A new series of azaphilone pigments named atrorosins have been isolated from the filamentous fungus Talaromyces atroroseus. Atrorosins have a similar azaphilone scaffold as the orange Monascus pigment PP-O, with a carboxylic acid group at C-1, but are unique by their incorporation of amino acids into the isochromene system. Despite that the atrorosin precursor PP-O, during fermentation, was initially produced as two isomers (3:2, cis:trans ratio), the atrorosins were surprisingly almost exclusively (99.5%) produced as the cis-form, possibly due to steric interactions with the incorporated amino acid. When grown on complex media, a whole range of atrorosins is produced, whereas individual atrorosins can be produced selectively during fermentation by supplementing with the desired primary amine-containing compound.
Keywords: Azaphilone; Monascus pigments; Structural elucidation; Talaromyces.