vegetables are also rich in a carotenoid called beta–
carotene. Flavonoids are other reddish pigments,
found in red grape skins and citrus fruits. Other phy-
topigments include lutein that makes corn yellow, and
lycopene that makes tomatoes red. Aroma com-
pounds in garlic and onions help protect plants from
bacterial and viral infections. Others are enzyme
blockers that forme to fight toxic pollutants. Plants
have developed literally hundreds of thousands of
naturally phyto–protective chemicals. It is therefore
believed that if people consume them, they may gain
some of these protective benefits. When extracted
from plants, isolated phytochemicals are grouped
into distinctive classes depending on the number and
kind of atoms that they contain and according to the
chemical structure of their main functional groups.
The main classes of phytochemicals are:
Alkaloids. This class contains molecules with cyclic
carbon groups containing at least one nitrogen atom
in the carbon ring. They are obtained chiefly from
many vascular plants and some fungi and include
steroids and some saponins extracted from beans,
cereals, herbs.
Aromatics. This class includes substances that con-
tain a benzene ring that consists of six carbon atoms
in a flat, hexagonal pattern and are found in aro-
matic plants such as garlic and onions.
Flavonoids. Many are extracted from fruits, and
vegetables. They include flavones (found in chamo-
mile), flavonols (found in grapefruit and rutin-buck-
wheat), flavanones (from citrus fruits, milk thistle)
and the isoflavones (found in soy, peanuts, lentils).
Indoles. Indoles, extracted from cabbage, are carbon
compounds with two rings, a six-membered benzene
ring fused to a five-membered nitrogen–containing
pyrrole ring.
Phytosterols. Sterols can be extracted from most
plant species. Although green and yellow vegetables
contain significant amounts, their seeds concentrate
the sterols. Most of the research on phytosterols has
been done on the seeds of pumpkins, yams, soy, rice
and herbs.
Terpenes. These are extracted from green vegetables,
soy products and grains, and represent one of the
largest classes of phytochemicals. The most intensely
studied terpenes are carotenoids (from fruits, car-
rots). A subclass of terpenes are the limonoids
found in citrus fruit peels.
It is well-known that plants produce phytochem-
icals to protect themselves and recent research increas-
ingly shows that they may protect humans as well.
Some examples of their health benefits include:Antioxidative properties. Most phytochemicals show
antioxidant activity and are thus liable to protect
lipids, blood and other body fluids from damage
(oxidative stress) from reactive oxygen species while
reducing the risk of developing certain types of can-
cer. Phytochemicals with antioxidant activity include
allyl sulfides (onions, leeks, garlic), carotenoids, fla-
vonoids, and polyphenols (tea, grapes).
Hormonal properties. Isoflavones, also called phy-
toestrogens may function as human estrogens and
helptoreducemenopausalsymptomsandosteoporosis.
Enzyme stimulation. Indoles stimulate enzymes that
lower the activity of estrogen and could reduce the
risk for breast cancer. Other phytochemicals, which
interfere with enzymes, are protease inhibitors (soy
and beans) and terpenes.
Interference with DNA replication. Saponins inter-
fere with the replication of cell DNA, thereby pre-
venting the multiplication of cancer cells. Capsaicin,
found in hot peppers, is believed to protect DNA
from carcinogens.
Antibacterial properties. The phytochemical allicin
from garlic has antibacterial properties. The intake
of proanthocyanidins (from cranberries) will reduce
the risk of urinary tract infections and will improve
dental health.
Cholesterol control. Phytosterols are believed to
compete with dietary cholesterol for uptake in the
intestines.
Adhesion properties. Some phytochemicals bind to
cell walls and it has been suggested that they prevent
the adhesion of pathogens to human cell walls.
Proanthocyanidins are responsible for the anti–
adhesion properties of cranberry.Medicinal plants
Medicinal plants have been used since the dawn of
history to prevent and treat various diseases and disor-
ders. They were first discovered by trial and error, for
instance by noticing that pain went away when drinking
tea made from the bark of a willow tree. It is only much
later as science developed in the 20th century that
chemists isolated salicylic acid from willow bark, the
active ingredient in aspirin. Of the estimated 250,000
plant species, only 2% have been thoroughly investi-
gated for phytochemicals with potential medicinal use.
Some of the most well-known include:
Aloe vera (Aloe vera). Heals wounds, emollient,
laxative.
Angelica (Angelica arcangelica). Antispasmodic,
promotes menstrual flow.Phytonutrients