Phytochemicals are chemical compounds produced by plants, generally to
help them thrive or thwart competitors, predators, or pathogens. The
name comes from the Greek word phyton, meaning plant. Some
phytochemicals have been used as poisons and others as traditional
As a term, phytochemicals is generally used to describe plant
compounds that are under research with unestablished effects on health
and are not scientifically defined as essential nutrients. Regulatory
agencies governing food labeling in Europe and the United States have
provided guidance for industry limiting or preventing health claims
about phytochemicals on food product or nutrition labels.
2 History of uses
4 Consumer and industry guidance
5 Effects of food processing
6 See also
8 Further reading
9 External links
Plants are composed entirely of chemicals of various kinds.
Phytochemicals (from Greek phyto, meaning "plant") are chemicals
produced by plants through primary or secondary metabolism. They
generally have biological activity in the plant host and play a role
in plant growth or defense against competitors, pathogens, or
Phytochemicals generally are regarded as research compounds rather
than essential nutrients because proof of their possible health
effects has not been established yet. Phytochemicals under
research can be classified into major categories, such as
carotenoids and polyphenols, which include phenolic acids,
flavonoids, and stilbenes/lignans.
Flavonoids can be further
divided into groups based on their similar chemical structure, such as
anthocyanins, flavones, flavanones, and isoflavones, and
Flavanols further are classified as catechins,
epicatechins, and proanthocyanidins.
Phytochemists study phytochemicals by first extracting and isolating
compounds from the origin plant, followed by defining their structure
or testing in laboratory model systems, such as cell cultures, in
vitro experiments, or in vivo studies using laboratory animals.
Challenges in that field include isolating specific compounds and
determining their structures, which are often complex, and identifying
what specific phytochemical is primarily responsible for any given
History of uses
Berries of Atropa belladonna, also called deadly nightshade
Without specific knowledge of their cellular actions or mechanisms,
phytochemicals have been used as poison and in traditional medicine.
For example, salicin, having anti-inflammatory and pain-relieving
properties, was originally extracted from the bark of the white willow
tree and later synthetically produced to become the common,
over-the-counter drug, aspirin. The tropane alkaloids of A.
belladonna were used as poisons, and early humans made poisonous
arrows from the plant. In Ancient Rome, it was used as a poison by
Agrippina the Younger, wife of Emperor
Claudius on advice of Locusta,
a lady specialized in poisons, and Livia, who is rumored to have used
it to kill her husband Emperor Augustus.
English yew tree was long known to be extremely and immediately
toxic to animals that grazed on its leaves or children who ate its
berries; however, in 1971, paclitaxel was isolated from it,
subsequently becoming an important cancer drug.
As of 2017, the biological activities for most phytochemicals are
unknown or poorly understood, in isolation or as part of foods.
Phytochemicals with established roles in the body are classified as
The phytochemical category includes compounds recognized as essential
nutrients, which are naturally contained in plants and are required
for normal physiological functions, so must be obtained from the diet
Some phytochemicals are known phytotoxins that are toxic to
humans; for example aristolochic acid is carcinogenic at low
doses. Some phytochemicals are antinutrients that interfere with
the absorption of nutrients. Others, such as some polyphenols and
flavonoids, may be pro-oxidants in high ingested amounts.
Nondigestible dietary fibers from plant foods, often considered as a
phytochemical, are now generally regarded as a nutrient group
having approved health claims for reducing the risk of some types of
cancer and coronary heart disease.
Eating a diet high in fruits, vegetables, grains, legumes and
plant-based beverages has long-term health benefits, but there is
no evidence that taking dietary supplements of non-nutrient
phytochemicals extracted from plants similarly benefits health.
Phytochemical supplements are neither recommended by health
authorities for improving health nor approved by regulatory
agencies for health claims on product labels.
Consumer and industry guidance
While health authorities encourage consumers to eat diets rich in
fruit, vegetables, whole grains, legumes, and nuts to improve and
maintain health, evidence that such effects result from specific,
non-nutrient phytochemicals is limited or absent. For example,
systematic reviews and/or meta-analyses indicate weak or no evidence
for phytochemicals from plant food consumption having an effect on
breast, lung, or bladder cancers. Further, in the United
States, regulations exist to limit the language on product labels for
how plant food consumption may affect cancers, excluding mention of
any phytochemical except for those with established health benefits
against cancer, such as dietary fiber, vitamin A, and vitamin C.
Phytochemicals, such as polyphenols, have been specifically
discouraged from food labeling in Europe and the United States because
there is no evidence for a cause-and-effect relationship between
dietary polyphenols and inhibition or prevention of any
Among carotenoids such as the tomato phytochemical, lycopene, the US
Food and Drug Administration
Food and Drug Administration found insufficient evidence for its
effects on any of several cancer types, resulting in limited language
for how products containing lycopene can be described on labels.
Effects of food processing
Phytochemicals in freshly harvested plant foods may be degraded by
processing techniques, including cooking. The main cause
of phytochemical loss from cooking is thermal decomposition.
A converse exists in the case of carotenoids, such as lycopene present
in tomatoes, which may remain stable or increase in content from
cooking due to liberation from cellular membranes in the cooked
food. Food processing techniques like mechanical processing can
also free carotenoids and other phytochemicals from the food matrix,
increasing dietary intake.
In some cases, processing of food is necessary to remove phytotoxins
or antinutrients; for example societies that use cassava as a staple
have traditional practices that involve some processing (soaking,
cooking, fermentation, etc.), which are necessary to avoid getting
sick from cyanogenic glycosides present in unprocessed cassava.
List of antioxidants in food
List of phytochemicals in food
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Media related to Phytochemicals at Wikimedia Commons
Phytochemical and Ethnobotanical Databases – United
States Department of Agriculture
Types of phytochemicals
Types of Terpenes and Terpenoids (# of isoprene units)
Acyclic (linear, cis and trans forms)
Monocyclic (single ring)
Bicyclic (2 rings)
Iridoids (cyclopentane ring)
Iridoid glycosides (iridoids bound to a sugar)
Steroids (4 rings)
Pinene (β and α
Cholecalciferol (Vit D)
sap, resins, latex of many plants, e.g. rubber
Terpene synthase enzymes (many), having in common a
Terpene synthase N
terminal domain (protein domain)
Activated isoprene forms
Isopentenyl pyrophosphate (IPP)
Dimethylallyl pyrophosphate (DMAPP)
Types of phenolic compounds
Types of polyphenols
Types of flavonoids
Apigenin, Chrysin, et.c.
Quercetin, Kaempferol, et.c.
Catechin, Gallocatechol, et.c.
Apiforol, Luteoforol, et.c.
Leucocyanidin, Leucodelphinidin, et.c.
Cyanidin, Delphinidin, et.c.
Apigeninidin, Guibourtinidin, et.c.
Butein, Isoliquiritigenin, et.c.
List of phytochemicals in food
Types of natural tannins
Pyrocatecollic type tannins
Coumarins and isocoumarins
p-Hydroxybenzoic acid glucoside
Dihydroxybenzoic acid (Hypogallic acid)
Phloroglucinol carboxylic acid
Other phenolic acids
Aromatic amino acids
Precursor to isothiocyanates
Saturated cyclic acids
List of phytochemicals and foods in which