Phenylpropanoid
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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]]