Phytochemical

thumb|Red, blue, and purple colors of berries derive mainly from [[polyphenol phytochemicals called anthocyanins.]]

thumb|[[Cucurbita fruits, including squash and pumpkin, typically have high content of the phytochemical pigments called carotenoids.]]

Phytochemicals are naturally occurring chemicals present in or extracted from plants. Some phytochemicals are nutrients for the plant, while others are metabolites produced to enhance plant survivability and reproduction.

The fields of extracting phytochemicals for manufactured products or applying scientific methods to study phytochemical properties are called phytochemistry. Further, the bioavailability of many phytochemical metabolites appears to be low, as they are rapidly excreted from the body within minutes.

Definition

Phytochemicals 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 predators. As components of plants, all individual phytochemicals make up the whole plant as it exists in nature.

Phytochemicals are generally 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, stilbenes or lignans. and 130,000 phytochemicals have been discovered.

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 in vitro studies or in vivo studies using laboratory animals. no non-nutrient phytochemical has sufficient scientific evidence in humans for an approved health claim.

History of uses

thumb|Berries of Atropa belladonna, also called deadly nightshade, containing the toxic phytochemicals, tropane alkaloids

Without specific knowledge of their cellular actions or mechanisms, phytochemicals are used in traditional medicine (though some can be toxic). 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 Atropa belladonna were used as poisons, and early humans made poisonous arrows from the plant. Other uses include perfumes, such as the sesquiterpene santolols, from sandalwood.

The 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 a cancer drug. 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.

Non-digestible dietary fibers from plant foods, often considered as a phytochemical, and coronary heart disease.

Phytochemical dietary supplements are neither recommended by health authorities for improving health nor are they 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. 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 disease.

Among carotenoids such as the tomato phytochemical, lycopene, the US 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. 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), which are necessary to avoid illness from cyanogenic glycosides present in unprocessed cassava.

References

External links

Dr. Duke's Phytochemical and Ethnobotanical Databases – United States Department of Agriculture