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Phytochemical

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Red, blue, and purple colors of berries derive mainly from polyphenol phytochemicals called anthocyanins.
Cucurbita fruits, including squash and pumpkin, typically have high content of the phytochemical pigments called carotenoids.

Phytochemicals are chemical compounds produced by plants, generally to help them resist fungi, bacteria and plant virus infections, and also consumption by insects and other animals. The name comes from Greek φυτόν (phyton) 'plant'. Some phytochemicals are both poisonous and medically therapeutic.

As a term, phytochemicals is generally used to describe plant compounds that are under research with unestablished effects on health, and are not typically considered essential nutrients. Regulatory agencies governing food labeling in Europe and the United States have provided guidance for industry to limit or prevent health claims about phytochemicals on food product or nutrition labels.

Definition

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Phytochemicals are chemical constituents of plant origin.[1] Phytochemicals (from Greek phyto, meaning "plant") are chemicals produced by plants through primary or secondary metabolism.[2][3] They generally have biological activity in the plant host and play a role in plant growth or defense against competitors, pathogens, or predators.[2]

Phytochemicals are generally regarded as research compounds rather than essential nutrients because proof of their possible health effects has not been established yet.[4][5] Phytochemicals under research can be classified into major categories, such as carotenoids[6] and polyphenols, which include phenolic acids, flavonoids, stilbenes or lignans.[5] Flavonoids can be further divided into groups based on their similar chemical structure, such as anthocyanins, flavones, flavanones, isoflavones, and flavanols.[5][7] Flavanols are further classified as catechins, epicatechins, and proanthocyanidins.[5][7] In total, between 50,000[8] and 130,000[9] phytochemicals have been discovered.

The greatest challenge to the phytochemist lies in extracting and identifying the specific compound(s) responsible for the observed effect, defining their mode of action and finally delineating a useful function for the phytochemical or its derivatives as, for example, a therapeutic drug.[2] Challenges in the field include isolating specific compounds and determining their structures, which are often complex, and identifying what specific phytochemical is primarily responsible for any given biological activity.[2][10][11] The Phytochemical Society of North America (PSNA)[12] is a nonprofit scientific organization with membership open to those interested in plant biochemistry, phytochemistry, and the role of plant substances in related disciplines.

History of uses

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Berries of Atropa belladonna, also called deadly nightshade

Since the start of civilization, humans have been reliant on the plant kingdom. Historical records suggest that they have been continuously domesticating plants and utilizing various plant parts as food, medicine (traditional and scientific), cosmetics and perfumes. They have also been using plants to find remedies for their diseases and health issues.[13]

By the initiation of the 18th century, the scientific community was quite enthusiastic about investigating the chemical constituents of plants. With the help of fundamental chemical techniques of separation and chromatography, they were able to isolate several molecules of pharmacological importance. The 20th and 21st centuries provided further thrust in the research and development of phytochemistry and yielded several more phytochemicals of immense importance to medical science.[13]

Without specific knowledge of their cellular actions or mechanisms, the complexities involved in unraveling the specific roles of phytochemicals in plant protection have also led use of plant material as both poison in folklore and as therapeutic drugs in modern 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.[14][15] Conversely, the tropane alkaloids of Atropa belladonna were used as poisons, and early humans made poisonous arrows from the plant.[16][17] Other uses include perfumes, such as the sequiterpene santolols, from sandalwood.[18]

Phytochemicals such as rhizoxin, ansamitocin derivatives, and arenastatin, along with other natural ligands, interact with tubulin at specific binding sites, demonstrating cytotoxic (cell-killing) effects on tumor cells and potential for studying microtubule dynamics and drug resistance mechanisms in both fungi and mammalian systems.[2]

The English yew tree was long known to be extremely and immediately toxic to animals that grazed on its leaves or occasionally in humans, especially children, who may be attracted to the colorful fruits containing the poisonous seeds; however, in 1971, paclitaxel was isolated from it, subsequently becoming an important cancer drug.[2]

The biological activities for most plant-based compounds are largely complex, evidence that these effects are due to specific nutrients or phytochemicals is limited.[2][5] Phytochemicals with established roles in the body are classified as essential nutrients.[4][19]

Functions

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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 in humans.[19][20]

Some phytochemicals are known phytotoxins that are toxic to humans;[21][22] for example aristolochic acid is carcinogenic at low doses.[23] Some phytochemicals, such as caffeine, could act as antinutrients that interfere with the absorption of nutrients such as iron in some individuals.[24] Others, such as some polyphenols and flavonoids, may be pro-oxidants when ingested in high amounts.[25]

Non-digestible dietary fibers from plant foods, often considered as a phytochemical,[26] are now generally regarded as a nutrient group having approved health claims for reducing the risk of some types of cancer[27] and coronary heart disease.[28]

Eating a diet high in fruits, vegetables, grains, legumes and plant-based beverages has long-term health benefits,[19] but there is no evidence that taking dietary supplements of non-nutrient phytochemicals extracted from plants similarly benefits health.[4] Phytochemical supplements are neither recommended by health authorities for improving health[5][29] nor approved by regulatory agencies for health claims on product labels.[30][31]

Consumer and industry guidance

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While there is ample evidence to support diets rich in fruit, vegetables, whole grains, legumes, and nuts to improve and maintain health,[19] evidence that such effects result from specific nutrients or phytochemicals is limited.[4] For example, systematic reviews and/or meta-analyses indicate weak reduction from a high intake of fruits and fruit and vegetables combined, but not vegetables alone, on having a significant effect on breast, lung, or bladder cancers - holistic lifestyle choices, such as smoking cessation, seemed to have a greater mitigating effect on most cancers than eating fruits and vegetables only.[32][33] 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 fibrous lignins, antioxidants, and carotenes.[34]

Phytochemicals, such as polyphenols, have been specifically discouraged from food labeling in Europe and the United States because there is limited scientific evidence for a cause-and-effect relationship between dietary polyphenols and inhibition or prevention of any disease.[30][35]

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.[36][37]

Phytochemicals, while beneficial to the plants that produce them, can have adverse effects on other organisms, leading to perceptions of them as "good" or "bad" depending on perspective. Their toxic properties, often stigmatized, can provide critical insights into biological functions and potential therapeutic uses. Exploring these "bad" properties, such as toxicity in animals, could reveal valuable "good" qualities, such as their potential as drugs, especially when considering individual genetic and metabolic differences in humans.[2]

Effects of food processing

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Phytochemicals in freshly harvested plant foods may be degraded by processing techniques, including cooking.[38] The main cause of phytochemical loss from cooking is thermal decomposition.[38]

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.[39] Food processing techniques like mechanical processing can also free carotenoids and other phytochemicals from the food matrix, increasing dietary intake.[38][40]

In some cases, processing of food is necessary to reduce inherent plant toxins in fruits and vegetables; for example societies that eat cassava as a dietary staple never consume the tuberous roots raw and have methods of peeling, cooking, and processing which are necessary to reduce the cyanide content to non-toxic levels. Generally the cyanide content is substantially higher in the cassava peel which is inedible.[41] Similarly, depending on the individual's genetic and metabolic functioning, certain parts of the rhubarb plant may cause liver toxicity (hepatoxicity).[42]

See also

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References

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  1. ^ Breslin, Andrew (2017). "The Chemical Composition of Green Plants". Sciencing, Leaf Group Ltd.
  2. ^ a b c d e f g h Molyneux, Russell J.; Lee, Stephen T.; Gardner, Dale R.; Panter, Kip E.; James, Lynn F. (2007-11-01). "Phytochemicals: The good, the bad and the ugly?". Phytochemistry. Highlights in the Evolution of Phytochemistry: 50 Years of the Phytochemical Society of Europe. 68 (22): 2973–2985. doi:10.1016/j.phytochem.2007.09.004. ISSN 0031-9422.
  3. ^ Harborne, Jeffrey B.; Baxter, Herbert; Moss, Gerard P., eds. (1999). "General Introduction". Phytochemical dictionary a handbook of bioactive compounds from plants (2nd ed.). London: Taylor & Francis. p. vii. ISBN 9780203483756.
  4. ^ a b c d "Phytochemicals". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, Oregon. 2017. Retrieved 12 February 2017.
  5. ^ a b c d e f Heneman, Karrie; Zidenberg-Cherr, Sheri (2008). "Publication 8313: Phytochemicals" (PDF). University of California Cooperative Extension.
  6. ^ "Carotenoids". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, Oregon. July 2016. Retrieved 12 February 2017.
  7. ^ a b "Flavonoids". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, Oregon. November 2015. Retrieved 12 February 2017.
  8. ^ Afendi, Farit Mochamad; Okada, Taketo; Yamazaki, Mami; et al. (February 2012). "KNApSAcK Family Databases: Integrated Metabolite–Plant Species Databases for Multifaceted Plant Research". Plant and Cell Physiology. 53 (2): e1. doi:10.1093/pcp/pcr165. PMID 22123792.
  9. ^ Rutz, Adriano; Sorokina, Maria; Galgonek, Jakub; et al. (26 May 2022). "The LOTUS initiative for open knowledge management in natural products research". eLife. 11: e70780. doi:10.7554/eLife.70780. PMC 9135406. PMID 35616633.
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  11. ^ Price, J. R.; Lamberton, J. A.; Culvenor, C.C.J (1992), "The Australian Phytochemical Survey: historical aspects of the CSIRO search for new drugs in Australian plants. Historical Records of Australian Science, 9(4), 335–356", Historical Records of Australian Science, 9 (4), Australian Academy of Science: 335, 336, doi:10.1071/hr9930940335
  12. ^ dev. "Home - Welcome to PSNA". Retrieved 2025-01-19.
  13. ^ a b Sinha, Dwaipayan; Odoh, Uchenna Estella; Ganguly, Sharmistha; Muhammad, Murad; Chatterjee, Moumita; Chikeokwu, Ikenna; Egbuna, Chukwuebuka (2023-01-01), Egbuna, Chukwuebuka; Rudrapal, Mithun; Tijjani, Habibu (eds.), "Chapter 1 - Phytochemistry, history, and progress in drug discovery", Phytochemistry, Computational Tools and Databases in Drug Discovery, Drug Discovery Update, Elsevier, pp. 1–26, doi:10.1016/b978-0-323-90593-0.00001-0, ISBN 978-0-323-90593-0, retrieved 2025-01-19
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  16. ^ Michael (1998). Alkaloids : biochemistry, ecology, and medicinal applications. New York: Plenum Press. p. 20. ISBN 978-0-306-45465-3.
  17. ^ Timbrell, John (2005). The poison paradox : chemicals as friends and foes. Oxford: Oxford Univ. Pr. pp. 2. ISBN 978-0-19-280495-2. poisons used by the wife of Claudius.
  18. ^ Ellena 2022, pp. 12–15.
  19. ^ a b c d "Why is it important to eat vegetables? Nutrients". ChooseMyPlate.gov, USDA Center for Nutrition Policy & Promotion, US Department of Agriculture. 16 January 2016. Archived from the original on 16 August 2019. Retrieved 12 February 2017.
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  21. ^ Iwasaki, S (April 1998). "Natural organic compounds that affect to microtubule functions". Yakugaku Zasshi. 118 (4): 112–26. doi:10.1248/yakushi1947.118.4_111. PMID 9564789.
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  30. ^ a b EFSA Panel on Dietetic Products, Nutrition and Allergies (2010). "Scientific Opinion on the substantiation of health claims related to various food(s)/food constituent(s) and protection of cells from premature aging, antioxidant activity, antioxidant content and antioxidant properties, and protection of DNA, proteins and lipids from oxidative damage pursuant to Article 13(1) of Regulation (EC) No 1924/20061". EFSA Journal. 8 (2): 1489. doi:10.2903/j.efsa.2010.1489.
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  33. ^ Smith-Warner, S. A.; Spiegelman, D; Yaun, S. S.; Albanes, D; Beeson, W. L.; Van Den Brandt, P. A.; Feskanich, D; Folsom, A. R.; Fraser, G. E.; Freudenheim, J. L.; Giovannucci, E; Goldbohm, R. A.; Graham, S; Kushi, L. H.; Miller, A. B.; Pietinen, P; Rohan, T. E.; Speizer, F. E.; Willett, W. C.; Hunter, D. J. (2003). "Fruits, vegetables and lung cancer: A pooled analysis of cohort studies". International Journal of Cancer. 107 (6): 1001–11. doi:10.1002/ijc.11490. PMID 14601062. S2CID 28381529.
  34. ^ "Electronic Code of Federal Regulations, Title 21, Chapter I, Subchapter B, Part 101.78. Health claims: fruits and vegetables and cancer". US Government Printing Office. 9 February 2017. Retrieved 12 February 2017.
  35. ^ Gross P (1 March 2009), New Roles for Polyphenols. A 3-Part Report on Current Regulations & the State of Science, Nutraceuticals World, retrieved 12 February 2017
  36. ^ Schneeman BO (9 July 2015). "Qualified Health Claims: Letter Regarding "Tomatoes and Prostate, Ovarian, Gastric and Pancreatic Cancers (American Longevity Petition)" (Docket No. 2004Q-0201)". Office of Nutritional Products, Labeling and Dietary Supplements, Center for Food Safety and Applied Nutrition, US Food and Drug Administration. Retrieved 12 February 2017.
  37. ^ Program, Human Foods (2024-09-03). "Qualified Health Claims: Letters of Denial". FDA.
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  39. ^ Dewanto, V; Wu, X; Adom, KK; Liu, RH (2002). "Thermal processing enhances the nutritional value of tomatoes by increasing total antioxidant activity". Journal of Agricultural and Food Chemistry. 50 (10): 3010–4. doi:10.1021/jf0115589. PMID 11982434.
  40. ^ Hotz, C; Gibson, R. S. (2007). "Traditional food-processing and preparation practices to enhance the bioavailability of micronutrients in plant-based diets". The Journal of Nutrition. 137 (4): 1097–100. doi:10.1093/jn/137.4.1097. PMID 17374686.
  41. ^ Contents: Roots, tubers, plantains and bananas in human nutrition. Rome: FAO. 1990. Chapter 7: Cassava toxicity
  42. ^ Li, Shanze; Wang, Yuming; Li, Chunyan; Yang, Na; Yu, Hongxin; Zhou, Wenjie; Chen, Siyu; Yang, Shenshen; Li, Yubo (2021-05-04). "Study on Hepatotoxicity of Rhubarb Based on Metabolomics and Network Pharmacology". Drug Design, Development and Therapy. 15: 1883–1902. doi:10.2147/DDDT.S301417. PMC 8106470. PMID 33976539.{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)

Further reading

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