RESUMEN
Four so far unknown pyrroloquinoline alkaloids, yellow mycenaflavinsâ A, B, and C, and the purple mycenaflavinâ D, have been isolated from the fruiting bodies of Mycena haematopus. The structures of these new alkaloids were elucidated by NMR spectroscopy and HRMS (ESI+ ). The mycenaflavins are structurally related to mycenarubins and haematopodins, which have been previously identified in M. haematopus. However, compared with other known fungal pyrroloquinoline alkaloids, the mycenaflavins contain an additional double bond within the pyrroloquinoline moiety that accounts for the yellow colour of the monomeric mycenaflavinsâ A, B, and C. The purple mycenaflavinâ D is the first known dimeric pyrroloquinoline alkaloid with a C-C bridge between the two pyrroloquinoline units. Although the minor pyrroloquinoline alkaloid constituent mycenaflavinâ A exhibits only moderate bioactivity against the soil bacterium Azoarcus tolulyticus, the major pyrroloquinoline alkaloid constituent haematopodinâ B is similarly active as the antibiotic gentamicin.