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

Abstract

Mycenarubin C, a previously unknown red pyrroloquinoline alkaloid, was isolated from fruiting bodies of the mushroom Mycena rosea and its structure was elucidated mainly by NMR spectroscopy and mass spectrometry. Unlike mycenarubin A, the major pyrroloquinoline alkaloid in fruiting bodies of M. rosea, mycenarubin C, contains an eight‐membered ring with an additional C1 unit that is hitherto unprecedented for pyrroloquinoline alkaloids known in nature. Incubation of mycenarubin A with an excess of formaldehyde revealed that mycenarubin C was generated nearly quantitatively from mycenarubin A. An investigation into the formaldehyde content of fresh fruiting bodies of M. rosea showed the presence of considerable amounts of formaldehyde, with values of 5 μg per gram of fresh weight in fresh fruiting bodies. Although mycenarubin C did not show bioactivity against selected bacteria and fungi, formaldehyde inhibits the growth of the mycoparasite Spinellus fusiger at concentrations present in fruiting bodies of M. rosea. Therefore, formaldehyde might play an ecological role in the chemical defence of M. rosea against S. fusiger. In turn, S. fusiger produces gallic acid—presumably to detoxify formaldehyde by reaction of this aldehyde with amino acids and gallic acid to Mannich adducts.

Co-cultivation of Mortierellaceae with Pseudomonas helmanticensis affects both their growth and volatilome

“…produces higher amounts of ethanol to inhibit Guignardia citricarpa, a phytopathogen causing black spot in citrus 38 . Formaldehyde produced in the fruiting bodies of Mycena rosea represents an efficient defence mechanism against the fungal mycoparasite Spinellus fusiger 39 . Pseudomonas helmanticensis produced VOC ms31.0182, tentatively annotated as formaldehyde, in high concentrations (91 ppbV) (Fig.…”

Tricrilactones A–H, Potent Antiosteoporosis Macrolides with Distinctive Ring Skeletons fromTrichocladium crispatum, an Alpine Moss‐Associated Fungus

“…However, no [Me‐ d 3 ]‐methionine could be introduced into any of the compounds 2 – 4 . Given that some fungi are capable of producing formaldehyde through direct oxidation of sarcosine or methanol, [24] we conducted the isotope‐labeling experiment using [D 4 ]‐methanol. To our surprise, the deuterated compounds 2 – 4 were generated with the corresponding [M+H] + ions at m / z 411 ( 2 and 3 ; Figures S27 and S28) and 407 ( 4 ; Figure S29), respectively, showing a 2 Da increment from that of 2 – 4 without exposure to [D 4 ]‐methanol.…”

“…A methylene‐bridged dimer was obtained (see the Supporting Information), suggesting that the coupling between protrilactione A and formaldehyde could occur without an enzyme during the biosynthesis of 2 – 4 in the fungal cells. Formaldehyde is well‐known for its toxicity against various fungi; [24] hence, the formaldehyde‐triggered dimerization reactions could be a new strategy for self‐detoxification of fungi that needs further investigation. To the best of our knowledge, this is the first report of formaldehyde‐induced macrolide dimers from nature.…”

Structures and Biological Activities of Alkaloids Produced by Mushrooms, a Fungal Subgroup

“…Successively, mycenarrubin C ( 34 , Figure 3 ) was isolated from M. rosea [ 37 ]. Compound 34 is a special pyrroloquinoline alkaloid with an eight-membered ring, which contains an additional C 1 unit.…”

“…Mycenarubin D (31) showed an antibacterial activity against Azovibrio restrictus, Azoarcus tolulyticus, and Azospirillum brasilense, whereas mycenarubin A (29) was shown to be inactive as an antibacterial compound [34,37]. Thus, the presence of the C=NH unit at position 7 is a key group for the bioactivity of these pyrroloquinoline alkaloids.…”