*3.3.3 Flavonoids*

Flavonoids are secondary metabolisms belonging to the polyphenol group, consist of two phenyl rings and a heterocyclic ring, and abbreviated C6-C3-C6. Flavonoids are commonly flavones, flavonols, flavanones, flavanonols, flavanols or catechins, anthocyanins, and chalcones [63, 64]. Flavonoids exist in almost various plants and possess high bioactivities in *Morinda* L. [65]. Flavonoids in *Morinda* are antioxidants having the ability against cardiovascular disease and cell components degeneration that age-related [66]. The mainly antioxidant properties of flavonoids are based on a role against free radicals (hydroxyl and superoxide radicals) via scavenging of reactive species and inhibiting biomolecular damage [67]. Besides, flavonoids also exhibit various bioactivities, such as anti-diabetic, anti-inflammatory, cardioprotective activity, anti-age-dependent-neuropathology activity, anti-cancer activity, and anti-viral/ bacterial [68]. Flavonoids content corresponds 5 to 10%, compared to the secondary metabolites in plants, and nowadays, there are about 5000 identified flavonoids. Some studies presented an intake dose of flavonoids per day is from 20 mg and 500 mg [69].
