{{Short description|Chemical compound found in some lichens}} {{Chembox <!-- Images --> | ImageFile = Parietinic acid.svg | ImageSize = 200px <!-- Names --> | IUPACName = 4,5-Dihydroxy-7-methoxy-9,10-dioxo-9,10-dihydro-2-anthracenecarboxylic acid | OtherNames = {{ubl |1,8-Dihydroxy-3-methoxy-6-carboxy-9,10-anthraquinone |1,8-Dihydroxy-6-methoxy-9,10-dioxo-9,10-dihydroanthracene-3-carboxylic acid }} <!-- Sections --> | Section1 = {{Chembox Identifiers | CASNo = 17636-18-9 | ChEBI = 144288 | ChEMBL = | ChemSpiderID = 9682704 | DrugBank = | EC_number = | PubChem = | InChI = InChI=1S/C16H10O7/c1-23-7-4-9-13(11(18)5-7)15(20)12-8(14(9)19)2-6(16(21)22)3-10(12)17/h2-5,17-18H,1H3,(H,21,22) | InChIKey = HEULMVKOOVHXME-UHFFFAOYSA-N | SMILES = COC1=CC2=C(C(=C1)O)C(=O)C3=C(C2=O)C=C(C=C3O)C(=O)O }} | Section2 = {{Chembox Properties | C=16|H=10|O=7 | Appearance = orange needles | Density = | MeltingPtC = 304–305 | MeltingPt_notes = | BoilingPt = | Solubility = }} | Section3 = {{Chembox Hazards | MainHazards = | FlashPt = | AutoignitionPt = }} }}

'''Parietinic acid''' is an organic compound in the structural class of chemicals known as anthraquinones. It is found in many species of the lichen family Teloschistaceae. The substance was first reported in the literature by the German chemist Walter Eschrich in 1958.<ref name="Eschrich 1958"/>

==Occurrence==

Originally isolated from the lichen ''Xanthoria parietina'', it has since been identified in many lichens of the family Teloschistaceae.<ref name="Huneck 1996"/> In 1970, Johan Santesson proposed a possible biogenetic relationship between the anthraqunone compounds commonly found in ''Caloplaca''. According to this scheme, emodin is methylated to give parietin, which then undergoes three successive oxidations, sequentially forming fallacinol, fallacinal, and then parietinic acid.<ref name="Santesson 1970"/> A {{lichengloss|chemosyndrome}} is a set of biosynthetically related compounds produced by a lichen. In 2002, Ulrik Søchting and Patrik Frödén identified chemosyndrome&nbsp;A, the most common chemosyndrome in the genus ''Teloschistes'' and in the entire family Teloschistaceae, which features parietin as the main substance and smaller proportions of teloschistin, fallacinal, parietinic acid, and emodin.<ref name="Søchting & Frödén 2002"/>

==Properties== In its purified form, parietinic acid exists as orange needles with a melting point of {{convert|304|–|305|C|F}}. Its ultraviolet spectrum has two peaks of maximum absorption (λ<sub>max</sub>) at 325 and 435&nbsp;nm, and its infrared spectrum has two peaks at 1629 and 1700&nbsp;cm<sup>−1</sup>.<ref name="Huneck 1996"/>

Parietinic acid was shown to have antifungal activity and antibacterial activity in laboratory tests.<ref name="Manojlovic et al. 2002"/><ref name="Łaska et al. 2016"/>

==References== {{Reflist|refs=

<ref name="Eschrich 1958">{{cite journal |last=Eschrich |first=Walter |year=1958 |title=Parietic acid, a new component of the yellow wall lichen ''Xanthoria parietina'' (L.) Th. Fr |journal=Biochemische Zeitschrift |volume=330 |issue=1 |pages=73–78 |pmid=13535618 |language=de}}</ref>

<ref name="Manojlovic et al. 2002">{{cite journal |last1=Manojlovic |first1=Nedeljko T. |last2=Solujic |first2=Slavica |last3=Sukdolak |first3=Slobodan |title=Antimicrobial activity of an extract and anthraquinones from ''Caloplaca schaereri'' |journal=The Lichenologist |volume=34 |issue=1 |year=2002 |doi=10.1006/lich.2001.0365 |pages=83–85}}</ref>

<ref name="Huneck 1996">{{cite book |last=Huneck |first=Siegfried |title=Identification of Lichen Substances |publisher=Springer Berlin Heidelberg |publication-place=Berlin, Heidelberg |year=1996 |isbn=978-3-642-85245-9 |oclc=851387266 |page=180}}</ref>

<ref name="Łaska et al. 2016">{{cite journal |last1=Łaska |first1=G. |last2=Kiercul |first2=S. |last3=Piotrowska-Niczyporuk |first3=A. |last4=Jacob |first4=M. |last5=Pasco |first5=D. |title=Secondary metabolites isolated from ''Xanthoria parietina'' (L.) Th. Fr. lichen and their biological activity |journal=Planta Medica |volume=81 |issue=S 01 |year=2016 |doi=10.1055/s-0036-1596402 |pages=S1–S381}}</ref>

<ref name="Santesson 1970">{{cite journal |last1=Santesson |first1=Johan |title=Anthraquinones in ''Caloplaca'' |journal=Phytochemistry |volume=9 |issue=10 |year=1970 |doi=10.1016/S0031-9422(00)85380-7 |pages=2149–2166}}</ref>

<ref name="Søchting & Frödén 2002">{{cite journal |last1=Søchting |first1=Ulrik |last2=Frödén |first2=Patrik |year=2002 |title=Chemosyndromes in the lichen genus ''Teloschistes'' (Teloschistaceae, Lecanorales) |journal=Mycological Progress |volume=1 |issue=3 |pages=257–266}}</ref>

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Category:Anthraquinones Category:Lichen products