Dryinones: Structure Elucidation of Red Colorants from Submerged Cultures of <i>Pleurotus dryinus</i>

Culture supernatants of the veiled oyster mushroom <i>Pleurotus dryinus</i> from the phylum Basidiomycota develop a deep burgundy-red coloration when supplemented with phenylalanine. This marks the first time that color formation for <i>P. dryinus</i>, a fungus that is ordinarily colorless, has been reported. The two main coloring secondary metabolites, named dryinones, were isolated, and their structures were elucidated by HR-ESI(+)-MS/MS, UV/vis, and multidimensional NMR spectroscopy. The colorants were structurally characterized as highly oxygenated meroterpenoids with an aminoquinone moiety as the main chromophore. The absolute configuration of the isolated dryinone A (<b>1</b>) was determined through NOESY correlations, ECD experiments, and DFT computations. These findings not only expand the chemical diversity of colorants within the phylum Basidiomycota but also demonstrate the biosynthetic versatility of <i>P. dryinus</i> under controlled culture conditions. The discovery of these aminoquinone-containing meroterpenoids provides new insights into fungal secondary metabolism and highlights the potential of edible mushrooms as underexplored sources of structurally unique natural products.