Phytonutrients are natural phytochemicals in plants. These chemicals help protect plants from germs, fungi, bugs, and other threats. 

Phytonutrients are not essential, but they may help prevent disease.

More than 25,000 phytochemicals are found in plant foods, and 6 important phytonutrients are: 

• Carotenoids
• Ellagic acid
• Flavonoids
• Resveratrol
• Glucosinolates
• Phytoestrogens

Flavonoids (or bioflavonoids) are a class of polyphenolic secondary metabolites found in plants. Their carbon structure can be abbreviated C6-C3-C6. Flavonoids can be classified into:

1. bioflavonoids,
2. isoflavonoids, derived from 3-phenylchromen-4-one (3-phenyl-1,4-benzopyrone) structure
3. neoflavonoids, derived from 4-phenylcoumarine (4-phenyl-1,2-benzopyrone) structure

Flavonoids are the most important plant pigments for flower coloration, producing yellow or red/blue pigmentation in petals designed to attract pollinator animals.

In higher plants, flavonoids are involved in UV filtration, symbiotic nitrogen fixation, and floral pigmentation. They may also act as chemical messengers, physiological regulators, and cell cycle inhibitors. Flavonoids secreted by the root of their host plant help Rhizobia in the infection stage of their symbiotic relationship with legumes like peas, beans, clover, and soy. Some flavonoids have inhibitory activity against organisms that cause plant diseases.