a. FlavonoidsFlavonoids, which are

a. Flavonoids
Flavonoids, which are natural pigments found in
vegetables, have a protective effect against the damage
caused by oxidizing agents, such as UV radiation and air
pollution, among others. Since the human body cannot
produce these protective chemical substances, flavonoids
must be obtained through food or dietary supplements.
They are found in a wide range of plants, fruits, vegetables,
and beverages and are substantial constituents of the
nonenergetic part of the human diet.
Flavonoids have a variable number of phenolic hydroxyl
groups in their chemical structure and are excellent
chelators of iron and other transition metals, making
them efficient antioxidants. Consequently, they play an
essential role in protecting the body against oxidative
damage. They also have therapeutic effects in a large
number of diseases, including ischemic heart disease,
atherosclerosis, and cancer.26
Depending on their
structural characteristics, flavonoids are classified into
the following groups: 1) flavanols, such as catechin;
2) flavonols, such as quercetin; 3) flavones, such as
diosmetin; and 4) anthocyanidins.