The Khamkhains, Neurotrophic Drimane-Type Sesquiterpenoids Derived from a Polyporaceous Basidiomycete Originating from Thailand

Eight unprecedented terpenoids
were isolated from submerged cultures
of a polyporoid basidiomycete originating from Thailand (which had
been referred to as “Cerrena sp.” in
a previous publication) by preparative chromatography. Their chemical
structures were elucidated by extensive two-dimensional nuclear magnetic
resonance (NMR) spectroscopy and high-resolution mass spectrometry.
One of the compounds was crystallized, and its absolute configuration
was established by X-ray crystallography. Among the isolated metabolites
were several members of the rare nitrogen-containing drimane type
and one dimeric drimane, which consists of a nitrogen-containing monomer
and a regular monomer. The latter compound represents a hitherto unknown
type of terpenoid natural product. The metabolites were subjected
to a biological characterization, and some of them showed significant
neurotrophic effects. Notably, several of the compounds significantly
enhanced the outgrowth of neurites in PC12 cells when treated with
5 ng/mL nerve growth factor. On the other hand, they were devoid of
significant cytotoxic and antimicrobial effects.