Phytochemistry
{{Short description|Study of phytochemicals, which are chemicals derived from plants}}
{{For|the journal|Phytochemistry (journal)}}
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Phytochemistry is the study of phytochemicals, which are chemicals derived from plants. Phytochemists strive to describe the structures of the large number of secondary metabolites found in plants, the functions of these compounds in human and plant biology, and the biosynthesis of these compounds. Plants synthesize phytochemicals for many reasons, including to protect themselves against insect attacks and plant diseases. The compounds found in plants are of many kinds, but most can be grouped into four major biosynthetic classes: alkaloids, phenylpropanoids, polyketides, and terpenoids.
Phytochemistry can be considered a subfield of botany or chemistry. Activities can be led in botanical gardens or in the wild with the aid of ethnobotany. Phytochemical studies directed toward human (i.e. drug discovery) use may fall under the discipline of pharmacognosy, whereas phytochemical studies focused on the ecological functions and evolution of phytochemicals likely fall under the discipline of chemical ecology. Phytochemistry also has relevance to the field of plant physiology.
Techniques
Techniques commonly used in the field of phytochemistry are extraction, isolation, and structural elucidation (MS,1D and 2D NMR) of natural products, as well as various chromatography techniques (MPLC, HPLC, and LC-MS).
Phytochemicals
Many plants produce chemical compounds for defence against herbivores. The major classes of pharmacologically active phytochemicals are described below, with examples of medicinal plants that contain them.{{cite encyclopedia |title=Angiosperms: Division Magnoliophyta: General Features |encyclopedia=Encyclopædia Britannica (volume 13, 15th edition) |year=1993 |page=609 }} Human settlements are often surrounded by weeds containing phytochemicals, such as nettle, dandelion and chickweed.{{cite book |author=Meskin, Mark S. |title=Phytochemicals in Nutrition and Health |publisher=CRC Press|year=2002 |isbn=978-1-58716-083-7 |page=123 |url=https://books.google.com/books?id=cJHsMALUDj0C&pg=PA123}}{{cite book |author1=Springbob, Karen |author2=Kutchan, Toni M. |chapter=Introduction to the different classes of natural products|editor=Lanzotti, Virginia |title=Plant-Derived Natural Products: Synthesis, Function, and Application |publisher=Springer |year=2009 |isbn=978-0-387-85497-7 |page=3 |chapter-url=https://books.google.com/books?id=Y8SpVXEng4QC&pg=PA3}}
Many phytochemicals, including curcumin, epigallocatechin gallate, genistein, and resveratrol are pan-assay interference compounds and are not useful in drug discovery.{{cite journal|last1=Baell|first1=Jonathan|last2=Walters|first2=Michael A.|title=Chemistry: Chemical con artists foil drug discovery|journal=Nature|date=24 September 2014|volume=513|issue=7519|pages=481–483|doi=10.1038/513481a|pmid = 25254460|bibcode=2014Natur.513..481B|doi-access=free}}{{cite journal | vauthors = Dahlin JL, Walters MA | title = The essential roles of chemistry in high-throughput screening triage | journal = Future Medicinal Chemistry | volume = 6 | issue = 11 | pages = 1265–90 | date = July 2014 | pmid = 25163000 | pmc = 4465542 | doi = 10.4155/fmc.14.60 }}
=Alkaloids=
{{Further|Alkaloids}}
Alkaloids are bitter-tasting chemicals, widespread in nature, and often toxic. There are several classes with different modes of action as drugs, both recreational and pharmaceutical. Medicines of different classes include atropine, scopolamine, and hyoscyamine (all from nightshade),{{cite web |title=Atropa Belladonna |url=http://www.ema.europa.eu/docs/en_GB/document_library/Maximum_Residue_Limits_-_Report/2009/11/WC500010731.pdf |publisher=The European Agency for the Evaluation of Medicinal Products |access-date=26 February 2017 |date=1998 |archive-date=17 April 2018 |archive-url=https://web.archive.org/web/20180417200131/http://www.ema.europa.eu/docs/en_GB/document_library/Maximum_Residue_Limits_-_Report/2009/11/WC500010731.pdf |url-status=dead }} the traditional medicine berberine (from plants such as Berberis and Mahonia), caffeine (Coffea), cocaine (Coca), ephedrine (Ephedra), morphine (opium poppy), nicotine (tobacco), reserpine (Rauvolfia serpentina), quinidine and quinine (Cinchona), vincamine (Vinca minor), and vincristine (Catharanthus roseus).{{cite journal | last1 =Gremigni|display-authors=etal| first1=P.| year=2003| title =The interaction of phosphorus and potassium with seed alkaloid concentrations, yield and mineral content in narrow-leafed lupin (Lupinus angustifolius L.) | journal=Plant and Soil | volume=253| issue=2 | pages =413–427 | publisher=Springer | location=Heidelberg | jstor=24121197|doi=10.1023/A:1024828131581|bibcode=2003PlSoi.253..413G |s2cid=25434984}}
File:Opium poppy.jpg|The opium poppy Papaver somniferum is the source of the alkaloids morphine and codeine.
File:Nicotine.svg|The alkaloid nicotine from tobacco binds directly to the body's Nicotinic acetylcholine receptors, accounting for its pharmacological effects.{{cite web |title=Nicotinic acetylcholine receptors: Introduction |url=http://www.iuphar-db.org/DATABASE/FamilyIntroductionForward?familyId=76&familyType=IC |website=IUPHAR Database |publisher=International Union of Basic and Clinical Pharmacology |access-date=26 February 2017 |archive-date=29 June 2017 |archive-url=https://web.archive.org/web/20170629235725/http://www.iuphar-db.org/DATABASE/FamilyIntroductionForward?familyId=76&familyType=IC |url-status=dead }}
File:Koeh-018.jpg|Deadly nightshade, Atropa belladonna, yields tropane alkaloids including atropine, scopolamine and hyoscyamine.
File:DMT.svg|N,N-Dimethyltryptamine (DMT) a powerful psychedelic compound which is present in several plant species found across the globe, commonly found in Mimosa and Acacia species but has also been discovered in grasses such as Philaris Aquatica.
=Glycosides=
{{Further|Glycosides}}
Anthraquinone glycosides are found in senna,{{cite journal |author1=Hietala, P. |author2=Marvola, M. |author3=Parviainen, T. |author4=Lainonen, H. | title=Laxative potency and acute toxicity of some anthraquinone derivatives, senna extracts and fractions of senna extracts | volume=61 | issue=2 | pages=153–6 | journal=Pharmacology & Toxicology | pmid=3671329 |date=August 1987 | doi=10.1111/j.1600-0773.1987.tb01794.x }} rhubarb, and Aloe.{{cite book |title = Phytochemistry of Medicinal Plants |author1=John T. Arnason |author2=Rachel Mata |author3=John T. Romeo |date = 2013-11-11 |publisher = Springer Science & Business Media |isbn = 9781489917782 }}
The cardiac glycosides are phytochemicals from plants including foxglove and lily of the valley. They include digoxin and digitoxin which act as diuretics.{{cite web|title=Active Plant Ingredients Used for Medicinal Purposes |url=https://www.fs.fed.us/wildflowers/ethnobotany/medicinal/ingredients.shtml|publisher=United States Department of Agriculture|access-date=18 February 2017}}
File:Senna alexandrina Mill.-Cassia angustifolia L. (Senna Plant).jpg|Senna alexandrina, containing anthraquinone glycosides, has been used as a laxative for millennia.
Digitalis purpurea2.jpg|The foxglove, Digitalis purpurea, contains digoxin, a cardiac glycoside. The plant was used to treat heart conditions long before the glycoside was identified.{{cite web |title=Digitalis purpurea. Cardiac Glycoside |url=http://botany.csdl.tamu.edu/FLORA/Wilson/481/medbot/bot2.htm |publisher=Texas A&M University |access-date=26 February 2017 |quote=The man credited with the introduction of digitalis into the practice of medicine was William Withering. |archive-date=2 July 2018 |archive-url=https://web.archive.org/web/20180702064956/http://botany.csdl.tamu.edu/FLORA/Wilson/481/medbot/bot2.htm |url-status=dead }}
File:Digoxin.svg|Digoxin is used to treat atrial fibrillation, atrial flutter and sometimes heart failure.
=Polyphenols=
{{Further|Polyphenol}}
Polyphenols of several classes are widespread in plants, including anthocyanins, phytoestrogens, and tannins.{{cite web |title=Flavonoids |url=https://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids |publisher=Micronutrient Information Center, Linus Pauling Institute, Oregon State University |access-date=11 October 2023 |date=1 February 2016}} Polyphenols are secondary metabolites produced by almost every part of plants, including fruits, flowers, leaves and bark.
File:Angelica sylvestris 3.jpg|Angelica, containing phytoestrogens
File:Phytoestrogens2.png|Polyphenols include phytoestrogens (top and middle)
File:Figure 1 Chemical structures of the three main types of anthocyanins.jpg|Anthocyanins are a class of polyphenol that contributes to the color of many plants.
File:Tannic acid.svg|Tannic acids are one example of many complex polyphenolic structures produced by plants.
=Terpenes=
{{Further|Terpenes}}
Terpenes and terpenoids of many kinds are found in resinous plants such as the conifers. They are aromatic and serve to repel herbivores. Their scent makes them useful in essential oils, whether for perfumes such as rose and lavender, or for aromatherapy.{{cite journal | last1 = Tchen| first1 = T. T.| year = 1965| title = Reviewed Work: The Biosynthesis of Steroids, Terpenes & Acetogenins | journal = American Scientist | volume = 53| issue = 4 | pages = 499A–500A | publisher = Sigma Xi, The Scientific Research Society | location =Research Triangle Park, NC | jstor = 27836252}}{{cite journal | last1 = Singsaas| first1 = Eric L.| year = 2000 | title = Terpenes and the Thermotolerance of Photosynthesis | journal = New Phytologist | volume = 146| issue = 1 | pages = 1–2 | publisher = Wiley | location = New York | jstor = 2588737 | doi=10.1046/j.1469-8137.2000.00626.x| doi-access = free | bibcode = 2000NewPh.146....1S}} Some have had medicinal uses: thymol is an antiseptic and was once used as a vermifuge (anti-worm medicine).{{Cite journal|last=Roy|first=Kuhu|date=2015-09-01|title=Tinospora cordifolia stem supplementation in diabetic dyslipidemia: an open labelled randomized controlled trial|url=https://www.ffhdj.com/index.php/ffhd/article/view/208|journal=Functional Foods in Health and Disease|language=en|volume=5|issue=8|pages=265–274|doi=10.31989/ffhd.v5i8.208|issn=2160-3855|doi-access=free}}
File:Thymian.jpg|The essential oil of common thyme (Thymus vulgaris), contains the monoterpene thymol, an antiseptic and antifungal.{{cite web|title=Thymol (CID=6989)|url=https://pubchem.ncbi.nlm.nih.gov/compound/thymol|publisher=NIH|access-date=26 February 2017|quote=THYMOL is a phenol obtained from thyme oil or other volatile oils used as a stabilizer in pharmaceutical preparations, and as an antiseptic (antibacterial or antifungal) agent. It was formerly used as a vermifuge.}}
File:Thymol2.svg|Thymol is one of many terpenes found in plants.
File:Isoprene Structural Formulae V.1.svg|Terpenes are polymer of isoprene
Genetics
Contrary to bacteria and fungi, most plant metabolic pathways are not grouped into biosynthetic gene clusters, but instead are scattered as individual genes. Some exceptions have been discovered: steroidal glycoalkaloids in Solanum, polyketides in Pooideae, benzoxazinoids in Zea mays, triterpenes in Avena sativa, Cucurbitaceae, Arabidopsis, and momilactone diterpenes in Oryza sativa.{{cite journal | last1=Lacchini | first1=Elia | last2=Goossens | first2=Alain | title=Combinatorial Control of Plant Specialized Metabolism: Mechanisms, Functions, and Consequences | journal=Annual Review of Cell and Developmental Biology | publisher=Annual Reviews | volume=36 | issue=1 | date=2020-10-06 | issn=1081-0706 | doi=10.1146/annurev-cellbio-011620-031429 | pages=291–313| pmid=32559387 | s2cid=219947907 }}
References
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