# Hypostictic acid

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Lichen-derived depsidone

Hypostictic acid Names IUPAC name 13,17-dihydroxy-5-methoxy-4,7,12-trimethyl-2,10,16-trioxatetracyclo[9.7.0.03,8.014,18]octadeca-1(11),3(8),4,6,12,14(18)-hexaene-9,15-dione Other names Hypostictinsäure Identifiers CAS Number 68729-11-3 3D model (JSmol) Interactive image ChemSpider 131911187 PubChem CID 101351294 InChI InChI=1S/C19H16O8/c1-6-5-9(24-4)7(2)14-10(6)17(21)26-15-8(3)13(20)11-12(16(15)25-14)19(23)27-18(11)22/h5,19-20,23H,1-4H3 Key: PGRWVCGZKIXMQW-UHFFFAOYSA-N SMILES CC1=CC(=C(C2=C1C(=O)OC3=C(O2)C4=C(C(=C3C)O)C(=O)OC4O)C)OC Properties Chemical formula C19H16O8 Molar mass 372.3 g·mol−1 Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Chemical compound

**Hypostictic acid** is a lichen [secondary metabolite](/source/Secondary_metabolite) belonging to the [depsidone](/source/Depsidone) class of [aromatic compounds](/source/Aromatic_compound). It was first prepared in 1933 by [catalytic hydrogenation](/source/Catalytic_hydrogenation) of [stictic acid](/source/Stictic_acid) isolated from the [foliose](/source/Foliose_lichen) lichen *[Lobaria pulmonaria](/source/Lobaria_pulmonaria)*, and as a natural product was later reported from an undescribed species of the [crustose](/source/Crustose_lichen) lichen genus *[Thelotrema](/source/Thelotrema)* collected in Venezuelan [cloud forest](/source/Cloud_forest). As a [lichen metabolite](/source/Lichen_product) it has been detected as a minor or trace component in several foliose and crustose lichen genera, including *[Pseudoparmelia](/source/Pseudoparmelia)*, *[Xanthoparmelia](/source/Xanthoparmelia)*, *[Nephroma](/source/Nephroma)*, *[Aspicilia](/source/Aspicilia)*, *[Clandestinotrema](/source/Clandestinotrema)*, *[Porpidia](/source/Porpidia)* and *[Rinodina](/source/Rinodina)*. Hypostictic acid forms colourless crystals with a relatively high [melting point](/source/Melting_point) and has been used as a model substrate in [electrochemical](/source/Electrochemistry) studies that investigate the [reduction](/source/Redox) behaviour of lichen depsidones.

## History and synthesis

Before its discovery as a [lichen metabolite](/source/Lichen_product), the compound now known as hypostictic acid was obtained only as a reduction product of [stictic acid](/source/Stictic_acid) (*Stictinsäure*). In 1933 [Yasuhiko Asahina](/source/Yasuhiko_Asahina) and co-workers reduced stictic acid (*Stictinsäure*) from *[Lobaria pulmonaria](/source/Lobaria_pulmonaria)* with hydrogen in [glacial acetic acid](/source/Glacial_acetic_acid) using [palladium on carbon](/source/Palladium_on_carbon) as catalyst, giving a C19H16O8 depsidone that crystallised as colourless needles decomposing at 263–264 °C.[1] They characterised this compound by elemental analysis, [methoxy](/source/Methoxy) determinations and conversion into a [dimethyl ether](/source/Dimethyl_ether), and from the relationship of its [methylated](/source/Methylation) reduction products to those of [salazinic acid](/source/Salazinic_acid) concluded that stictic acid is a monomethyl ether of desoxysalazinic acid.[1] Later work showed that this reduction product is identical with naturally occurring hypostictic acid isolated from lichens.[2]

## Occurrence

Hypostictic acid was first isolated from the [foliose lichen](/source/Foliose_lichen) species *[Lobaria pulmonaria](/source/Lobaria_pulmonaria)*.

Hypostictic acid has been detected in several [lichens](/source/Lichen), particularly in members of the family [Parmeliaceae](/source/Parmeliaceae). As a natural product it was first isolated from a new species of the [crustose lichen](/source/Crustose_lichen) genus *[Thelotrema](/source/Thelotrema)* (family [Graphidaceae](/source/Graphidaceae)) collected in [cloud forest](/source/Cloud_forest) at about 2,300 m elevation in the San Eusebio region of [Mérida State](/source/M%C3%A9rida_(state)), Venezuela.[2] In the foliose lichen *[Xanthoparmelia quintaria](https://en.wikipedia.org/w/index.php?title=Xanthoparmelia_quintaria&action=edit&redlink=1)*, a South African [endemic](/source/Endemic), [thin-layer chromatography](/source/Thin-layer_chromatography) was used to show that hypostictic acid corresponds to [Culberson](/source/William_Louis_Culberson)'s previously unnamed compound "PQ1" and co-occurs with hyposalazinic acid ("PQ2").[2]

Hypostictic acid occurs as a minor chemical component in *[Pseudoparmelia sphaerospora](https://en.wikipedia.org/w/index.php?title=Pseudoparmelia_sphaerospora&action=edit&redlink=1)*,[3] *[Nephroma australae](https://en.wikipedia.org/w/index.php?title=Nephroma_australae&action=edit&redlink=1)*,[4] and has been reported from *[Xanthoparmelia](/source/Xanthoparmelia)* species where it is usually present only in trace amounts.[5] It has also been recorded from crustose lichen species in the genera *[Aspicilia](/source/Aspicilia)*,[6] *[Clandestinotrema](/source/Clandestinotrema)*,[7] *[Porpidia](/source/Porpidia)*,[8] and *[Rinodina](/source/Rinodina)*.[9]

## Chemical properties

Hypostictic acid is a lichen depsidone with the [molecular formula](/source/Molecular_formula) C19H16O8 (relative [molecular mass](/source/Molecular_mass) 372.32). It crystallises from [acetone](/source/Acetone) as colourless needles and has a [melting point](/source/Melting_point) of about 263–264 °C, decomposing on heating.[1][10] In [infrared spectra](/source/Infrared_spectroscopy) it shows strong [absorption bands](/source/Absorption_band) around 1,695 and 1,750 cm−1, in the region expected for conjugated carbonyl groups, together with bands attributable to aromatic and phenolic functions. Proton [NMR spectra](/source/Nuclear_magnetic_resonance_spectroscopy) in [pyridine](/source/Pyridine)-d5 display three singlet [methyl](/source/Methyl) signals, a methoxy group and two aromatic protons, consistent with a heavily substituted aromatic framework. In the [mass spectrum](/source/Mass_spectrometry) hypostictic acid gives a molecular ion peak at m/z 372 with a characteristic series of fragment ions. Acetylation with [acetic anhydride](/source/Acetic_anhydride) in [pyridine](/source/Pyridine) yields the diacetate, diacetylhypostictic acid, which forms crystals melting at about 244 °C and is used as a [derivative](/source/Derivative_(chemistry)) for further analytical work.[10]

[Electrochemical](/source/Electrochemistry) studies in dry [dimethylformamide](/source/Dimethylformamide) (DMF) using a glassy carbon working [electrode](/source/Electrode) have examined hypostictic acid as a model lichen depsidone. In this medium the neutral molecule undergoes an irreversible one-electron [reduction](/source/Redox) to a [radical anion](/source/Radical_anion), followed by [cleavage](/source/Bond_cleavage), [disproportionation](/source/Disproportionation) and a self-[protonation](/source/Protonation) step that give the reduced depsidone hypostictinolide. Prolonged controlled-potential [electrolysis](/source/Electrolysis) leads to further transformation of hypostictinolide into two additional derivatives, including a ring-opened depside and an [aldehyde](/source/Aldehyde)-bearing dibenzodioxepine, whose structures were assigned using high-resolution [mass spectrometry](/source/Mass_spectrometry) together with one- and two-dimensional [NMR spectroscopy](/source/NMR_spectroscopy).[11]

## References

1. ^ [***a***](#cite_ref-Asahina_et_al._1933_1-0) [***b***](#cite_ref-Asahina_et_al._1933_1-1) [***c***](#cite_ref-Asahina_et_al._1933_1-2) Asahina, Yasuhiko; Yanagita, Masaiti; Omaki, Tatuo (1933). "Untersuchungen über Flechtenstoffe, XXV. Mitteil.: Über Stictinsäure". *Berichte der Deutschen Chemischen Gesellschaft (A and B Series)* (in German). **66** (7): 943–947. [doi](/source/Doi_(identifier)):[10.1002/cber.19330660706](https://doi.org/10.1002%2Fcber.19330660706).

1. ^ [***a***](#cite_ref-Keogh_1978_2-0) [***b***](#cite_ref-Keogh_1978_2-1) [***c***](#cite_ref-Keogh_1978_2-2) Keogh, Myles F. (1978). "New β-orcinol depsidones from *Xanthoparmelia quintaria* and a *Thelotrema* species". *Phytochemistry*. **17** (7): 1192–1193. [Bibcode](/source/Bibcode_(identifier)):[1978PChem..17.1192K](https://ui.adsabs.harvard.edu/abs/1978PChem..17.1192K). [doi](/source/Doi_(identifier)):[10.1016/S0031-9422(00)94315-2](https://doi.org/10.1016%2FS0031-9422%2800%2994315-2).

1. **[^](#cite_ref-White_et_al._2014_3-0)** White, Pollyanna; Oliveira, Rita; Oliveira, Aldeidia; Serafini, Mairim; Araújo, Adriano; Gelain, Daniel; Moreira, Jose; Almeida, Jackson; Quintans, Jullyana; Quintans-Junior, Lucindo; Santos, Marcio (2014). ["Antioxidant activity and mechanisms of action of natural compounds isolated from lichens: a systematic review"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6271897). *Molecules*. **19** (9): 14496–14527. [doi](/source/Doi_(identifier)):[10.3390/molecules190914496](https://doi.org/10.3390%2Fmolecules190914496). [PMC](/source/PMC_(identifier)) [6271897](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6271897). [PMID](/source/PMID_(identifier)) [25221871](https://pubmed.ncbi.nlm.nih.gov/25221871).

1. **[^](#cite_ref-Moroney_et_al._1981_4-0)** Moroney, Simon E.; Ronaldson, Kathlyn J.; Wilkins, Alistair L.; Green, T.G. Allan; James, P.W. (1981). "Depsidone constituents from the quintaria group of *Nephroma* species". *Phytochemistry*. **20** (4): 787–789. [Bibcode](/source/Bibcode_(identifier)):[1981PChem..20..787M](https://ui.adsabs.harvard.edu/abs/1981PChem..20..787M). [doi](/source/Doi_(identifier)):[10.1016/0031-9422(81)85175-8](https://doi.org/10.1016%2F0031-9422%2881%2985175-8).

1. **[^](#cite_ref-Elix_1981_5-0)** Elix, J.A. (1981). "New species of *Parmelia* subgen. *Xanthoparmelia* (lichens) from Australia and New Zealand". *Australian Journal of Botany*. **29** (3): 349–376. [Bibcode](/source/Bibcode_(identifier)):[1981AuJB...29..349E](https://ui.adsabs.harvard.edu/abs/1981AuJB...29..349E). [doi](/source/Doi_(identifier)):[10.1071/BT9810349](https://doi.org/10.1071%2FBT9810349).

1. **[^](#cite_ref-Fryday_et_al._2021_6-0)** Fryday, Alan M.; Wheeler, Timothy B.; Etayo, Javier (2021). ["A new species of *Aspicilia* (Megasporaceae), with a new lichenicolous *Sagediopsis* (Adelococcaceae), from the Falkland Islands"](https://doi.org/10.1017%2FS0024282921000244). *The Lichenologist*. **53** (4): 307–315. [Bibcode](/source/Bibcode_(identifier)):[2021ThLic..53..307F](https://ui.adsabs.harvard.edu/abs/2021ThLic..53..307F). [doi](/source/Doi_(identifier)):[10.1017/S0024282921000244](https://doi.org/10.1017%2FS0024282921000244).

1. **[^](#cite_ref-Medeiros_2018_7-0)** Medeiros, Ian D. (2018). ["A new species of *Clandestinotrema* (Ascomycota: Ostropales: Graphidaceae) from montane cloud forest in the Venezuelan Andes"](https://doi.org/10.2478%2Fpfs-2018-0002). *Plant and Fungal Systematics*. **63** (1): 7–10. [doi](/source/Doi_(identifier)):[10.2478/pfs-2018-0002](https://doi.org/10.2478%2Fpfs-2018-0002).

1. **[^](#cite_ref-Zhao_et_al._2016_8-0)** Zhao, Xiang-Xiang; Zhang, Lu-Lu; Miao, Cong-Cong; Zhao, Zun-Tian (2016). "A new species of *Porpidia* from China". *The Lichenologist*. **48** (3): 229–235. [Bibcode](/source/Bibcode_(identifier)):[2016ThLic..48..229Z](https://ui.adsabs.harvard.edu/abs/2016ThLic..48..229Z). [doi](/source/Doi_(identifier)):[10.1017/S0024282916000128](https://doi.org/10.1017%2FS0024282916000128).

1. **[^](#cite_ref-Giralt_&_Matzer_1994_9-0)** Giralt, Mireia; Matzer, Mario (1994). "The corticolous species of the genus *Rinodina* with biatorine or lecideine apothecia in southern Europe and Macaronesia". *The Lichenologist*. **26** (4): 319–332. [Bibcode](/source/Bibcode_(identifier)):[1994ThLic..26..319G](https://ui.adsabs.harvard.edu/abs/1994ThLic..26..319G). [doi](/source/Doi_(identifier)):[10.1006/lich.1994.1026](https://doi.org/10.1006%2Flich.1994.1026).

1. ^ [***a***](#cite_ref-Huneck_1996_10-0) [***b***](#cite_ref-Huneck_1996_10-1) Huneck, Siegfried (1996). *Identification of Lichen Substances*. Berlin, Heidelberg: Springer Berlin Heidelberg. pp. 332–333. [ISBN](/source/ISBN_(identifier)) [978-3-642-85245-9](https://en.wikipedia.org/wiki/Special:BookSources/978-3-642-85245-9). [OCLC](/source/OCLC_(identifier)) [851387266](https://search.worldcat.org/oclc/851387266).

1. **[^](#cite_ref-Carvalho_et_al._2004_11-0)** Carvalho, Adriana E.; Barison, Andersson; Honda, Neli K.; Gilberto Ferreira, Antonio; Maia, Gilberto (2004). "Two new compounds from the electroreduction of hypostictic acid". *Journal of Electroanalytical Chemistry*. **572** (1): 1–14. [doi](/source/Doi_(identifier)):[10.1016/j.jelechem.2004.05.019](https://doi.org/10.1016%2Fj.jelechem.2004.05.019).

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Adapted from the Wikipedia article [Hypostictic acid](https://en.wikipedia.org/wiki/Hypostictic_acid) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Hypostictic_acid?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.