Barbatic acid
Names
IUPAC name
2-Hydroxy-4-(2-hydroxy-4-methoxy-3,6-dimethylbenzoyl)oxy-3,6-dimethylbenzoic acid
Other names
Barbatinic acid
Identifiers
3D model (JSmol)
ChEBI
  • InChI=1S/C19H20O7/c1-8-7-13(11(4)16(20)14(8)18(22)23)26-19(24)15-9(2)6-12(25-5)10(3)17(15)21/h6-7,20-21H,1-5H3,(H,22,23)
    Key: NMKBRSYSHBPUPY-UHFFFAOYSA-N
  • CC1=CC(=C(C(=C1C(=O)OC2=C(C(=C(C(=C2)C)C(=O)O)O)C)O)C)OC
Properties
C19H20O7
Molar mass 360.362 g·mol−1
Melting point 187 °C (369 °F; 460 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Barbatic acid is an organic compound that is made by some lichens. It is in the structural class known as depsides. It is particularly common in the genera Usnea (the beard lichens) and Cladonia.

History

The compound was first isolated in 1880 from the lichen Usnea barbata by chemists John Stenhouse and Charles Groves.[1][2][3] The compound coccellic acid, isolated from Cladonia coccifera, was later shown to be the same compound as barbatic acid.[4]

Properties

Biosynthetically, barbatic acid is made of two units of orsellinate derivatives that are created by an aromatic synthase enzyme. The repeated action of this enzyme produces an 8-carbon polyketide intermediate that is cyclized.

Barbatic acid's IUPAC name is 2-hydroxy-4-(2-hydroxy-4-methoxy-3,6-dimethylbenzoyl)oxy-3,6-dimethylbenzoic acid. Its chemical formula is C19H20O7; it has a molecular mass of 360.36 grams per mole. In its purified crystalline form, it exists as various forms: small rhombic prisms, long needles, or delicate thin sheets (lamellae). Its melting point is 187 °C (369 °F).[5]

The crystal structure of the methyl ester of barbatic acid (i.e., methyl 2-hydroxy-4-(2-hydrocy-4-methoxy-3,6-dimethylbenzoyloxy)-3,6-dimethylbenzoate, or barbatin) has been characterised. It is in the triclinic crystal system, in the space group called P1. In this crystal form, two highly substituted phenyl rings are bridged by an ester group and are inclined towards each other at 106.1°. There are two strong intramolecular hydrogen bonds between the hydroxyl substituents an the adjacent ester carbonyl groups.[6] The crystal structure of pure barbatic acid, determined using single crystal X-ray diffraction analysis, was reported in 2019.[7]

Synthesis

A synthesis for barbatic acid was reported in 1975 using trifluoroacetic acid as a condensing agent.[8] In 2022, a total synthesis was reported; the eight-step procedure starts with commercially available methyl atrarate, producing barbatic acid in a 22% total yield.[9]

A high-performance liquid chromatography (HPLC) technique has been adapted to couple the HPLC output with a photodiode array detector to screen for lichen products based on their specific ultraviolet–visible spectra. In this way, barbatic acid is detected by monitoring its retention time, and verifying the presence of three peaks representing wavelengths of maximum absorption (λmax) at 214, 276, and 310 nm.[10]

Research

Some preliminary research suggests that based on the in vitro molluscicidal activity of barbatic acid against the human parasite Schistosoma mansoni, it may have potential use in the large-scale control and/or eradication of schistosomiasis.[11] Other research has shown that it is non-toxic to human peripheral blood mononuclear cells at concentrations that are effective against the parasite.[12] Barbatic acid inhibits photosynthesis by irreversible binding to the proteins in the photosystem II complex.[13][14]

Immobilised cells of the lichen Cladonia miniata var. parvipes have been used to synthesise barbatic acid. The cells were given sodium acetate or calcium acetate as a precursor for phenol biosynthesis.[15]

Laboratory experiments have demonstrated that barbatic acid has some antioxidant and antimicrobial activity.[16] It has cytotoxic and genotoxic activity against some tumour cell lines.[7] And in vitro and in vivo experiments using various cancer cell lines suggest that barbatic acid has antineoplastic and pro-apoptotic activities combined with a low toxicity.[7]

References

  1. ↑ Stenhouse, John; Groves, Charles E. (1880). "Beiträge zur Geschichte der Orcine: Betorcinol und einige seiner Derivate". Justus Liebig's Annalen der Chemie (in German). 203 (3): 285–305. doi:10.1002/jlac.18802030304.
  2. ↑ Stenhouse, John; Groves, Charles E. (1880). "XXII.—Contributions to the history of the orcins. Betorcinol and some of its derivatives". Journal of the Chemical Society, Transactions. 37: 395–407. doi:10.1039/ct8803700395.
  3. ↑ Robertson, Alexander; Stephenson, Richard John (1932). "222. Lichen acids. Part III. The constitution of barbatic acid and the syntheses of isorhizonic acid and methyl barbatate". Journal of the Chemical Society (Resumed): 1675. doi:10.1039/jr9320001675.
  4. ↑ Asahina, Yasuhiko; Fuzikawa, Fukuziro (1934). "Untersuchungen über Flechtenstoffe, XLV. Mitteil.: Über die Identität der Coccellsäure mit der Barbatinsäure". Berichte der Deutschen Chemischen Gesellschaft (A and B Series). 67 (11): 1793–1795. doi:10.1002/cber.19340671103.
  5. ↑ Huneck, Siegfried (1996). Identification of Lichen Substances. Berlin, Heidelberg: Springer Berlin Heidelberg. pp. 48, 117, 239. ISBN 978-3-642-85245-9. OCLC 851387266.
  6. ↑ Stoeckli-Evans, H.; Blaser, D. (1991). "Structure of the methyl esters of barbatic and evernic acids: natural para-depsides". Acta Crystallographica Section C Crystal Structure Communications. 47 (12): 2620–2624. doi:10.1107/s0108270191006340.
  7. 1 2 3 Reddy, S. Divya; Siva, Bandi; Kumar, Katragunta; Babu, V.S. Phani; Sravanthi, Vemireddy; Boustie, Joel; Nayak, V. Lakshma; Tiwari, Ashok K.; Rao, CH. V.; Sridhar, B.; Shashikala, P.; Babu, K. Suresh (2019). "Comprehensive analysis of secondary metabolites in Usnea longissima (lichenized ascomycetes, Parmeliaceae) using UPLC-ESI-QTOF-MS/MS and pro-apoptotic activity of barbatic acid". Molecules. 24 (12): e2270. doi:10.3390/molecules24122270. PMC 6630668. PMID 31216770.
  8. ↑ Elix, John A.; Norfolk, Susan (1975). "Synthesis of para-β-orcinol depsides". Australian Journal of Chemistry. 28 (5): 1113–1124. doi:10.1071/ch9751113.
  9. ↑ Yu, Xiang; Xi, Yin-Kai; Luo, Guo-Yong; Long, Yi; Yang, Wu-De (3 January 2022). "Synthesis of barbatic acid". Journal of Asian Natural Products Research. 24 (12): 1150–1156. doi:10.1080/10286020.2021.2023506. PMID 34978467. S2CID 245651506.
  10. ↑ Yoshimura, Isao; Kinoshita, Yasuhiro; Yamamoto, Yoshikazu; Huneck, Siegfried; Yamada, Yasuyuki (1994). "Analysis of secondary metabolites from lichen by high-performance liquid chromatography with a photodiode array detector". Phytochemical Analysis. 5 (4): 197–205. doi:10.1002/PCA.2800050405.
  11. ↑ Martins, Mônica; Silva, Monique; Silva, Hianna; Silva, Luanna; Albuquerque, Mônica; Aires, André; Falcão, Emerson; Pereira, Eugênia; de Melo, Ana; da Silva, Nicácio (2017). "Barbatic acid offers a new possibility for control of Biomphalaria glabrata and schistosomiasis". Molecules. 22 (4): 568. doi:10.3390/molecules22040568. PMC 6154637. PMID 28362351.
  12. ↑ Silva, H.A.M.F.; Aires, A.L.; Soares, C.L.R.; Sá, J.L.F.; Martins, M.C.B.; Albuquerque, M.C.P.A.; Silva, T.G.; Brayner, F.A.; Alves, L.C.; Melo, A.M.M.A.; Silva, N.H. (2020). "Barbatic acid from Cladia aggregata (lichen): Cytotoxicity and in vitro schistosomicidal evaluation and ultrastructural analysis against adult worms of Schistosoma mansoni". Toxicology in Vitro. 65: 104771. doi:10.1016/j.tiv.2020.104771. PMID 31935486. S2CID 210827117.
  13. ↑ Endo, Tsuyoshi; Takahagi, Toshikazu; Kinoshita, Yasuhiro; Yamamoto, Yoshikazu; Sato, Fumihiko (1998). "Inhibition of photosystem II of spinach by lichen-derived Depsides". Bioscience, Biotechnology, and Biochemistry. 62 (10): 2023–2027. doi:10.1271/bbb.62.2023. PMID 27385453.
  14. ↑ Takahagi, Toshikazu; Ikezawa, Nobuhiro; Endo, Tsuyoshi; Ifuku, Kentaro; Yamamoto, Yoshikazu; Kinoshita, Yasuhiro; Takeshita, Shunji; Sato, Fumihiko (2006). "Inhibition of PSII in atrazine-tolerant tobacco cells by barbatic acid, a lichen-derived depside". Bioscience, Biotechnology, and Biochemistry. 70 (1): 266–268. doi:10.1271/bbb.70.266. PMID 16428846. S2CID 13291222.
  15. ↑ Vivas, Mercedes; Millanes, Ana Maria; Filho Neli K., Lauro Xavier; Honda, Eugênia C.; Pereira, Carlos Vicente; Legaz, Maria-Estrella (2006). "Production of barbatic acid by immobilized cells of Cladonia miniata var. parvipes in calcium alginate". Journal of the Hattori Botanical Laboratory. 100: 855–863.
  16. ↑ Martins, Mônica Cristina Barroso; Lima, Marcio James Gonçalves de; Silva, Flávia Pereira; Azevedo-Ximenes, Eulália; Silva, Nicácio Henrique da; Pereira, Eugênia Cristina (2010). "Cladia aggregata (lichen) from Brazilian northeast: chemical characterization and antimicrobial activity". Brazilian Archives of Biology and Technology. 53 (1): 115–122. doi:10.1590/s1516-89132010000100015.
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