**3.2 Flavonoids**

Like as phenolic acids, flavonoids are secondary metabolites of plants with polyphenolic structure. Flavonoids consist of a 15-carbon skeleton organized by a three-carbon chain (C6–C3–C6 structure) and they are the most diverse compounds in the plant kingdom. Flavonoids can be classified in to several sub-classes including flavanols, flavones, flavones, isoflavones and anthocyanins. The most common flavonoids of rice belong to a wide variety of sub-families such as flavonols, flavones, flavanols, flavanons, and anthocyanins.
