Lichens, polyketide production

Lichens had to evolve diverse biosynthetic pathways to produce such complex arrays of secondary metabolites polyketide, shikimic acid, and mevalonic acid pathways. Most of the lichen substances are phenolic compounds. Polyketide-derived aromatic compounds, depsides, depsidones, dibenzofurans, xanthones, and naphthoquinones, are of great interest. Compounds from other pathways are esters, terpenes, steroids, terphenylquinones, and pulvinic acid (Fahselt 1994 Cohen and Towers 1995 Muller 2001 Brunauer et al. 2006, 2007 Stocker-Worgotter and Elix 2002 Johnson et al. 2011 Manojlovic et al. 2012). So, many lichens and lichen products have proved to be a source of important secondary metabolites for food and pharmaceutical industries (Huneck 1999 Oksanen 2006)... 

Bruun and Motzfeld (35) isolated the novel peroxyergosteryl divari-catinate (525) from the lichen Haematomma ventosum. This product is the only known example of a steryl ester of an aromatic polyketide derived acid. The depside divaricatic acid (234) also present in this lichen contains the same A-ring component and it is possible that the ester formation in both of these metabolites is effected by the same enzyme. 

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