Andrastin-type meroterpenoids, α-pyrone polyketides, and sesquicarane derivatives from Penicillium sp., a fungus isolated from Pinus koraiensis seed

The genus Penicillium has provided us with the household antibiotic penicillin and the well-known lipid-lowering agent mevastatin. The strain Penicillium sp. SZ-1 was found to grow vigorously in an intact Pinus koraiensis seed, it is inferred that the strain may develop unique mechanisms associated with the biosynthesis of rare metabolites. Further fermentation of the strain on solid rice medium yielded thirteen undescribed compounds, including three andrastin-type meroterpenoids (1-3), two α-pyrone polyketides (4 and 5), and eight sesquicarane derivatives (6-13), along with seven known compounds (14-20). Their structures were determined by detailed analysis of the spectroscopic and spectrometric data (NMR and HRESIMS), in addition to comparisons of the experimental and calculated ECD data for absolute configurational assignments. The hemiacetal moiety in compounds 1 and 2 and the 3α-hydroxy group in compound 3 were rarely found in the andrastin-type meroterpenoid family. The sesquicaranes belong to a small group of sesquiterpenoid that are rarely reported. Bioassay study showed that compound 1 exhibited inhibitory effects against Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922 with MIC values of 64 and 32 μg/mL, respectively. In addition, compounds 1 and 3 displayed weak DPPH radical scavenging activities. The andrastins and sesquicaranes in this study enriched the structural diversity of these classes of terpenoids. Of note, this study is the first report on the metabolites of a fungus isolated from P. koraiensis seed.