ABSTRACT
The data from both experimental and epidemiological studies show that grains, vegetables, and fruits contain a large variety of substances called “plant chemicals” or “
phytochemicals
.” The term
phytochemical
refers to every naturally occurring chemical substance present in plants, especially those that are biologically active. Major phytochemicals include
phenolic acids
,
flavonoids
, and
coumarin derivatives
, as well as many other
polyphenols
. The antioxidant activities in these phytochemicals range from extremely slight to very great. The natural antioxidants may have one or more of the following roles:
• Free-radical scavengers • Reducing agents • Potential complexers of prooxidant metals • Quenchers of singlet oxygen
Consequently, phytochemical dietary components may actively contribute to the control of oxidative reactions and provide protection
in vivo
. Antioxidants play an important role in preventing undesirable changes in flavor and nutritional quality of foods. Cereal grains provide significant quantities of energy, protein, and selected micronutrients to the animal and human diet. The chemical composition and bioavailability of nutrients varies between species and varieties of grains and may be affected by forms of processing as feed and food. Cereal grains are rich in phenolic acids; the total amounts may approach 500 mg/kg of edible cereals. Other phytochemicals occurring in cereals are
phytosterines
,
saponins
, and
phytoestrogens
. In cereals, flavonoids are present in small quantities. Barley contains measurable amounts of
catechins
and some di-and trimer
procyanidins
.
