Naturally occurring phenols

Various classification schemes can be applied.{{Cite book |last1=Vermerris |first1=Wilfred |url=https://books.google.com/books?id=uLzdv8fsRxYC |title=Phenolic Compound Biochemistry |last2=Nicholson |first2=Ralph |date=2007-02-20 |publisher=Springer Science & Business Media |isbn=9781402051647}}{{rp|2}} A commonly used scheme is based on the number of carbons and was devised by Jeffrey Harborne and Simmonds in 1964 and published in 1980:{{rp|2}}{{cite book |last1=Harborne |first1=J. B. |year=1980 |chapter=Plant phenolics |editor1-last=Bell |editor1-first=E. A. |editor2-last=Charlwood |editor2-first=B. V. |url=https://cir.nii.ac.jp/crid/1573105974946965376 |title=Encyclopedia of Plant Physiology, Volume 8: Secondary Plant Products |publisher=Springer-Verlag |location=Berlin Heidelberg New York |pages=329–395}}{{Citation |last=Lattanzio |first=Vincenzo |title=Phenolic Compounds: Introduction |date=January 2013 |url=https://doi.org/10.1007/978-3-642-22144-6_57 |work=Natural Products: Phytochemistry, Botany and Metabolism of Alkaloids, Phenolics and Terpenes |pages=1543–1580 |editor-last=Ramawat |editor-first=Kishan Gopal |place=Berlin, Heidelberg |publisher=Springer |language=en |doi=10.1007/978-3-642-22144-6_57 |isbn=9783642221446 |editor2-last=Mérillon |editor2-first=Jean-Michel}}

C₆-C₇-C₆ Diarylheptanoids are not included in this Harborne classification.

They can also be classified on the basis of their number of phenol groups. They can therefore be called simple phenols or monophenols, with only one phenolic group, or di- (bi-), tri- and oligophenols, with two, three or several phenolic groups respectively.

A diverse family natural phenols are the flavonoids, which include several thousand compounds, among them the flavonols, flavones, flavan-3ol (catechins), flavanones, anthocyanidins, and isoflavonoids.{{cite book |title=Clinical Guide to Nutrition and Dietary Supplements in Disease Management |url=https://books.google.com/books?id=MyFtAAAAMAAJ |first=Jennifer R. |last=Jamison |isbn=9780443071935 |page=525 |year=2003 | publisher=Churchill Livingstone }}

The phenolic unit can be found dimerized or further polymerized, creating a new class of polyphenol. For example, ellagic acid is a dimer of gallic acid and forms the class of ellagitannins, or a catechin and a gallocatechin can combine to form the red compound theaflavin, a process that also results in the large class of brown thearubigins in tea.

Two natural phenols from two different categories, for instance a flavonoid and a lignan, can combine to form a hybrid class like the flavonolignans.

Nomenclature of polymers:

Plants in the genus Humulus and Cannabis produce terpenophenolic metabolites, compounds that are meroterpenes.Chapter eight: "Biosynthesis of terpenophenolic metabolites in hop and cannabis". Jonathan E. Page and Jana Nagel, Recent Advances in Phytochemistry, 2006, Volume 40, pp. 179–210, {{doi|10.1016/S0079-9920(06)80042-0}}{{cite book |last1=Page |first1=Jonathan E. |last2=Nagel |first2=Jana |chapter=Chapter Eight - Biosynthesis of Terpenophenolic Metabolites in Hop and Cannabis |date=January 2006 |chapter-url=https://www.sciencedirect.com/science/article/pii/S0079992006800420 |title=Recent Advances in Phytochemistry |volume=40 |pages=179–210 |editor-last=Romeo |editor-first=John T. |series=Integrative Plant Biochemistry |publisher=Elsevier|doi=10.1016/S0079-9920(06)80042-0 |isbn=9780080451251 }} Phenolic lipids are long aliphatic chains bonded to a phenolic moiety.

Many natural phenols are chiral. An example of such molecules is catechin. Cavicularin is an unusual macrocycle because it was the first compound isolated from nature displaying optical activity due to the presence of planar chirality and axial chirality.

Natural phenols show optical properties characteristic of benzene, e.g. absorption near 270 nm. According to Woodward's rules, bathochromic shifts often also happen suggesting the presence of delocalised π electrons arising from a conjugation between the benzene and vinyls groups.{{cite journal | doi = 10.1016/j.chroma.2006.01.060 | title = Rapid analysis of stilbenes and derivatives from downy mildew-infected grapevine leaves by liquid chromatography–atmospheric pressure photoionisation mass spectrometry | year = 2006 | last1 = Jeandenis | first1 = J. | last2 = Pezet | first2 = R. | last3 = Tabacchi | first3 = R. | journal = Journal of Chromatography A | volume = 1112 | pages = 263–8 | pmid = 16458906 | issue = 1–2 }}

As molecules with higher conjugation levels undergo this bathochromic shift phenomenon, a part of the visible spectrum is absorbed. The wavelengths left in the process (generally in red section of the spectrum) recompose the color of the particular substance. Acylation with cinnamic acids of anthocyanidins shifted color tonality (CIE Lab hue angle) to purple.{{Cite journal | last1 = Stintzing | first1 = F. C. | last2 = Stintzing | first2 = A. S. | last3 = Carle | first3 = R. | last4 = Frei | first4 = B. | last5 = Wrolstad | first5 = R. E. |url=https://pubmed.ncbi.nlm.nih.gov/12358498/ | title = Color and Antioxidant Properties of Cyanidin-Based Anthocyanin Pigments | doi = 10.1021/jf0204811 | journal = Journal of Agricultural and Food Chemistry | volume = 50 | issue = 21 | pages = 6172–6181 | year = 2002 | pmid = 12358498| bibcode = 2002JAFC...50.6172S }}

Here is a series of UV visible spectra of molecules classified from left to right according to their conjugation level:{{citation needed|date=July 2024}}

The absorbance pattern responsible for the red color of anthocyanins may be complementary to that of green chlorophyll in photosynthetically active tissues such as young Quercus coccifera leaves.{{Cite journal | last1 = Karageorgou | first1 = P. | last2 = Manetas | first2 = Y. | doi = 10.1093/treephys/26.5.613 | title = The importance of being red when young: Anthocyanins and the protection of young leaves of Quercus coccifera from insect herbivory and excess light | journal = Tree Physiology | volume = 26 | issue = 5 | pages = 613–621 | year = 2006 | pmid = 16452075| doi-access = free }}

File:Oxydation du dimere B2.PNG dimer. New peaks have appeared in the oxidised sample.]]

Natural phenols are reactive species toward oxidation, notably the complex mixture of phenolics, found in food for example, can undergo autoxidation during the ageing process. Simple natural phenols can lead to the formation of B type proanthocyanidins in wines{{Cite journal |last1=Sun |first1=Weixing |last2=Miller |first2=Jack M. |date=2003 |title= Tandem mass spectrometry of the B-type procyanidins in wine and B-type dehydrodicatechins in an autoxidation mixture of (+)-catechin and (−)-epicatechin|url=https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=14708334 |journal= Journal of Mass Spectrometry|volume=38 |issue=4 |pages=438–446 |doi=10.1002/jms.456 |pmid=12717756 |bibcode=2003JMSp...38..438S |issn=1076-5174}} or in model solutions.{{Cite journal | last1 = He | first1 = F. | last2 = Pan | first2 = Q. H. | last3 = Shi | first3 = Y. | last4 = Zhang | first4 = X. T. | last5 = Duan | first5 = C. Q. | title = Identification of autoxidation oligomers of flavan-3-ols in model solutions by HPLC-MS/MS | doi = 10.1002/jms.1536 | journal = Journal of Mass Spectrometry | volume = 44 | issue = 5 | pages = 633–640 | year = 2009 | pmid = 19053150| bibcode = 2009JMSp...44..633H | doi-access = free }}{{Cite journal | last1 = Cilliers | first1 = J. J. L. | last2 = Singleton | first2 = V. L. | doi = 10.1021/jf00088a013 |url=https://pubs.acs.org/doi/pdf/10.1021/jf00088a013 | title = Nonenzymic autoxidative phenolic browning reactions in a caffeic acid model system | journal = Journal of Agricultural and Food Chemistry | volume = 37 | issue = 4 | pages = 890–896 | year = 1989 | bibcode = 1989JAFC...37..890C }} This is correlated to the non-enzymatic browning color change characteristic of this process.{{cite journal|title=Nonenzymic Autoxidative Reactions of Caffeic Acid in Wine |first1=Johannes J. L. |last1=Cilliers |first2=Vernon L. |last2=Singleton |url=https://www.ajevonline.org/content/41/1/84 |journal=American Journal of Enology and Viticulture |year=1990 |volume=41 |issue=1 |pages=84–86|doi=10.5344/ajev.1990.41.1.84 |s2cid=83665714 }} This phenomenon can be observed in foods like carrot purees.{{Cite journal | last1 = Talcott | first1 = S. T. | last2 = Howard | first2 = L. R. | doi = 10.1021/jf981134n | title = Phenolic Autoxidation is Responsible for Color Degradation in Processed Carrot Puree | journal = Journal of Agricultural and Food Chemistry | volume = 47 | issue = 5 | pages = 2109–2115 | year = 1999 | pmid = 10552504| bibcode = 1999JAFC...47.2109T }}

Browning associated with oxidation of phenolic compounds has also been given as the cause of cells death in calli formed in in vitro cultures. Those phenolics originate both from explant tissues and from explant secretions.

{{further|Category:Phenols}}

{{main|Flavonoid biosynthesis|Phenylpropanoid biosynthesis}}

Phenolics are formed by three different biosynthetic pathways: (i) the shikimate/chorizmate or succinylbenzoate pathway, which produces the phenyl propanoid derivatives (C6–C3); (ii) the acetate/malonate or polyketide pathway, which produces the side-chain-elongated phenyl propanoids, including the large group of flavonoids (C6–C3–C6) and some quinones; and (iii) the acetate/mevalonate pathway, which produces the aromatic terpenoids, mostly monoterpenes, by dehydrogenation reactions.{{cite journal |last1=Knaggs |first1=Andrew R. |title=The biosynthesis of shikimate metabolites (1999) |journal=Natural Product Reports |volume=18 |issue=3 |pages=334–55 |year=2001 |pmid=11476485 |doi=10.1039/b001717p}} The aromatic amino acid phenylalanine, synthesized in the shikimic acid pathway, is the common precursor of phenol containing amino acids and phenolic compounds.

In plants, the phenolic units are esterified or methylated and are submitted to conjugation, which means that the natural phenols are mostly found in the glycoside form instead of the aglycone form.

In olive oil, tyrosol forms esters with fatty acids.{{cite journal |last1=Lucas |first1=Ricardo |last2=Comelles |first2=Francisco |last3=Alcántara |first3=David |last4=Maldonado |first4=Olivia S. |last5=Curcuroze |first5=Melanie |last6=Parra |first6=Jose L. |last7=Morales |first7=Juan C. |title=Surface-Active Properties of Lipophilic Antioxidants Tyrosol and Hydroxytyrosol Fatty Acid Esters: A Potential Explanation for the Nonlinear Hypothesis of the Antioxidant Activity in Oil-in-Water Emulsions |journal=Journal of Agricultural and Food Chemistry |volume=58 |issue=13 |pages=8021–6 |year=2010 |pmid=20524658 |doi=10.1021/jf1009928|bibcode=2010JAFC...58.8021L |hdl=11441/154173 |hdl-access=free }} In rye, alkylresorcinols are phenolic lipids.

Some acetylations involve terpenes like geraniol.{{cite journal |last1=Šmejkal |first1=Karel |last2=Grycová |first2=Lenka |last3=Marek |first3=Radek |last4=Lemière |first4=Filip |last5=Jankovská |first5=Dagmar |last6=Forejtníková |first6=Hana |last7=Vančo |first7=Ján |last8=Suchý |first8=Václav |title=C-Geranyl Compounds from Paulownia tomentosa Fruits |journal=Journal of Natural Products |volume=70 |issue=8 |pages=1244–8 |year=2007 |pmid=17625893 |doi=10.1021/np070063w|bibcode=2007JNAtP..70.1244S }} Those molecules are called meroterpenes (a chemical compound having a partial terpenoid structure).

Methylations can occur by the formation of an ether bond on hydroxyl groups forming O-methylated polyphenols. In the case of the O-methylated flavone tangeritin, all of the five hydroxyls are methylated, leaving no free hydroxyls of the phenol group. Methylations can also occur on directly on a carbon of the benzene ring like in the case of poriol, a C-methylated flavonoid.

The white rot fungus Phanerochaete chrysosporium can remove up to 80% of phenolic compounds from coking waste water.{{cite journal| title=Biodegradation of phenolic compounds from coking wastewater by immobilized white rot fungus Phanerochaete chrysosporium|author1=Lu Y|author2= Yan L|author3= Wang Y|author4= Zhou S|author5=Fu J|author6=Zhang J|journal=Journal of Hazardous Materials|date=June 2009|volume=165|issue=1–3|pages=1091–7|pmid=19062164|doi=10.1016/j.jhazmat.2008.10.091|bibcode=2009JHzM..165.1091L }}

Tannins are used in the tanning industry.

Some natural phenols have been proposed as biopesticides. Furanoflavonoids like karanjin or rotenoids are used as acaricide or insecticide.{{cite journal|last1=Perumalsamy|first1=Haribalan|last2=Jang|first2=Myung Jin|last3=Kim|first3=Jun-Ran|last4=Kadarkarai|first4=Murugan|last5=Ahn|first5=Young-Joon|title=Larvicidal activity and possible mode of action of four flavonoids and two fatty acids identified in Millettia pinnata seed toward three mosquito species|journal=Parasites & Vectors|volume=8|issue=1|pages=237|year=2015|issn=1756-3305|doi=10.1186/s13071-015-0848-8|pmc=4410478|pmid=25928224 |doi-access=free }}

Some phenols are sold as dietary supplements. Phenols have been investigated as drugs. For instance, Crofelemer (USAN trade name Fulyzaq) is a drug under development for the treatment of diarrhea associated with anti-HIV drugs. Additionally, derivatives have been made of phenolic compound, combretastatin A-4, an anticancer molecule, including nitrogen or halogens atoms to increase the efficacy of the treatment.{{cite journal | last1 = Carr | first1 = Miriam | last2 = Greene | first2 = Lisa M. | last3 = Knox | first3 = Andrew J.S. | last4 = Lloyd | first4 = David G. | last5 = Zisterer | first5 = Daniela M. | last6 = Meegan | first6 = Mary J. | year = 2010 | title = Lead identification of conformationally restricted β-lactam type combretastatin analogues: Synthesis, antiproliferative activity and tubulin targeting effects | journal = European Journal of Medicinal Chemistry | volume = 45 | issue = 12| pages = 5752–5766 | doi = 10.1016/j.ejmech.2010.09.033 | pmid = 20933304 }}

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The recovery of natural phenols from biomass residue is part of biorefining.{{Cite journal | last1 = Villaverde | first1 = J. J. | last2 = De Vega | first2 = A. | last3 = Ligero | first3 = P. | last4 = Freire | first4 = C. S. R. | last5 = Neto | first5 = C. P. | last6 = Silvestre | first6 = A. J. D. | doi = 10.1021/jf101174x | title = Miscanthus x giganteus Bark Organosolv Fractionation: Fate of Lipophilic Components and Formation of Valuable Phenolic Byproducts | journal = Journal of Agricultural and Food Chemistry | volume = 58 | issue = 14 | pages = 8279–8285 | year = 2010 | pmid = 20593898| bibcode = 2010JAFC...58.8279V }}

Studies on evaluating antioxidant capacity can use electrochemical methods.{{cite journal | doi = 10.1021/ac101854w | title = How Do Phenolic Compounds React toward Superoxide Ion? A Simple Electrochemical Method for Evaluating Antioxidant Capacity | year = 2010 | last1 = René | first1 = Alice | last2 = Abasq | first2 = Marie-Laurence | last3 = Hauchard | first3 = Didier | last4 = Hapiot | first4 = Philippe | journal = Analytical Chemistry | volume = 82 | issue = 20 | pages = 8703–10 | pmid = 20866027 }}

Detection can be made by recombinant luminescent bacterial sensors.{{cite journal | doi = 10.1016/j.chemosphere.2006.01.026 | title = Analysis of bioavailable phenols from natural samples by recombinant luminescent bacterial sensors | year = 2006 | last1 = Leedjarv | first1 = A. | last2 = Ivask | first2 = A. | last3 = Virta | first3 = M. | last4 = Kahru | first4 = A. | journal = Chemosphere | volume = 64 | issue = 11 | pages = 1910–9 | pmid = 16581105 | bibcode = 2006Chmsp..64.1910L }}

Phenolic profiling can be achieved with liquid chromatography–mass spectrometry (LC/MS).{{Cite journal | last1 = Stobiecki | first1 = M. | last2 = Skirycz | first2 = A. | last3 = Kerhoas | first3 = L. | last4 = Kachlicki | first4 = P. | last5 = Muth | first5 = D. | last6 = Einhorn | first6 = J. | last7 = Mueller-Roeber | first7 = B. | doi = 10.1007/s11306-006-0031-5 | title = Profiling of phenolic glycosidic conjugates in leaves of Arabidopsis thaliana using LC/MS | journal = Metabolomics | volume = 2 | issue = 4 | pages = 197–219 | year = 2006 | s2cid = 39140266 }}

A method for phenolic content quantification is volumetric titration. An oxidizing agent, permanganate, is used to oxidize known concentrations of a standard solution, producing a standard curve. The content of the unknown phenols is then expressed as equivalents of the appropriate standard.

Some methods for quantification of total phenolic content are based on colorimetric measurements. Total phenols (or antioxidant effect) can be measured using the Folin-Ciocalteu reaction. Results are typically expressed as gallic acid equivalents (GAE). Ferric chloride (FeCl₃) test is also a colorimetric assay.

Lamaison and Carnet have designed a test for the determination of the total flavonoid content of a sample (AlCI₃ method). After proper mixing of the sample and the reagent, the mixture is incubated for 10 minutes at ambient temperature and the absorbance of the solution is read at 440 nm. Flavonoid content is expressed in mg/g of quercetin."Teneurs en principaux flavonoides des fleurs de Cratageus monogyna Jacq et de Cratageus Laevigata (Poiret D.C.) en Fonction de la vegetation". J. L. Lamaison and A. Carnet, Plantes Medicinales Phytotherapie, 1991, XXV, pages 12–16

Quantitation results produced by the means of diode array detector-coupled HPLC are generally given as relative rather than absolute values as there is a lack of commercially available standards for every phenolic molecules. The technique can also be coupled with mass spectrometry (for example, HPLC–DAD–ESI/MS) for more precise molecule identification.

; In vitro measurements

Other tests measure the antioxidant capacity of a fraction. Some make use of the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation, which is reactive towards most antioxidants including phenolics, thiols and vitamin C.{{cite journal |last1=Walker |first1=Richard B. |last2=Everette |first2=Jace D. |title=Comparative Reaction Rates of Various Antioxidants with ABTS Radical Cation |journal=Journal of Agricultural and Food Chemistry |volume=57 |issue=4 |pages=1156–61 |year=2009 |pmid=19199590 |doi=10.1021/jf8026765|bibcode=2009JAFC...57.1156W }} During this reaction, the blue ABTS radical cation is converted back to its colorless neutral form. The reaction may be monitored spectrophotometrically. This assay is often referred to as the Trolox equivalent antioxidant capacity (TEAC) assay. The reactivity of the various antioxidants tested are compared to that of Trolox, which is a vitamin E analog.

Other antioxidant capacity assays that use Trolox as a standard include the diphenylpicrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC), ferric reducing ability of plasma (FRAP) assays or inhibition of copper-catalyzed in vitro human low-density lipoprotein oxidation.{{cite journal | doi = 10.1021/jf960721a | title = Inhibition of Human Low-Density Lipoprotein Oxidation in Relation to Composition of Phenolic Antioxidants in Grapes (Vitis vinifera) | year = 1997 | last1 = Meyer | first1 = Anne S. | last2 = Yi | first2 = Ock-Sook | last3 = Pearson | first3 = Debra A. | last4 = Waterhouse | first4 = Andrew L. | last5 = Frankel | first5 = Edwin N. | journal = Journal of Agricultural and Food Chemistry | volume = 45 | issue = 5 | pages = 1638–1643 | bibcode = 1997JAFC...45.1638M }}

A cellular antioxidant activity (CAA) assay also exists. Dichlorofluorescin is a probe that is trapped within cells and is easily oxidized to fluorescent dichlorofluorescein (DCF). The method measures the ability of compounds to prevent the formation of DCF by 2,2'-Azobis(2-amidinopropane) dihydrochloride (ABAP)-generated peroxyl radicals in human hepatocarcinoma HepG2 cells.{{Cite journal | last1 = Wolfe | first1 = K. L. | last2 = Liu | first2 = R. H. | doi = 10.1021/jf0715166 | title = Cellular Antioxidant Activity (CAA) Assay for Assessing Antioxidants, Foods, and Dietary Supplements | journal = Journal of Agricultural and Food Chemistry | volume = 55 | issue = 22 | pages = 8896–8907 | year = 2007 | pmid = 17902627| bibcode = 2007JAFC...55.8896W }}

Other methods include butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), Rancimat method (rancidification assessment of fat).{{cite journal | last1 = Astrid | last2 = von Gadow | first2 = Elizabeth Joubert | last3 = Hansmann | first3 = Chris F. | year = 1997 | title = Comparison of the Antioxidant Activity of Aspalathin with That of Other Plant Phenols of Rooibos Tea (Aspalathus linearis), α-Tocopherol, BHT, and BHA | journal = J. Agric. Food Chem. | volume = 45 | issue = 3| pages = 632–638 | doi = 10.1021/jf960281n | bibcode = 1997JAFC...45..632V }}

; In vivo models

Larvae of the model animal Galleria mellonella, also called waxworms, can be used to test the antioxidant effect of individual molecules using boric acid in food to induce an oxidative stress.{{cite journal | last1 = Hyršl | first1 = Pavel | last2 = Büyükgüzel | first2 = Ender | last3 = Büyükgüzel | first3 = Kemal | year = 2007 | title = The effects of boric acid-induced oxidative stress on antioxidant enzymes and survivorship in Galleria mellonella | journal = Archives of Insect Biochemistry and Physiology | volume = 66 | issue = 1| pages = 23–31 | doi = 10.1002/arch.20194|pmid=17694562 }} The content of malondialdehyde, an oxidative stress indicator, and activities of the antioxidant enzymes superoxide dismutase, catalase, glutathione S-transferase and glutathione peroxidase can be monitored. A prophenoloxidase can also be recovered from the insect.{{cite journal | last1 = Kopácek | first1 = Petr | last2 = Weise | first2 = Christoph | last3 = Götz | first3 = Peter | year = 1995 | title = The prophenoloxidase from the wax moth Galleria mellonella: purification and characterization of the proenzyme | journal = Insect Biochemistry and Molecular Biology | volume = 25 | issue = 10| pages = 1081–1091 | doi = 10.1016/0965-1748(95)00040-2 | pmid = 8580908 | bibcode = 1995IBMB...25.1081K }}

The phenolic biosynthetic and metabolic pathways and enzymes can be studied by means of transgenesis of genes. The Arabidopsis regulatory gene for production of Anthocyanin Pigment 1 (AtPAP1) can be expressed in other plant species.{{cite journal | doi = 10.1021/jf903527y | title = Purple Canola: ArabidopsisPAP1Increases Antioxidants and Phenolics in Brassica napus Leaves | year = 2010 | last1 = Li | first1 = Xiang | last2 = Gao | first2 = Ming-Jun | last3 = Pan | first3 = Hong-Yu | last4 = Cui | first4 = De-Jun | last5 = Gruber | first5 = Margaret Y. | journal = Journal of Agricultural and Food Chemistry | volume = 58 | issue = 3 | pages = 1639–45 | pmid = 20073469 | bibcode = 2010JAFC...58.1639L }}

Phenols are found in the natural world, especially in the plant kingdom.

Orobol can be found in Streptomyces neyagawaensis (an Actinobacterium).{{citation needed|date=March 2013}} Phenolic compounds can be found in the cyanobacterium Arthrospira maxima, used in the dietary supplement, Spirulina.Production of phenolic compounds by Spirulina maxima microalgae and their protective effects in vitro toward hepatotoxicity model. Abd El-Baky Hanaa H., El Baz Farouk K. and El-Baroty Gamal S., Advances in food sciences, 2009, volume 31, number 1, pp. 8–16, {{INIST|21511068}} The three cyanobacteria Microcystis aeruginosa, Cylindrospermopsis raciborskii and Oscillatoria sp. are the subject of research into the natural production of butylated hydroxytoluene (BHT), an antioxidant, food additive and industrial chemical.

The proteobacterium Pseudomonas fluorescens produces phloroglucinol, phloroglucinol carboxylic acid and diacetylphloroglucinol.{{cite journal | last1 = Achkar | first1 = Jihane | last2 = Xian | first2 = Mo | last3 = Zhao | first3 = Huimin | last4 = Frost | first4 = J. W. | year = 2005 | title = Biosynthesis of Phloroglucinol | journal = J. Am. Chem. Soc. | volume = 127 | issue = 15| pages = 5332–5333 | doi = 10.1021/ja042340g | pmid=15826166| bibcode = 2005JAChS.127.5332A }} Another example of phenolics produced in proteobacteria is 3,5-dihydroxy-4-isopropyl-trans-stilbene, a bacterial stilbenoid produced in Photorhabdus bacterial symbionts of Heterorhabditis nematodes.

Phenolic acids can be found in mushroom basidiomycetes species.{{cite journal | doi = 10.1016/j.fct.2009.01.039 | title = Phenolic acids determination by HPLC–DAD–ESI/MS in sixteen different Portuguese wild mushrooms species | year = 2009 | last1 = Barros | first1 = Lillian | last2 = Dueñas | first2 = Montserrat | last3 = Ferreira | first3 = Isabel C.F.R. | last4 = Baptista | first4 = Paula | last5 = Santos-Buelga | first5 = Celestino | journal = Food and Chemical Toxicology | volume = 47 | issue = 6 | pages = 1076–9 | pmid = 19425182 }} For example, protocatechuic acid and pyrocatechol are found in Agaricus bisporus{{cite journal |last1=Delsignore |first1=A |last2=Romeo |first2=F |last3=Giaccio |first3=M |title=Content of phenolic substances in basidiomycetes |journal=Mycological Research |volume=101 |pages=552–6 |year=1997 |doi=10.1017/S0953756296003206 |issue=5}} as well as other phenylated substances like phenylacetic and phenylpyruvic acids. Other compounds like atromentin and thelephoric acid can also be isolated from fungi in the Agaricomycetes class. Orobol, an isoflavone, can be isolated from Aspergillus niger.

; In yeasts

Aromatic alcohols (example: tyrosol) are produced by the yeast Candida albicans.{{cite journal | last1 = Ghosh | first1 = Suman | last2 = Kebaara | first2 = Bessie W. | last3 = Atkin | first3 = Audrey L. | last4 = Nickerson | first4 = Kenneth W. | year = 2008 | title = Regulation of Aromatic Alcohol Production in Candida albicans | journal = Applied and Environmental Microbiology | volume = 74 | issue = 23| pages = 7211–7218 | doi = 10.1128/AEM.01614-08 | pmid = 18836025 | pmc = 2592902 | bibcode = 2008ApEnM..74.7211G }} They are also found in beer.{{cite journal | last1 = Szlavko | first1 = Clara M. | year = 1973 | title = Trtptophol, tyrosol and phenylethanol—The aromatic ahigher alcohols in beer | journal = Journal of the Institute of Brewing | volume = 79 | issue = 4| pages = 283–288 | doi = 10.1002/j.2050-0416.1973.tb03541.x | doi-access = free }} These molecules are quorum sensing compounds for Saccharomyces cerevisiae.{{cite journal | last1 = Hogan | first1 = Deborah A. | year = 2006 | title = Quorum Sensing: Alcohols in a Social Situation | journal = Current Biology | volume = 16 | issue = 12| pages = R457–R458 | doi = 10.1016/j.cub.2006.05.035 | pmid=16782000| s2cid = 3970864 | doi-access = free | bibcode = 2006CBio...16.R457H }}

; Metabolism

Aryl-alcohol dehydrogenase uses an aromatic alcohol and NAD⁺ to produce an aromatic aldehyde, NADH and H⁺.

Aryl-alcohol dehydrogenase (NADP+) uses an aromatic alcohol and NADP⁺ to produce an aromatic aldehyde, NADPH and H⁺.

Aryldialkylphosphatase (also known as organophosphorus hydrolase, phosphotriesterase, and paraoxon hydrolase) uses an aryl dialkyl phosphate and H₂O to produce dialkyl phosphate and an aryl alcohol.

Gyrophoric acid, a depside, and orcinol are found in lichen.{{cite journal | author = Robiquet | year = 1829 | title = Essai analytique des lichens de l'orseille | journal = Annales de chimie et de physique | volume = 42 | pages = 236–257 }}

The green alga Botryococcus braunii is the subject of research into the natural production of butylated hydroxytoluene (BHT),{{cite journal |author1=Babu B. |author2=Wu J. T. |title=Production of Natural Butylated Hydroxytoluene as an Antioxidant by Freshwater Phytoplankton |journal=Journal of Phycology |volume=44 |issue=6 |pages=1447–1454 |date=December 2008 |url=http://ntur.lib.ntu.edu.tw/bitstream/246246/162863/1/22.pdf |doi=10.1111/j.1529-8817.2008.00596.x |pmid=27039859|bibcode=2008JPcgy..44.1447B |s2cid=26084768 }} an antioxidant, food additive and industrial chemical.

Phenolic acids such as protocatechuic, p-hydroxybenzoic, 2,3-dihydroxybenzoic, chlorogenic, vanillic, caffeic, p-coumaric and salicylic acid, cinnamic acid and hydroxybenzaldehydes such as p-hydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde, vanillin have been isolated from in vitro culture of the freshwater green alga Spongiochloris spongiosa.{{Cite journal | last1 = Onofrejová | first1 = L. | last2 = Vašíčková | first2 = J. | last3 = Klejdus | first3 = B. | last4 = Stratil | first4 = P. | last5 = Mišurcová | first5 = L. | last6 = Kráčmar | first6 = S. | last7 = Kopecký | first7 = J. | last8 = Vacek | first8 = J. | doi = 10.1016/j.jpba.2009.03.027 | title = Bioactive phenols in algae: The application of pressurized-liquid and solid-phase extraction techniques | journal = Journal of Pharmaceutical and Biomedical Analysis | volume = 51 | issue = 2 | pages = 464–470 | year = 2010 | pmid = 19410410}}

Phlorotannins, for instance eckol, are found in brown algae. Vidalenolone can be found in the tropical red alga Vidalia sp.{{Cite journal

| last1 = Yoo | first1 = H. D.

| last2 = Ketchum | first2 = S. O.

| last3 = France | first3 = D.

| last4 = Bair | first4 = K.

| last5 = Gerwick | first5 = W. H.

| title = Vidalenolone, a Novel Phenolic Metabolite from the Tropical Red AlgaVidaliasp

| doi = 10.1021/np010319c

| journal = Journal of Natural Products

| volume = 65

| issue = 1

| pages = 51–53

| year = 2002

| pmid = 11809064

| bibcode = 2002JNAtP..65...51Y

}}

Phenolic compounds are mostly found in vascular plants (tracheophytes) i.e. Lycopodiophyta{{Cite journal | last1 = Pedersen | first1 = J. A. | last2 = Øllgaard | first2 = B. | doi = 10.1016/0305-1978(82)90044-8 | title = Phenolic acids in the genus Lycopodium | journal = Biochemical Systematics and Ecology | volume = 10 | pages = 3–9 | year = 1982 | issue = 1 | bibcode = 1982BioSE..10....3P }} (lycopods), Pteridophyta (ferns and horsetails), Angiosperms (flowering plants or Magnoliophyta) and Gymnosperms{{Cite journal | last1 = Carnachan | first1 = S. M. | last2 = Harris | first2 = P. J. | doi = 10.1016/S0305-1978(00)00009-0 | title = Ferulic acid is bound to the primary cell walls of all gymnosperm families | journal = Biochemical Systematics and Ecology | volume = 28 | issue = 9 | pages = 865–879 | year = 2000 | pmid = 10913848| bibcode = 2000BioSE..28..865C }} (conifers, cycads, Ginkgo and Gnetales). {{citation needed|date=March 2013}}

In ferns, compounds such as kaempferol and its glucoside can be isolated from the methanolic extract of fronds of Phegopteris connectilis{{Cite journal | last1 = Adam | first1 = K. P. | title = Phenolic constituents of the fern Phegopteris connectilis | doi = 10.1016/S0031-9422(99)00326-X | journal = Phytochemistry | volume = 52 | issue = 5 | pages = 929–934 | year = 1999 | bibcode = 1999PChem..52..929A }} or kaempferol-3-O-rutinoside, a known bitter-tasting flavonoid glycoside, can be isolated from the rhizomes of Selliguea feei.Flavonoids and a proanthrocyanidin from rhizomes of Selliguea feei. Baek Nam-In, Kennelly E. J., Kardono L. B. S., Tsauri S., Padmawinata K., Soejarto D. D. and Kinghorn A. D., Phytochemistry, 1994, vol. 36, no. 2, pp. 513–518, {{INIST|3300075}} Hypogallic acid, caffeic acid, paeoniflorin and pikuroside can be isolated from the freshwater fern Salvinia molesta.{{Cite journal

| last1 = Choudhary | first1 = M. I.

| last2 = Naheed | first2 = N.

| last3 = Abbaskhan | first3 = A.

| last4 = Musharraf | first4 = S. G.

| last5 = Siddiqui | first5 = H.

| last6 = Atta-Ur-Rahman

| doi = 10.1016/j.phytochem.2007.10.028

| title = Phenolic and other constituents of fresh water fern Salvinia molesta

| journal = Phytochemistry

| volume = 69

| issue = 4

| pages = 1018–1023

| year = 2008

| pmid = 18177906

| bibcode = 2008PChem..69.1018C

}}

In conifers (Pinophyta), phenolics are stored in polyphenolic parenchyma cells, a tissue abundant in the phloem of all conifers.{{Cite book | last1 = Krokene | first1 = P. | last2 = Nagy | first2 = N. E. | last3 = Krekling | first3 = T. | doi = 10.1007/978-1-4020-8182-8_7 | chapter = Traumatic Resin Ducts and Polyphenolic Parenchyma Cells in Conifers | title = Induced Plant Resistance to Herbivory | pages = 147 | year = 2008 | isbn = 978-1-4020-8181-1 }}

The aquatic plant Myriophyllum spicatum produces ellagic, gallic and pyrogallic acids and (+)-catechin.{{Cite journal | last1 = Nakai | first1 = S. | title = Myriophyllum spicatum-released allelopathic polyphenols inhibiting growth of blue-green algae Microcystis aeruginosa | doi = 10.1016/S0043-1354(00)00039-7 | journal = Water Research | volume = 34 | issue = 11 | pages = 3026–3032 | year = 2000 | bibcode = 2000WatRe..34.3026N }}

Alkylresorcinols can be found in cereals.{{citation needed|date=March 2013}}

2,4-Bis(4-hydroxybenzyl)phenol is a phenolic compound found in the orchids Gastrodia elata and Galeola faberi.{{citation needed|date=March 2013}}

Phenolics can also be found in non-vascular land plants (bryophytes). Dihydrostilbenoids and bis(dibenzyls) can be found in liverworts (Marchantiophyta), for instance, the macrocycles cavicularin and riccardin C. Though lignin is absent in mosses (Bryophyta) and hornworts (Anthocerotophyta), some phenolics can be found in those two taxa.{{Cite journal | last1 = Erickson | first1 = M. | last2 = Miksche | first2 = G. E. | doi = 10.1016/0031-9422(74)85042-9 | title = On the occurrence of lignin or polyphenols in some mosses and liverworts | journal = Phytochemistry | volume = 13 | issue = 10 | pages = 2295–2299 | year = 1974 | bibcode = 1974PChem..13.2295E }} For instance, rosmarinic acid and a rosmarinic acid 3'-O-β-D-glucoside can be found in the hornwort Anthoceros agrestis.{{Cite journal | last1 = Vogelsang | first1 = K. | last2 = Schneider | first2 = B. | last3 = Petersen | first3 = M. | doi = 10.1007/s00425-005-0089-8 | title = Production of rosmarinic acid and a new rosmarinic acid 3′-O-β-D-glucoside in suspension cultures of the hornwort Anthoceros agrestis Paton | journal = Planta | volume = 223 | issue = 2 | pages = 369–373 | year = 2005 | pmid = 16133208| s2cid = 29302603 }}

The hardening of the protein component of insect cuticle has been shown to be due to the tanning action of an agent produced by oxidation of a phenolic substance forming sclerotin.{{citation needed|date=March 2013}} In the analogous hardening of the cockroach ootheca, the phenolic substance concerned is 3:4-dihydroxybenzoic acid (protocatechuic acid).{{Cite journal

| last1 = Hackman | first1 = R. H.

| last2 = Pryor | first2 = M. G.

| last3 = Todd | first3 = A. R.

| title = The occurrence of phenolic substances in arthropods

| journal = The Biochemical Journal

| volume = 43

| issue = 3

| pages = 474–477

| year = 1948

| pmid = 16748434

| pmc = 1274717

| doi=10.1042/bj0430474

}}

Acetosyringone is produced by the male leaffooted bug (Leptoglossus phyllopus) and used in its communication system.[http://www.pherobase.com/database/compound/compounds-detail-acetosyringone.php Acetosyringone on www.pherobase.com, the pheromones data base]{{Cite journal | last1 = Aldrich | first1 = J. R. | last2 = Blum | first2 = M. S. | last3 = Duffey | first3 = S. S. | last4 = Fales | first4 = H. M. | title = Male specific natural products in the bug, Leptoglossus phyllopus: Chemistry and possible function | doi = 10.1016/0022-1910(76)90094-9 | journal = Journal of Insect Physiology | volume = 22 | issue = 9 | pages = 1201–1206 | year = 1976 | bibcode = 1976JInsP..22.1201A }}{{Cite journal | last1 = Aldrich | first1 = J. R. | last2 = Blum | first2 = M. S. | last3 = Fales | first3 = H. M. | title = Species-specific natural products of adult male leaf-footed bugs (Hemiptera: Heteroptera) | doi = 10.1007/BF00987687 | journal = Journal of Chemical Ecology | volume = 5 | pages = 53–62 | year = 1979 | issue = 1 | bibcode = 1979JCEco...5...53A | s2cid = 34346907 }} Guaiacol is produced in the gut of Desert locusts, Schistocerca gregaria, by the breakdown of plant material. This process is undertaken by the gut bacterium Pantoea agglomerans.{{Cite journal|last1=Dillon|first1=R.J.|last2=Vennard|first2=C.T.|last3=Charnley|first3=A.K.|date=April 2002|title=A Note: Gut bacteria produce components of a locust cohesion pheromone|journal=Journal of Applied Microbiology|language=en|volume=92|issue=4|pages=759–763|doi=10.1046/j.1365-2672.2002.01581.x|pmid=11966918|s2cid=8561972|issn=1364-5072|doi-access=free}} Guaiacol is one of the main components of the pheromones that cause locust swarming.{{Cite journal | doi=10.1038/35002669| pmid=10706273| title=Exploitation of gut bacteria in the locust| journal=Nature| volume=403| issue=6772| pages=851| year=2000| last1=Dillon| first1=Rod J.| last2=Vennard| first2=Chris T.| last3=Charnley| first3=A. Keith| s2cid=5207502| doi-access=free}} Orcinol has been detected in the "toxic glue" of the ant species Camponotus saundersi.{{citation needed|date=March 2013}} Rhynchophorus ferrugineus (red palm weevil) use 2-methoxy-4-vinylphenol for chemical signaling (pheromones).[http://www.pherobase.com/database/compound/compounds-detail-2-methoxy-4-vinylphenol.php Semiochemical - 2-methoxy-4-vinylphenol], Pherobase.com Other simple and complex phenols can be found in eusocial ants (such as Crematogaster) as components of venom.{{cite journal | last1 = Marlier | first1 = J. | last2 = Quinet | first2 = Y. | last3 = Debiseau | first3 = J. | year = 2004 | title = Defensive Behaviour and Biological Activities of the Abdominal Secretion in the Ant Crematogaster Scutellaris (Hymenoptera: Myrmicinae) | url = https://dipot.ulb.ac.be/dspace/bitstream/2013/18833/1/Elsevier_6161.pdf| journal = Behavioural Processes | volume = 67 | issue = 3| pages = 427–40 | doi=10.1016/j.beproc.2004.07.003| pmid = 15518992 | s2cid = 21599793 }}

In female elephants, the two compounds 3-ethyl phenol and 2-ethyl 4,5 dimethylphenol have been detected in urine samples.Urinary, temporal gland, and breath odors from Asian elephants of Mudumalai National Park. L. E. L. Rasmussen and V. Krishnamurthy, Gajah, the Journal of the Asian Elephant Specialist Group, January 2001, Number 20, pages 1-8 ([http://www.asesg.org/PDFfiles/Gajah%20scanned%20BW/Gajah%2020%20%20January%202001.pdf#page=3 article]) Temporal glands secretion examination showed the presence of phenol, m-cresol and p-cresol (4-methyl phenol) during musth in male elephants.{{Cite journal | last1 = Rasmussen | first1 = L. E. L. | last2 = Perrin | first2 = T. E. | doi = 10.1016/S0031-9384(99)00114-6 | title = Physiological Correlates of Musth | journal = Physiology & Behavior | volume = 67 | issue = 4 | pages = 539–49 | year = 1999 | pmid = 10549891| s2cid = 21368454 }}"Musth in elephants". Deepa Ananth, Zoo's print journal, 15(5), pp. 259-262 ([http://www.zoosprint.org/ZooPrintJournal/2000/May/259-262.pdf article] {{Webarchive|url=https://web.archive.org/web/20180604223031/http://www.zoosprint.org/ZooPrintJournal/2000/May/259-262.pdf |date=2018-06-04 }}){{Cite journal | last1 = Adams | first1 = J. | last2 = Garcia | first2 = A. | last3 = Foote | first3 = C. S. | title = Some chemical constituents of the secretion from the temporal gland of the African elephant (Loxodonta africana) | doi = 10.1007/BF00988256 | journal = Journal of Chemical Ecology | volume = 4 | pages = 17–25 | year = 1978 | issue = 1 | bibcode = 1978JCEco...4...17A | s2cid = 45857570 }}

p-Cresol and o-cresol are also components of the human sweat.{{citation needed|date=March 2013}} P-cresol is also a major component in pig odor.{{Cite web | url=http://www.sciam.com/article.cfm?id=why-study-pig-odor | title=Why study pig odor?}}

4-Ethylphenol, 1,2-dihydroxybenzene, 3-hydroxyacetophenone, 4-methyl-1,2-dihydroxybenzene, 4-methoxyacetophenone, 5-methoxysalicylic acid, salicylaldehyde, and 3-hydroxybenzoic acid are components of castoreum, the exudate from the castor sacs of the mature North American beaver (Castor canadensis) and the European beaver (Castor fiber), used in perfumery.{{Cite journal | last1 = Müller-Schwarze | first1 = D. | last2 = Houlihan | first2 = P. W. | doi = 10.1007/BF00994195 | title = Pheromonal activity of single castoreum constituents in beaver, Castor canadensis | journal = Journal of Chemical Ecology | volume = 17 | issue = 4 | pages = 715–34 | year = 1991 | pmid = 24258917| bibcode = 1991JCEco..17..715M | s2cid = 29937875 }}

In some cases of natural phenols, they are present in vegetative foliage to discourage herbivory, such as in the case of Western poison oak.C.Michael Hogan (2008) Western poison-oak: Toxicodendron diversilobum, GlobalTwitcher, ed. Nicklas Stromberg {{cite web |url=http://globaltwitcher.auderis.se/artspec_information.asp?thingid=82914 |title=Archived copy |access-date=2009-07-21 |url-status=dead |archive-url=https://web.archive.org/web/20090721044257/http://globaltwitcher.auderis.se/artspec_information.asp?thingid=82914 |archive-date=2009-07-21 }}

In soils, it is assumed that larger amounts of phenols are released from decomposing plant litter rather than from throughfall in any natural plant community.{{citation needed|date=March 2013}} Decomposition of dead plant material causes complex organic compounds to be slowly oxidized lignin-like humus or to break down into simpler forms (sugars and amino sugars, aliphatic and phenolic organic acids), which are further transformed into microbial biomass (microbial humus) or are reorganized, and further oxidized, into humic assemblages (fulvic and humic acids), which bind to clay minerals and metal hydroxides.{{citation needed|date=March 2013}} There has been a long debate about the ability of plants to uptake humic substances from their root systems and to metabolize them.{{citation needed|date=March 2013}} There is now a consensus about how humus plays a hormonal role rather than simply a nutritional role in plant physiology.{{citation needed|date=March 2013}}

In the soil, soluble phenols face four different fates. They might be degraded and mineralized as a carbon source by heterotrophic microorganisms; they can be transformed into insoluble and recalcitrant humic substances by polymerization and condensation reactions (with the contribution of soil organisms); they might adsorb to clay minerals or form chelates with aluminium or iron ions; or they might remain in dissolved form, leached by percolating water, and finally leave the ecosystem as part of dissolved organic carbon (DOC).

Leaching is the process by which cations such as iron (Fe) and aluminum (Al), as well as organic matter, are removed from the litterfall and transported downward into the soil below. This process is known as podzolization and is particularly intense in boreal and cool temperate forests that are mainly constituted by coniferous pines, whose litterfall is rich in phenolic compounds and fulvic acid.Biogeochemistry: An Analysis of Global Change. 2nd Edition. William H. Schlesinger, Academic Press, 1997, 108, 135, 152–158, 180–183, 191–194

Phenolic compounds can act as protective agents, inhibitors, natural animal toxicants and pesticides against invading organisms, i.e. herbivores, nematodes, phytophagous insects, and fungal and bacterial pathogens. The scent and pigmentation conferred by other phenolics can attract symbiotic microbes, pollinators and animals that disperse fruits.{{cite journal | last1 = Bhattacharya | first1 = A| year = 2010 | title = Review: The roles of plant phenolics in defence and communication during Agrobacterium and Rhizobium infection | journal = Mol Plant Pathol | volume = 11 | issue = 5| pages = 705–19 | pmid = 20696007 | doi=10.1111/j.1364-3703.2010.00625.x|display-authors=etal| pmc = 6640454 }}

Volatile phenolic compounds are found in plant resin where they may attract benefactors such as parasitoids or predators of the herbivores that attack the plant.Plant Resins: Chemistry, evolution, ecology, and ethnobotany, by Jean Langenheim, Timber Press, Portland, Oregon. 2003

In the kelp species Alaria marginata, phenolics act as chemical defence against herbivores.{{Cite journal | last1 = Steinberg | first1 = P. D. | title = Algal Chemical Defense Against Herbivores: Allocation of Phenolic Compounds in the Kelp Alaria marginata | doi = 10.1126/science.223.4634.405 | journal = Science | volume = 223 | issue = 4634 | pages = 405–407 | year = 1984 | pmid = 17829890| bibcode = 1984Sci...223..405S | s2cid = 36409146 }} In tropical Sargassum and Turbinaria species that are often preferentially consumed by herbivorous fishes and echinoids, there is a relatively low level of phenolics and tannins.{{Cite journal | last1 = Steinberg | first1 = P. D. | title = Chemical defenses and the susceptibility of tropical marine brown algae to herbivores | doi = 10.1007/BF00410374 | journal = Oecologia | volume = 69 | issue = 4 | pages = 628–630 | year = 1986 | pmid = 28311627| bibcode = 1986Oecol..69..628S | s2cid = 19551247 }} Marine allelochemicals generally are present in greater quantity and diversity in tropical than in temperate regions. Marine algal phenolics have been reported as an apparent exception to this biogeographic trend. High phenolic concentrations occur in brown algae species (orders Dictyotales and Fucales) from both temperate and tropical regions, indicating that latitude alone is not a reasonable predictor of plant phenolic concentrations.{{cite journal|jstor=4219911|doi=10.1007/BF00317150|pmid=28311874|title=Biogeographic Comparisons of Marine Algal Polyphenolics: Evidence against a Latitudinal Trend|first1=Nancy M. |last1=Targett|first2= Loren D.|last2=Coen|first3= Anne A. |last3=Boettcher |first4= Christopher E. |last4=Tanner|volume=89|issue= 4 |year=1992|pages= 464–470 |journal=Oecologia|bibcode=1992Oecol..89..464T|s2cid=5655010}}

In Vitis vinifera grape, trans-resveratrol is a phytoalexin produced against the growth of fungal pathogens such as Botrytis cinerea{{cite journal|url=http://www.sipav.org/main/jpp/volumes/0309/030909.pdf |title=The role of grape polyphenols on trans-resveratrol activity against Botrytis cinerea and of fungal laccase on the solubility of putative grape PR proteins |author=F. Favaron, M. Lucchetta, S. Odorizzi, A. T. Pais da Cunha and L. Sella |journal=Journal of Plant Pathology |year=2009 |volume=91 |issue=3 |pages=579–588 |access-date=2011-01-22 | doi=10.4454/jpp.v91i3.549|doi-broken-date=1 November 2024 }} and delta-viniferin is another grapevine phytoalexin produced following fungal infection by Plasmopara viticola.{{Cite journal

| last1 = Timperio | first1 = A. M.

| last2 = d’Alessandro | first2 = A.

| last3 = Fagioni | first3 = M.

| last4 = Magro | first4 = P.

| last5 = Zolla | first5 = L.

| title = Production of the phytoalexins trans-resveratrol and delta-viniferin in two economy-relevant grape cultivars upon infection with Botrytis cinerea in field conditions

| doi = 10.1016/j.plaphy.2011.07.008

| journal = Plant Physiology and Biochemistry

| volume = 50

| issue = 1

| pages = 65–71

| year = 2012

| pmid = 21821423

| bibcode = 2012PlPB...50...65T

}} Pinosylvin is a pre-infectious stilbenoid toxin (i.e. synthesized prior to infection), contrary to phytoalexins, which are synthesized during infection. It is present in the heartwood of Pinaceae.{{Cite journal | last1 = Hovelstad | first1 = H. | last2 = Leirset | first2 = I. | last3 = Oyaas | first3 = K. | last4 = Fiksdahl | first4 = A. | title = Screening Analyses of Pinosylvin Stilbenes, Resin Acids and Lignans in Norwegian Conifers | doi = 10.3390/11010103 | journal = Molecules | volume = 11 | issue = 1 | pages = 103–114 | year = 2006 | pmid = 17962750| pmc = 6148674| doi-access = free }} It is a fungitoxin protecting the wood from fungal infection.{{Cite journal | last1 = Lee | first1 = S. K. | last2 = Lee | first2 = H. J. | last3 = Min | first3 = H. Y. | last4 = Park | first4 = E. J. | last5 = Lee | first5 = K. M. | last6 = Ahn | first6 = Y. H. | last7 = Cho | first7 = Y. J. | last8 = Pyee | first8 = J. H. | doi = 10.1016/j.fitote.2004.12.004 | title = Antibacterial and antifungal activity of pinosylvin, a constituent of pine | journal = Fitoterapia | volume = 76 | issue = 2 | pages = 258–260 | year = 2005 | pmid = 15752644}}

Sakuranetin is a flavanone, a type of flavonoid. It can be found in Polymnia fruticosa{{Cite web |url=http://home.ncifcrf.gov/mtdp/Catalog/compounds/407228.html |title=Sakuranetin |website=home.ncifcrf.gov |access-date=2018-12-02 |archive-url=https://web.archive.org/web/20181203010928/https://home.ncifcrf.gov/mtdp/Catalog/compounds/407228.html |archive-date=2018-12-03 |url-status=dead }} and rice, where it acts as a phytoalexin against spore germination of Pyricularia oryzae.Sakuranetin, a flavonone phytoalexin from ultraviolet-irradiated rice leaves, Kodama O., Miyakawa J., Akatsuka T. and Kiyosawa S., Phytochemistry, 1992, volume 31, number 11, pp. 3807–3809, {{INIST|4682303}} In Sorghum, the SbF3'H2 gene, encoding a flavonoid 3'-hydroxylase, seems to be expressed in pathogen-specific 3-deoxyanthocyanidin phytoalexins synthesis,{{Cite journal | last1 = Shih | first1 = C. -H. | last2 = Chu | first2 = I. K. | last3 = Yip | first3 = W. K. | last4 = Lo | first4 = C. | title = Differential Expression of Two Flavonoid 3'-Hydroxylase cDNAs Involved in Biosynthesis of Anthocyanin Pigments and 3-Deoxyanthocyanidin Phytoalexins in Sorghum | doi = 10.1093/pcp/pcl003 | journal = Plant and Cell Physiology | volume = 47 | issue = 10 | pages = 1412–1419 | year = 2006 | pmid = 16943219| doi-access = free }} for example in Sorghum-Colletotrichum interactions."Biosynthesis and regulation of 3-deoxyanthocyanidin phytoalexins induced during Sorghum-Colletotrichum interaction: Heterologous expression in maize". Chopra Surinder, Gaffoor Iffa, Ibraheem Farag, Poster at the American Society of Plant Biologists ([http://abstracts.aspb.org/pb2009/public/P48/P48067.html abstract] {{webarchive|url=https://web.archive.org/web/20110725021532/http://abstracts.aspb.org/pb2009/public/P48/P48067.html |date=2011-07-25 }})

6-Methoxymellein is a dihydroisocoumarin and a phytoalexin induced in carrot slices by UV-C,{{Cite journal | last1 = Mercier | first1 = J. | last2 = Arul | first2 = J. | last3 = Ponnampalam | first3 = R. | last4 = Boulet | first4 = M. | title = Induction of 6-Methoxymellein and Resistance to Storage Pathogens in Carrot Slices by UV-C | doi = 10.1111/j.1439-0434.1993.tb01324.x | journal = Journal of Phytopathology | volume = 137 | pages = 44–54 | year = 1993 }} that allows resistance to Botrytis cinerea{{Cite journal | last1 = Hoffman | first1 = R. | last2 = Heale | first2 = J. B. | doi = 10.1016/0885-5765(87)90083-X | title = Cell death, 6-methoxymellein accumulation, and induced resistance to Botrytis cinerea in carrot root slices | journal = Physiological and Molecular Plant Pathology | volume = 30 | pages = 67–75 | year = 1987 | issue = 1 | bibcode = 1987PMPP...30...67H }} and other microorganisms.{{Cite journal | last1 = Kurosaki | first1 = F. | last2 = Nishi | first2 = A. | doi = 10.1016/S0031-9422(00)86959-9 | title = Isolation and antimicrobial activity of the phytoalexin 6-methoxymellein from cultured carrot cells | journal = Phytochemistry | volume = 22 | issue = 3 | pages = 669–672 | year = 1983 | bibcode = 1983PChem..22..669K }}

Danielone is a phytoalexin found in the papaya fruit. This compound showed high antifungal activity against Colletotrichum gloesporioides, a pathogenic fungus of papaya.Danielone, a phytoalexin from papaya fruit. Echeverri F., Torres F., Quinones W., Cardona G., Archbold R., Roldan J., Brito I., Luis J. G., and Lahlou U. E.-H., Phytochemistry, 1997, vol. 44, no. 2, pp. 255–256, {{INIST|2558881}}

Stilbenes are produced in Eucalyptus sideroxylon in case of pathogens attacks. Such compounds can be implied in the hypersensitive response of plants. High levels of phenolics in some woods can explain their natural preservation against rot.{{cite journal |title=Inhibition of wood-rotting fungi by stilbenes and other polyphenols in Eucalyptus sideroxylon |first1=John H. |last1=Hart |first2=W. E. |last2=Hillis |journal=Phytopathology |volume=64 |pages=939–48 |year=1974 |doi=10.1094/Phyto-64-939 |issue=7}}

In plants, VirA is a protein histidine kinase which senses certain sugars and phenolic compounds. These compounds are typically found from wounded plants, and as a result VirA is used by Agrobacterium tumefaciens to locate potential host organisms for infection.{{cite journal|last1=Brencic|first1=Anja|last2=Winans|first2=Stephen C.|title=Detection of and Response to Signals Involved in Host-Microbe Interactions by Plant-Associated Bacteria|journal=Microbiol Mol Biol Rev|date=March 2005|volume=69|issue=1|pages=155–194|pmc=1082791|pmid=15755957|doi=10.1128/mmbr.69.1.155-194.2005}}

Natural phenols can be involved in allelopathic interactions, for example in soil{{cite journal |last1=Blum |first1=Udo |last2=Shafer |first2=Steven R. |last3=Lehman |first3=Mary E. |title=Evidence for Inhibitory Allelopathic Interactions Involving Phenolic Acids in Field Soils: Concepts vs. an Experimental Model |journal=Critical Reviews in Plant Sciences |volume=18 |pages=673–93 |year=1999 |doi=10.1080/07352689991309441 |issue=5|bibcode=1999CRvPS..18..673B }} or in water. Juglone is an example of such a molecule inhibiting the growth of other plant species around walnut trees.{{citation needed|date=March 2013}} The aquatic vascular plant Myriophyllum spicatum produces ellagic, gallic and pyrogallic acids and (+)-catechin, allelopathic phenolic compounds inhibiting the growth of blue-green alga Microcystis aeruginosa.

Phenolics, and in particular flavonoids and isoflavonoids, may be involved in endomycorrhizae formation.{{Cite journal | last1 = Morandi | first1 = D. | title = Occurrence of phytoalexins and phenolic compounds in endomycorrhizal interactions, and their potential role in biological control | doi = 10.1007/BF02257529 | journal = Plant and Soil | volume = 185 | issue = 2 | pages = 241–305 | year = 1996 | bibcode = 1996PlSoi.185..241M | s2cid = 30091640 }}

Acetosyringone has been best known for its involvement in plant-pathogen recognition,"Involvement of acetosyringone in plant-pathogen recognition". Baker C. Jacyn, Mock Norton M., Whitaker Bruce D., Roberts Daniel P., Rice Clifford P., Deahl Kenneth L. and Aver'Yanov Andrey A., Biochemical and Biophysical Research Communications, 2005, volume 328, number 1, pp. 130–136, {{INIST|16656426}} especially its role as a signal attracting and transforming unique, oncogenic bacteria in genus Agrobacterium.{{citation needed|date=March 2013}} The virA gene on the Ti plasmid in the genome of Agrobacterium tumefaciens and Agrobacterium rhizogenes is used by these soil bacteria to infect plants, via its encoding for a receptor for acetosyringone and other phenolic phytochemicals exuded by plant wounds.{{Cite journal | last1 = Schrammeijer | first1 = B. | last2 = Beijersbergen | first2 = A. | last3 = Idler | first3 = K. B. | last4 = Melchers | first4 = L. S. | last5 = Thompson | first5 = D. V. | last6 = Hooykaas | first6 = P. J. | title = Sequence analysis of the vir-region from Agrobacterium tumefaciens octopine Ti plasmid pTi15955 | doi = 10.1093/jexbot/51.347.1167 | journal = Journal of Experimental Botany | volume = 51 | issue = 347 | pages = 1167–1169 | year = 2000 | pmid = 10948245| doi-access = free }} This compound also allows higher transformation efficiency in plants, in A. tumefaciens mediated transformation procedures, and so is of importance in plant biotechnology.{{Cite journal | last1 = Sheikholeslam | first1 = S. N. | last2 = Weeks | first2 = D. P. | doi = 10.1007/BF00021308 | title = Acetosyringone promotes high efficiency transformation of Arabidopsis thaliana explants by Agrobacterium tumefaciens | journal = Plant Molecular Biology | volume = 8 | issue = 4 | pages = 291–298 | year = 1987 | pmid = 24301191| s2cid = 32005770 }}

{{Main|Phenolic content in wine|Phenolic content in tea}}

{{See also|List of phytochemicals in food}}

Notable sources of natural phenols in human nutrition include berries, tea, beer, olive oil, chocolate or cocoa, coffee, pomegranates, popcorn, yerba maté, fruits and fruit based drinks (including cider, wine and vinegar) and vegetables. Herbs and spices, nuts (walnuts, peanut) and algae are also potentially significant for supplying certain natural phenols.

Natural phenols can also be found in fatty matrices like olive oil.{{cite journal |last1=Gutfinger |first1=T. |title=Polyphenols in olive oils |journal=Journal of the American Oil Chemists' Society |volume=58 |pages=966–8 |year=1981 |doi=10.1007/BF02659771 |issue=11|s2cid=85367601 }} Unfiltered olive oil has the higher levels of phenols, or polar phenols that form a complex phenol-protein complex.

Phenolic compounds, when used in beverages, such as prune juice, have been shown to be helpful in the color and sensory components, such as alleviating bitterness.{{cite journal | doi = 10.1021/jf970831x | title = Phenolic Composition and Antioxidant Activity of Prunes and Prune Juice (Prunus domestica) | year = 1998 | last1 = Donovan | first1 = Jennifer L. | last2 = Meyer | first2 = Anne S. | last3 = Waterhouse | first3 = Andrew L. | journal = Journal of Agricultural and Food Chemistry | volume = 46 | issue = 4 | pages = 1247–1252 | bibcode = 1998JAFC...46.1247D }}

Some advocates for organic farming claim that organically grown potatoes, oranges, and leaf vegetables have more phenolic compounds and these may provide antioxidant protection against heart disease and cancer.Asami, Danny K. [http://pubs.acs.org/cgi-bin/sample.cgi/jafcau/2003/51/i05/html/jf020635c.html "Comparison of the Total Phenolic and Ascorbic Acid Content of Freeze-Dried and Air-Dried Marionberry, Strawberry, and Corn Grown Using Conventional, Organic, and Sustainable Agricultural Practices"]. Journal of Agricultural and Food Chemistry (American Chemical Society), 51 (5), 1237–1241, 2003. 10.1021/jf020635c S0021-8561(02)00635-0. Retrieved 10-Apr-2006. However, evidence on substantial differences between organic food and conventional food is insufficient to support claims that organic food is safer or healthier than conventional food.{{cite journal |last=Smith-Spangler|first=C. |author2=Brandeau, M. L.|author2-link= Margaret Brandeau |author3=Hunter, G. E. |author4=Bavinger, J. C. |author5=Pearson, M. |author6=Eschbach, P. J. |author7=Sundaram, V. |author8=Liu, H. |author9=Schirmer, P. |author10=Stave, C. |author11=Olkin, I. |author12=Bravata, D. M. |title=Are organic foods safer or healthier than conventional alternatives?: a systematic review |journal=Annals of Internal Medicine |date=September 4, 2012 |volume=157 |issue=5 |pages=348–366 |pmid=22944875 |doi=10.7326/0003-4819-157-5-201209040-00007|s2cid=21463708 }}Blair, Robert. (2012). Organic Production and Food Quality: A Down to Earth Analysis. Wiley-Blackwell, Oxford, UK. {{ISBN|978-0-8138-1217-5}}

In animals and humans, after ingestion, natural phenols become part of the xenobiotic metabolism. In subsequent phase II reactions, these activated metabolites are conjugated with charged species such as glutathione, sulfate, glycine or glucuronic acid. These reactions are catalysed by a large group of broad-specificity transferases. UGT1A6 is a human gene encoding a phenol UDP glucuronosyltransferase active on simple phenols."Cloning and substrate specificity of a human phenol UDP glucuronosyltransferase expressed in COS-7 cells". David Harding, Sylvie Fournel-Gigleux, Michael R. Jackson and Brian Burchell, Proc. Natl. Acad. Sci. USA, November 1988, Volume 85, pp. 8381–8385, ([http://www.pnas.org/content/85/22/8381.short abstract]) The enzyme encoded by the gene UGT1A8 has glucuronidase activity with many substrates including coumarins, anthraquinones and flavones.{{cite journal |author1=Ritter J. K. |author2=Chen F. |author3=Sheen Y. Y. |author4=Tran H. M. |author5=Kimura S. |author6=Yeatman M. T. |author7=Owens I. S. | title = A novel complex locus UGT1 encodes human bilirubin, phenol, and other UDP-glucuronosyltransferase isozymes with identical carboxyl termini | journal = J Biol Chem | volume = 267 | issue = 5 | pages = 3257–61 |date=Mar 1992 |doi=10.1016/S0021-9258(19)50724-4 | pmid = 1339448 |doi-access=free }}

{{reflist|30em}}

• Biochemistry of phenolic compounds, by J. B. Harborne, 1964, Academic Press ([https://books.google.com/books?id=_-lqAAAAMAAJ Google Books])
• Plant phenolics, by Pascal Ribéreau-Gayon, 1972, Oliver and Boyd Editions ([https://books.google.com/books?id=EHzwAAAAMAAJ Google Books], {{ISBN|0050025120}}, {{ISBN|9780050025123}})
• The Biochemistry of plant phenolics, by C. F. van Sumere and P. J. Lea, Phytochemical Society of Europe, 1985, Clarendon Press ([https://books.google.com/books?id=YwmLAAAAIAAJ Google Books], {{ISBN|9780198541707}})
• Biochemistry of Phenolic Compounds, by Wilfred Vermerris and Ralph Nicholson, 2006, Springer ([https://books.google.com/books?id=uLzdv8fsRxYC&dq=Biochemistry+of+Phenolic+Compounds&pg=PA3 Google book])

• [http://www.britannica.com/EBchecked/topic/455507/phenol/278031/Natural-sources-of-phenols Natural sources of phenols on www.britannica.com]

• Phenol-Explorer ([http://www.phenol-explorer.eu phenol-explorer.eu]), a database dedicated to phenolics found in food by Augustin Scalbert, INRA Clermont-Ferrand, Unité de Nutrition Humaine (Human food unit)
• [http://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:33853 Phenols] at ChEBI (Chemical Entities of Biological Interest)
• [https://web.archive.org/web/20181002215232/https://www.ebi.ac.uk/chembldb/index.php ChEMBLdb], a database of bioactive drug-like small molecules by the European Bioinformatics Institute
• Foodb, a database of compounds found in food

{{Secondary metabolites}}

{{Phytochemical}}

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Category:Functional groups

Category:Disinfectants