Phenylpropanoid 4392867 218715579 2008-06-11T21:16:45Z NBonawitz 7290726 /* Cinnamic acids */ '''Phenylpropanoids''' are a class of plant-derived [[organic compound]]s that are biosynthesized from the [[amino acid]] [[phenylalanine]]. They have a wide variety of functions, including defense against [[herbivore]]s, microbial attack, or other sources of injury; as structural components of [[cell wall]]s; as protection from [[ultraviolet light]]; as [[pigment]]s; and as [[signaling molecule]]s. ==Cinnamic acids== [[Image:Cinnamic acid.svg|thumb|right|150px|Cinnamic acid]] Phenylalanine is first converted to [[cinnamic acid]] by the action of the [[enzyme]] [[phenylalanine ammonia-lyase]] (PAL). A series of enzymatic [[hydroxylation]]s and [[methylation]]s leads to [[coumaric acid]], [[caffeic acid]], [[ferulic acid]], [[5-hydroxyferulic acid]], and [[sinapic acid]]. Conversion of these acids to their corresponding [[ester]]s produces some of the volatile components of herb and flower [[fragrance]]s which serve many functions such as attracting [[pollinator]]s. [[Ethyl cinnamate]] is a common example. ==Cinnamic aldehydes and monolignols== [[Image:Coniferyl alcohol.png|thumb|right|150px|Coniferyl alcohol]] Reduction of the [[carboxylic acid]] functional groups in the cinnamic acids provides the corresponding aldehydes, such as [[cinnamaldehyde]]. Further reduction provides [[monolignol]]s including [[coumaryl alcohol]], [[coniferyl alcohol]], and [[sinapyl alcohol]]. The monolignols are monomers that are [[polymer]]ized to generate various forms of [[lignin]] and [[suberin]], which are used as a structural component of plant cell walls. [[Image:Safrole acsv.svg|thumb|right|150px|Safrole]] The phenylpropenes, including [[eugenol]], [[chavicol]], [[safrole]] and [[estragole]], are also derived from the monolignols. The compounds are the primary constituents of various [[essential oil]]s. ==Coumarins and flavonoids== [[Image:Umbelliferone acsv.svg|thumb|right|150px|Umbelliferone]] Hydroxylation of [[cinnamic acid]] in the 4-position leads to [[coumaric acid|''p''-coumaric acid]], which can be further modified into hydroxylated derivatives such as [[umbelliferone]]. Another use of ''p''-coumaric acid via its [[thioester]] with [[coenzyme A]], i.e. 4-coumaroyl-CoA, is the production of [[chalcone]]. This is achieved with the addition of 3 [[malonyl-CoA]] molecules and their cyclization into a second [[phenyl]] group ''(see [[polyphenols]])''. Chalcone is the precursor of all [[flavonoid]]s, a diverse class of [[phytochemical]]s. ==Stilbenoids== [[Image:resveratrol.svg|thumb|150px|''trans''-resveratrol]] [[Stilbenoid]]s, such as [[resveratrol]], are hydroxylated derivatives of [[stilbene]]. They are formed through an alternative cyclization of cinammoyl-CoA or 4-coumaroyl-CoA. ==References== *{{cite journal | author = K Hahlbrock, D Scheel | title = Physiology and Molecular Biology of Phenylpropanoid Metabolism | journal = Annual Review of Plant Physiology and Plant Molecular Biology | year = 1989 | volume = 40 | issue = | pages = 347–69 | url = http://arjournals.annualreviews.org/doi/pdf/10.1146/annurev.pp.40.060189.002023 | doi = 10.1146/annurev.pp.40.060189.002023}} {{Phenylpropanoids}} {{flavonoids}} [[Category:Phytochemicals]] [[Category:Phenylpropanoids|*]] [[bg:Фенилпропаноид]] [[de:Phenylpropane]] [[nl:Fenylpropanoïde]] [[ja:フェニルプロパノイド]]