''p''-Coumaric acid is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula HOC₆H₄CH=CHCO₂H. It is one of the three isomers of

coumaric acid Coumaric acid is a phenolic derivative of cinnamic acid having a hydroxy group as substituent at one of the aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of un ...

. It is a white solid that is only slightly soluble in water but very soluble in

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

and

diethyl ether Diethyl ether, or simply ether, is an organic compound with the chemical formula , sometimes abbreviated as . It is a colourless, highly Volatility (chemistry), volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It belongs ...

Natural occurrences

It is a precursor to many natural products, especially lignols, precursors to the woody mass that comprise many plants. Of the myriad occurrences, ''p''-coumaric acid can be found in ''

Gnetum cleistostachyum ''Gnetum cleistostachyum'' is a liana species in the ''Sessiles'' subsection of the genus ''Gnetum'' described from South East Yunnan. The name is still invalid and efloras states it is advisable to postpone validating it until more complete co ...

''.

In food

''p''-Coumaric acid can be found in a wide variety of edible plants and fungi such as

peanut The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), goober pea, pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics by small and large ...

navy bean The navy bean, haricot bean, Jigna bean, pearl haricot bean, Boston bean, white pea bean, or pea bean is a variety of the common bean (''Phaseolus vulgaris'') native to the Americas, where it was first domesticated. It is a dry white bean that ...

tomato The tomato (, ), ''Solanum lycopersicum'', is a plant whose fruit is an edible Berry (botany), berry that is eaten as a vegetable. The tomato is a member of the nightshade family that includes tobacco, potato, and chili peppers. It originate ...

es,

carrot The carrot ('' Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in colour, though heirloom variants including purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild ...

basil Basil (, ; , ; ''Ocimum basilicum'' (, )), also called great basil, is a culinary herb of the family Lamiaceae (mints). It is a hardiness (plants), tender plant, and is used in cuisines worldwide. In Western cuisine, the generic term "basil" r ...

and

garlic Garlic (''Allium sativum'') is a species of bulbous flowering plants in the genus '' Allium''. Its close relatives include the onion, shallot, leek, chives, Welsh onion, and Chinese onion. Garlic is native to central and south Asia, str ...

. It is found in

wine Wine is an alcoholic drink made from Fermentation in winemaking, fermented fruit. Yeast in winemaking, Yeast consumes the sugar in the fruit and converts it to ethanol and carbon dioxide, releasing heat in the process. Wine is most often made f ...

and

vinegar Vinegar () is an aqueous solution of diluted acetic acid and trace compounds that may include flavorings. Vinegar typically contains from 5% to 18% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting ...

. It is also found in

barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...

grain. ''p''-Coumaric acid from

pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...

is a constituent of

honey Honey is a sweet and viscous substance made by several species of bees, the best-known of which are honey bees. Honey is made and stored to nourish bee colonies. Bees produce honey by gathering and then refining the sugary secretions of pl ...

Derivatives

''p''-Coumaric acid glucoside can also be found in commercial

bread Bread is a baked food product made from water, flour, and often yeast. It is a staple food across the world, particularly in Europe and the Middle East. Throughout recorded history and around the world, it has been an important part of many cu ...

s containing

flaxseed Flax, also known as common flax or linseed, is a flowering plant, ''Linum usitatissimum'', in the family Linaceae. It is cultivated as a food and fiber crop in regions of the world with temperate climates. In 2022, France produced 75% of the ...

. Diesters of ''p''-coumaric acid can be found in

carnauba wax Carnauba (; ), also called Brazil wax and palm wax, is a wax of the leaves of the carnauba palm '' Copernicia prunifera'' (synonym: ''Copernicia cerifera''), a plant native to and grown only in the northeastern Brazilian states of Ceará, Piau ...

Biosynthesis

It is biosynthesized from

cinnamic acid Cinnamic acid is an organic compound with the formula phenyl, C6H5-CH=CH-Carboxylic acid, COOH. It is a white crystalline compound that is slightly soluble in water, and freely soluble in many organic solvents. Classified as an unsaturated carboxy ...

by the action of the

P450 Cytochromes P450 (P450s or CYPs) are a superfamily of enzymes containing heme as a cofactor that mostly, but not exclusively, function as monooxygenases. However, they are not omnipresent; for example, they have not been found in ''Escherichi ...

-dependent enzyme 4-cinnamic acid hydroxylase (C4H). :

\begin\\\xrightarrow\mathrm\\\end

It is also produced from L-

tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a conditionally essential amino acid with a polar side group. The word "tyrosine" is ...

by the action of tyrosine ammonia lyase (TAL). : L-Tyrosin - L-Tyrosine

\xrightarrow\mathrm

+ NH₃ + H⁺

Biosynthetic building block

''p''-Coumaric acid is the precursor of 4-ethylphenol produced by the

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...

Brettanomyces ''Brettanomyces'' is a non-spore forming genus of yeast in the family Saccharomycetaceae, and is often colloquially referred to as "Brett". The genus name ''Dekkera'' is used interchangeably with ''Brettanomyces'', as it describes the teleomor ...

'' in wine. The enzyme cinnamate decarboxylase catalyzes the conversion of ''p''-coumaric acid into 4-vinylphenol. Vinyl phenol reductase then catalyzes the reduction of 4-vinylphenol to 4-ethylphenol. Coumaric acid is sometimes added to

microbiological media Microbiology () is the scientific study of microorganisms, those being of unicellular (single-celled), multicellular (consisting of complex cells), or acellular (lacking cells). Microbiology encompasses numerous sub-disciplines including virol ...

, enabling the positive identification of ''Brettanomyces'' by smell. : Coumaric acid to 4-ethyphenol

''cis''-''p''-Coumarate glucosyltransferase is an enzyme that uses

uridine diphosphate glucose Uridine diphosphate glucose (uracil-diphosphate glucose, UDP-glucose) is a nucleotide sugar. It is involved in glycosyltransferase reactions in metabolism. Functions UDP-glucose is used in nucleotide sugar metabolism as an activated form of g ...

and ''cis''-''p''-coumarate to produce 4′-''O''-β-D-glucosyl-''cis''-''p''-coumarate and

uridine diphosphate Uridine diphosphate, abbreviated UDP, is an organic compound. It is an ester of pyrophosphoric acid with the nucleoside uridine. UDP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase uracil. UDP is an important fa ...

(UDP). This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases. Phloretic acid, found in the

rumen The rumen, also known as a paunch, is the largest stomach compartment in ruminants. The rumen and the reticulum make up the reticulorumen in ruminant animals. The diverse microbial communities in the rumen allows it to serve as the primary si ...

sheep Sheep (: sheep) or domestic sheep (''Ovis aries'') are a domesticated, ruminant mammal typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to d ...

fed with dried grass, is produced by hydrogenation of the 2-propenoic side chain of ''p''-coumaric acid. The enzyme, resveratrol synthase, also known as stilbene synthase, catalyzes the synthesis of

resveratrol Resveratrol (3,5,4′-trihydroxy-''trans''-stilbene) is a stilbenoid, a type of natural phenol or polyphenol and a phytoalexin produced by several plants in response to injury or when the plant is under attack by pathogens, such as bacterium, ba ...

ultimately from a tetraketide derived from 4-coumaroyl CoA. ''p''-Coumaric acid is a cofactor of photoactive yellow proteins (PYP), a homologous group of proteins found in many eubacteria. ''p''-Coumaric acid is found as the base moiety of

caleicine Caleicine is a unique sesquiterpene compound found exclusively in ''Calea ternifolia'', a Mexican flowering plant known for its potential psychoactive properties. This compound has garnered interest in the field of ethnopharmacology and natural ...

, one of many

sesquiterpenes Sesquiterpenes are a class of terpenes that consist of three isoprene units and often have the molecular formula C15H24. Like monoterpenes, sesquiterpenes may be cyclic or contain rings, including many combinations. Biochemical modifications s ...

in ''

Calea ternifolia ''Calea ternifolia'' ( syn. ''Calea zacatechichi'') is a species of flowering plant in the aster family, Asteraceae. It is native to Mexico and Central America. Its English language common names include bitter-grass, Mexican calea, and dream herb ...

.''

References