Laetiporic acids, a family of non-carotenoid polyene pigments from fruit-bodies and liquid cultures of Laetiporus sulphureus (Polyporales, Fungi)

The non-isoprenoid polyene laetiporic acid A, recently described from fruit-bodies of the wood-rotting fungus Laetiporus sulphureus, was found to be the major orange pigment also in mycelium grown in liquid culture. Its formation was variable, ranging from 0.1 to 6.7 mg/g dry weight in three strains, all of which were identified as L. sulphureus by ITS rDNA sequence analysis. A second pigment, 2-dehydro-3-deoxylaetiporic acid A, is also described and fully characterized by NMR spectroscopy. Two further minor pigments, laetiporic acids B and C, were produced in liquid culture. These resemble laetiporic acid A but are enlarged by two and four carbon atoms, respectively, resulting in chromophores with I I or 12 instead of 10 conjugated double bonds as described for laetiporic acid A. Since fruit-bodies of L. sulphureus are edible, laetiporic acids might hold potential as food colourants.