Mycenaflavin A, B, C, and D: Pyrroloquinoline Alkaloids from the Fruiting Bodies of the Mushroom Mycena haematopus

Abstract

Four so far unknown pyrroloquinoline alkaloids, yellow mycenaflavins A, B, and C, and the purple mycenaflavin 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 mycenaflavins A, B, and C. The purple mycenaflavin D is the first known dimeric pyrroloquinoline alkaloid with a C-C bridge between the two pyrroloquinoline units. Although the minor pyrroloquinoline alkaloid constituent mycenaflavin A exhibits only moderate bioactivity against the soil bacterium Azoarcus tolulyticus, the major pyrroloquinoline alkaloid constituent haematopodin B is similarly active as the antibiotic gentamicin.

Total Synthesis of Mycenarubin A, Sanguinolentaquinone and Mycenaflavin B and their Cytotoxic Activities

“…Mycenarubin A ( 2 ) did not display activity against Azospirillum brasilense, Azoarcus tolulyticus or Azovibrio restrictus (1 µmol). Mycenaflavin B ( 4b ) did not exhibit activity against Azospirillum brasilense and Azoarcus tolulyticus but revealed moderate activity against Azovibrio restrictus (inhibition zone: Ø = 0.8 cm, 1 µmol) …”

“…Other pyrroloquinoline alkaloids have been isolated from Mycena rosea [mycenarubin A ( 2 )], Mycena sanguinolenta [sanguinone A and B along with the indolo‐6,7‐quinone alkaloid sanguinolentaquinone ( 3 )] and Mycena pelianthina (pelianthinarubin A and B) . Recently, the previously unknown pyrroloquinoline alkaloids mycenaflavin A ( 4a ) and mycenaflavin B ( 4b ) were isolated from the fruiting bodies of Mycena haematopus (Figure ) …”

Formaldehyde as a Chemical Defence Agent of Fruiting Bodies of Mycena rosea and its Role in the Generation of the Alkaloid Mycenarubin C

“…Further tests with 2 and other bacteria, fungi, and the nematode Caenorhabditis elegans were negative (Tables S1 and S2). Because mycenarubin D, differing from 1 only by the presence of a C=NH unit instead of a C=O unit at position 7, displayed considerable bioactivity; the presence of a C=NH unit at position 7 seems to be an important prerequisite for bioactivity of this type of pyrroloquinoline alkaloid.…”

“…Pyrroloquinoline alkaloids were earlier considered to be typically “marine alkaloids”, because known representatives, such as the batzellines, damirones, discorhabdines, isobatzellines, and makaluvamines, were isolated from marine sources. However, meanwhile, a considerable number of different pyrroloquinoline alkaloids have been isolated from fruiting bodies of other Mycena species, for instance, from Mycena haematopus , Mycena sanguinolenta , and Mycena pelianthina . Regarding volatile constituents, hexanal and hexan‐2‐one have been reported to be present in fruiting bodies of M. rosea…”

Structure Elucidation and Spectroscopic Analysis of Chromophores Produced by Oxidative Psilocin Dimerization

“…Indigo, indirubin and isatin (an indoline) were observed in the confrontation zone of two mushroom species. [18] Modified and extended indole systems, as found in the iminoquinone mycenarubin D of the mushroom Mycena haematopus [19] or in the β‐carboline infractopicrin of Cortinarius infractus , [20] were recognized as active against soil bacteria and conferring a highly bitter taste on the producer which deters feeding predators, respectively. In contrast, the ecological advantage for 2 production in Psilocybe mushrooms remains obscure.…”