{{Short description|Chemical compound found in some lichens}} {{Chembox <!-- Images --> | ImageFile = Salazinic acid.svg | ImageSize = <!-- Names --> | IUPACName = 1,3-Dihydro-1,4,10-trihydroxy-5-(hydroxymethyl)-8-methyl-3,7-dioxo-7''H''-isobenzofuro[4,5-''b''][1,4]benzodioxepin-11-carboxaldehyde | OtherNames = <!-- Sections --> | Section1 = {{Chembox Identifiers | CASNo = 521-39-1 | ChEBI = | ChEMBL = 172439 | ChemSpiderID =4478508 | DrugBank = | EC_number = 208-312-0 | PubChem = 5320418 | InChI = InChI=1S/C18H12O10/c1-5-2-8(21)6(3-19)13-9(5)16(23)27-14-7(4-20)12(22)10-11(15(14)26-13)18(25)28-17(10)24/h2-3,18,20-22,25H,4H2,1H3 | InChIKey = QQTKVXCQLZIJPP-UHFFFAOYSA-N | SMILES = CC1=CC(=C(C2=C1C(=O)OC3=C(O2)C4=C(C(=C3CO)O)C(=O)OC4O)C=O)O }} | Section2 = {{Chembox Properties | C=18|H=12|O=10 | Appearance = | Density = | MeltingPtC = | MeltingPt_notes = | BoilingPt = | Solubility = }} | Section3 = {{Chembox Hazards | MainHazards = | FlashPt = | AutoignitionPt = }} }}
'''Salazinic acid''' is a [[depsidone]] with a [[lactone]] ring. It is found in some [[lichen]]s, and is especially prevalent in ''[[Parmotrema]]'' and ''[[Bulbothrix]]'', where its presence or absence is often used to help [[classification (biology)|classify]] species in those [[genus|genera]].
==History==
In 1897, [[Friedrich Wilhelm Zopf]] named the chemical he originally isolated from the African species ''[[Stereocaulon salazinum]]'' as salazinic acid.<ref name="Zopf 1897"/> Later studies showed that the compound he named was actually [[norstictic acid]].<ref name="Asahina & Shibata 1954"/>
In 1933, [[Yasuhiko Asahina]] and J. Asano studied salazinic acid they had isolated from ''[[Parmelia cetrata]]'', and found a unique [[ring (chemistry)|ring system]] with seven members containing two [[phenols|phenolic]] components. The fundamental structure was named [[depsidone]], that is, a seven-membered ring with an oxygen bridge binding two [[aromaticity|aromatic]] rings.<ref name="Shibata 2000"/> Japanese chemists demonstrated in the late 1960s that the isolated [[mycobiont]] of the lichen ''[[Ramalina crassa]]'' could produce salazinic acid when grown in [[microbiological culture|laboratory culture]].<ref name="Komiya & Shibata 1969"/> Subsequent studies tried to determine the influence of environmental factors on the production of salazinic acid in culture. For example, two studies in the late 1980s showed that only 4-''O''-demethylbarbatic acid (a precursor of salazinic acid) was produced by the isolated mycobiont of ''[[Ramalina siliquosa]]'' when grown in malt [[yeast extract]] medium supplemented with low amounts of [[sucrose]].<ref name="Hamada & Ueno 1987"/><ref name="Hamada 1989"/> When extra sucrose was added to the growth medium, the production of salazinic acid was observed; the increased [[Osmotic concentration|osmolality]] enhances the reaction from 4-''O''-demethylbarbatic acid to salazinic acid.<ref name="Hamada & Miyagawa 1995"/>
==Properties== Salazinic acid has a [[molecular formula]] of C<sub>18</sub>H<sub>12</sub>O<sub>10</sub>, and a [[molecular mass]] of 388.3 grams/[[mole (unit)|mole]]. In its purified form, it exists as colourless needles with a [[melting point]] range between {{convert|260|–|268|C|F}} that undergo a colour change to brown at about {{convert|240|C|F}}. Its [[solubility]] in water is about 27 milligrams per litre.<ref name="Iskandar & Syers 1971"/>
The compound has been shown in ''[[in vitro]]'' studies to have [[antimicrobial]] properties,<ref name="Candan et al. 2007"/><ref name="Manojlovic et al. 2012"/> but it did not have any substantive [[antimycobacterial]] effects when tested against ''[[Mycobacterium aurum]]''.<ref name="Ingólfsdóttir et al. 1998"/><ref name="Honda et al. 2010"/> Recent (2021) research indicates that salazinic acid is a potent modulator of [[Nrf2]], [[NF-κB]] and [[STAT3]] [[cell signaling|signaling]] pathways in [[colorectal cancer]] cells.<ref name="Papierska et al. 2021"/>
The complete [[Proton NMR|<sup>1</sup>H]] and [[Carbon-13 nuclear magnetic resonance|<sup>13</sup>C NMR]] spectral assignments for salazinic acid were reported in 2000.<ref name="Eifler-Lima et al. 2000"/>
==Occurrence== {{multiple image | align = right | total_width = 320 | image1 = Parmotrema stuppeum - Flickr - pellaea.jpg | caption1 = | image2 = Parmotrema subisidiosum (4504575802).jpg | caption2 = | footer = ''[[Parmotrema stuppeum]]'' (left) and ''[[Parmotrema subisidiosum]]'' (right) are two [[foliose lichen]]s that contain salazinic acid.<ref name="Spielmann & Marcelli 2020"/> }} Salazinic acid is derived via the [[acetyl polymalonyl pathway]], a [[metabolic pathway]] that uses [[acetyl-CoA]] and [[malonyl-CoA]] (derivatives of [[coenzyme A]]). The compound is common in the large lichen genus ''[[Parmotrema]]'', and plays an important role in the [[chemotaxonomy]] and [[systematics]] of that genus. A 2020 revision included 66 salazinic acid-containing species.<ref name="Spielmann & Marcelli 2020"/> The presence or absence of the compound is also important in the classification of genus ''[[Bulbothrix]]''.<ref name="Benatti 2012"/><ref name="Benatti 2012b"/>
In nature, salazinic acid serves as an [[antioxidant]] as well as a [[photoprotection|photoprotectant]], helping the lichen to survive in conditions of both [[abiotic stress|abiotic]] and [[biotic stress]]. A study of three [[foliose lichen]] species showed higher quantities of salazinic acid correlating with increases in altitude.<ref name="Shukla et al. 2015"/> An earlier study demonstrated other possible effects of environmental conditions on salazinic acid content. It was shown that the salazinic acid content of ''[[Ramalina siliquosa]]'' is higher where the annual mean temperature is higher, and the content of the lichens growing on the dark-coloured rock or on the southern rock face is higher than that of the lichens growing on the light-coloured rock or on the northern rock face.<ref name="Hamada 1982"/>
==Related compounds==
The depsidones [[chalybaeizanic acid]] and [[quaesitic acid]], isolated from the lichens ''[[Xanthoparmelia amphixanthoides]]'' and ''[[Hypotrachyna quaesita]]'', respectively, are [[chemical structure|structurally]] similar to salazinic acid.<ref name="Elix & Wardlaw 1999"/> In consalazinic acid, the [[aldehyde]] group of salazinic acid is replaced with a [[benzyl alcohol]] functional group.<ref name="O'Donovan et al. 1980"/>
8'-''O''-Methylsalazinic acid was isolated from ''[[Parmotrema dilatatum]]''.<ref name="Devi et al. 2020"/> Several new synthesised derivatives of salazinic acid were reported in 2021 using [[bromination]], [[nucleophilic addition]], [[Friedel-Crafts alkylation]], and [[esterification]].<ref name="Pham et al. 2022"/>
==Eponyms== Several authors have explicitly named salazinic acid in the [[botanical name|specific epithet]]s of their published lichen species, thereby acknowledging the presence of this compound as an important [[taxonomy (biology)|taxonomic]] characteristic. These [[eponym]]s are listed here, followed by their [[Author citation (botany)|taxonomic authority]] and year of publication: * ''[[Acanthothecis salazinica]]'' {{small|van den Boom & Sipman (2013)}}<ref name="van den Boom & Sipman 2013"/> * ''[[Bryoria salazinica]]'' {{small|[[Irwin Brodo|Brodo]] & [[D.Hawksw.]] (1977)}}<ref name="Brodo & Hawksworth 1977"/> * ''[[Graphina salazinica]]'' {{small|[[A.W.Archer]] (2001)}}<ref name="Archer 2001"/> * ''[[Karoowia salazinica]]'' {{small|[[Mason Hale|Hale]] (1989)}}<ref name="Hale 1989"/> * ''[[Lepraria salazinica]]'' {{small|Tønsberg (2007)}}<ref name="Tønsberg 2007"/> * ''[[Myelochroa salazinica]]'' {{small|Sheng L.Wang, J.B.Chen & [[John Alan Elix|Elix]] (2001)}}<ref name="Wang et al. 2001"/> * ''[[Ocellularia salazinica]]'' {{small|Papong, Mangold & Lücking (2014)}}<ref name="Papong et al. 2014"/> * ''[[Pertusaria salazinica]]'' {{small|A.W.Archer & Elix (2017)}}<ref name="Archer & Elix 2017"/> * ''[[Phaeographina salazinica]]'' {{small|A.W.Archer (2003)}}<ref name="Archer 2003"/> * ''[[Psiloparmelia salazinica]]'' {{small|Elix & [[T.H.Nash]] (1992)}}<ref name="Elix & Nash 1992"/> * ''[[Diorygma salazinicum]]'' {{small|Sutjar. & [[Klaus Kalb|Kalb]] (2014)}}<ref name="Sutjaritturakan et al. 2014"/> * ''[[Oropogon salazinicus]]'' {{small|Essl. (1989)}}<ref name="Esslinger 1989"/>
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<ref name="Papierska et al. 2021">{{cite journal |last1=Papierska |first1=Katarzyna |last2=Krajka-Kuźniak |first2=Violetta |last3=Paluszczak |first3=Jarosław |last4=Kleszcz |first4=Robert |last5=Skalski |first5=Marcin |last6=Studzińska-Sroka |first6=Elżbieta |last7=Baer-Dubowska |first7=Wanda |title=Lichen-derived depsides and depsidones modulate the Nrf2, NF-κB and STAT3 signaling pathways in colorectal cancer cells |journal=Molecules |volume=26 |issue=16 |year=2021 |doi=10.3390/molecules26164787 |page=4787 |pmid=34443375 |pmc=8400444 |doi-access=free}}</ref>
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<ref name="Pham et al. 2022">{{cite journal |last1=Pham |first1=Nguyen-Kim-Tuyen |last2=Tran |first2=Nguyen-Minh-An |last3=Truong Nguyen |first3=Huy |last4=Pham |first4=Duc-Dung |last5=Nguyen |first5=Thi-Quynh-Trang |last6=Nguyen |first6=Thi-Hong-Anh |last7=Nguyen |first7=Huu-Tri |last8=Do |first8=Thanh-Hung |last9=Nguyen |first9=Ngoc-Hong |last10=Duong |first10=Thuc-Huy |title=Design, modification, and bio-evaluation of salazinic acid derivatives |journal=Arabian Journal of Chemistry |volume=15 |issue=1 |year=2022 |doi=10.1016/j.arabjc.2021.103535 |article-number=103535 |doi-access=free}}</ref>
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}}
[[Category:Lactones]] [[Category:Lichen products]] [[Category:Heterocyclic compounds with 4 rings]] [[Category:Hydroxymethyl compounds]] [[Category:Polyphenols]] [[Category:Benzodioxepines]] [[Category:Tetrols]] [[Category:Primary alcohols]] [[Category:Secondary alcohols]]