Twelve new polyketides, including
a naphthoquinone derivative,
penithoketone (1), and 11 chromone derivatives, penithochromones
A–L (2–12), together with
three known compounds (13–15) were
isolated from the deep-sea-derived fungus Penicillium thomii YPGA3. The structures of the metabolites were elucidated based on
extensive analyses of the spectroscopic data, and the configuration
of 1 was resolved by quantum chemical calculations of
NMR shifts and ECD spectra and comparisons to experimental data. Compound 1, containing a naphthoquinone-derived moiety substituted
with a butenolide unit, represents a new modified naphthoquinone skeleton.
Interestingly, the 5,7-dioxygenated chromone derivatives 2–13 possessed different alkyl acid or alkyl ester
side chain lengths, and those with side chain lengths of seven carbon
atoms were discovered from nature for the first time. The metabolites
were evaluated for their cytotoxicity against four cancer cell lines;
compounds 1 and 15 were found to be active,
with IC50 values ranging from 4.9 to 9.1 μM.