Subpsoromic acid
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| IUPAC name
10-formyl-9-hydroxy-3-methoxy-7-methyl-6-oxobenzo[b][1,4]benzodioxepine-1-carboxylic acid[1]
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Other names
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3D model (JSmol)
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| ChEBI | |
| ChemSpider | |
PubChem CID
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| Properties | |
| C17H12O8 | |
| Molar mass | 344.275 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Subpsoromic acid is a depsidone with the molecular formula C17H12O8 that was originally isolated from the lichen species Ocellularia praestans. It belongs to a small subclass of depsidones that combine a β-orcinol A-ring with an orcinol B-ring; few other natural products share that architectural motif.[2]
Natural occurrence and isolation
[edit]The compound was discovered during a thin-layer chromatographic survey of O. praestans thalli collected on tree bark in Brazil's coastal Restinga forest . Soxhlet extraction of 0.39 g of dried material with anhydrous diethyl ether, followed by preparative-layer chromatography, yielded 2.4 mg of pure subpsoromic acid—about 0.6 % of the dry thallus mass. The product formed colourless crystals that decomposed above 350 °C, and its homogeneity was confirmed by high-performance liquid chromatography and proton nuclear magnetic resonance.[2] The compound has since been reported as a minor metabolite in Herpothallon rubroechinatum[3] and in Acanthothecis verrucosa.[4]
Structure and chemical properties
[edit]High-resolution mass spectrometry established the molecular formula and showed that subpsoromic acid contains one fewer methylene unit than the better-known psoromic acid. One- and two-dimensional NMR spectra revealed a single carbon-bound methyl group (δ 2.54 ppm), one methoxy group (δ 3.83 ppm), two meta-coupled aromatic protons, an aldehydic proton (δ 10.56 ppm), and a strongly chelated phenolic hydroxyl (δ 12.36 ppm). These data, together with diagnostic mass spectral fragments at m/z 179 and 177 arising from the A-ring, support the structure 4-formyl-3-hydroxy-8-methoxy-1-methyl-11-oxo-11H-dibenzo[b,e][1,4]dioxepin-6-carboxylic acid. The compound's thin-layer chromatography Rf values (0.34–0.38 in standard solvent systems) and HPLC retention index (RI 14; RT ≈ 21.6 min) further permit routine analytical identification.[2]
References
[edit]- ^ a b "Subpsoromic acid". Pubchem.ncbi.NLM.nih.gov.
- ^ a b c Elix, John A.; Wardlaw, Judith H.; Kalb, Klaus (2000). "Subpsoromic acid, a new depsidone from the lichen Ocellularia praestans". Australian Journal of Chemistry. 53 (9): 813. doi:10.1071/CH00113.
- ^ Frisch, Andreas; Thor, Göran; Elix, John (2010). "Herpothallon rubroechinatum (Arthoniaceae), a new species from tropical and subtropical America". The Bryologist. 113 (1): 144–148. doi:10.1639/0007-2745-113.1.144.
- ^ Joshi, Santosh; Upreti, Dalip K.; Thanh, Nguyen Thi; Nguyen, Anh Dong; Hur, Jae-Seoun (2017). "New and interesting species in the family Graphidaceae (Ascomycota: Ostropales ) from Vietnam". The Lichenologist. 49 (3): 259–268. doi:10.1017/S0024282917000172.