend on flavonoid polarity, with non-polar flavonoids extracted by organic solvents and polar glycosides by alcohols. - Structural determination methods include analyzing hydroxyl group content, degradation reactions with alkali to identify subunits, and confirmation via synthesis. Color reactions like the Shinoda test can also indicate flavone, flavonoid