Lichen acids stictic acid

Depsides, tridepsides, and tetradepsides consist of two, three, and four hydroxybenzoic acid residues linked by ester groups. These are the most numerous classes of secondary metabolites in lichens. More than one hundred Uchen compounds are depsidones, which have an additional ether bond between aromatic rings. Depsidones in Uchen are believed to arise by oxidative cycUzation of depsides. It has been found that depsidone and depside compounds such as atranorin, divaricatic acid, lecanoric acid, evemic acid, salazinic acid, physodic acid, and stictic acid possess important antimicrobial activity (Manojlovic et al. 2012 Kosanic et al. 2013, 2014a Rankovic et al. 2014). 

Atalay et al. (2011) determined the lipid peroxidation inhibition potential for nine lichen compounds in two lipid peroxidation test systems (liposome and emulsion systems). They found that isidiophorin, rhizonaldehyde, rhizonyl alcohol and pulmonarianin retarded lipid peroxidation at in both test systems. However, stictic acid and ergosterol peroxide exhibited antioxidant activity in only the liposome test system. Usnic acid and diffractaic acid were not antioxidants in either system, while stictic acid was not lipid peroxidation inhibitor in the emulsion test system. All compounds, which inhibited lipid peroxidation in both test systems, were also DPPH radical scavengers. 

Lohezic-Le Devehat F, Tomasi S, Elix JA et al (2007) Stictic acid dtaivatives frinn the lichen Usnea articulate and their antioxidant activities. J Nat Prod 70 1218-1220 Lopes TIB, Coelho RG, Yoshida NC et al (2008) Radical scavenging activity of oisellinates. Chem Pharm Bull 56 1551-1554... 

Pejin B, lodice C, Bogdanovic G et ai (2013) Stictic acid inhibits ceil growth of human colon adenocarcinoma HT-29 ceils. Arab J Chem. doi 10.1016/j.arabjc.2013.03.003 Rankovic BR, Kosanic MM, Stanojkovic TP (2011) Antioxidant, antimicrobial and anticancer activity of the lichens Cladoniafurcata, Lecanora atra and Lecanora muralis. BMC Complement Altem Med 11 97... 

Whiton and Lawrey found that ascospore germination of the lichens Cladonia cristatella 724), Graphis scripta and Caloplaca citrina 725) was much reduced in the presence of lichen substances. Spore germination of Cladonia cristatella and Caloplaca citrina was inhibited by vulpinic acid, evernic acid and atranorin respectively stictic acid showed no activity. 

Allergenic Activity. Numerous lichen substances like atranorin, barbatic, diffractaic, evernic, fumarprotocetraric, lobaric, per-latolic, physodic, physodalic, protolichesterinic, salazinic, stictic and usnic acids are allergenes (Brasch and Jacobsen 1991). 

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