Xerocomorubin

Xerocomorubin is a pigment from the fungus order Boletales. It is the oxidized form of isoxerocomic acid. Air oxidation is responsible its formation, and it oxidizes faster to a similar pulvinic acid type pigment oxidized variant, variegatorubin. The long wavelength has an absorption at 497 nm, 106 nm higher than its precursor isoxerocomic acid. Synthesis experiments have shown tetra-acetylation by acetic anhydride and sulfuric acid. Although xerocomorubin and variegatorubin give off the same deep red color and could simultaneously occur in a mushroom, extracts from the deep red colored mushroom Boletus rubellus Krombh. identified only variegatorubin by thin layer chromatography (TLC), leading to the question the natural abundance of xerocomorubin.