Chromogenic triterpenoids from Cortinarius fulvoincarnatus, C-sodagnitus and related toadstools (Agaricales)

Fruit-bodies of the toadstools Cortinarius sodagnitus, C. fulvoincarnatus, C. arcuatorum (Agaricales) show a remarkable ink-red colour reaction when t reated with aqueous base. We isolated six chromogens, named the sodagnitins A-F, from the toadstools and elucidated their structures by spectroscopic techniques. The sodagnitins are triterpenoids of the malabaricane type with a highly modified side chain. A mechanism for the colour reaction is propo sed.