Seven
new 4-hydroxy-6-phenyl-2H-pyran-2-one (HPPO)
derived meroterpenoids, 1-methyl-12a,12b-epoxyarisugacin M (1), 1-methyl-4a,12b-epoxyarisugacin M (2), 2,3-dihydroxy-3,4a-epoxy-12a-dehydroxyisoterreulactone
A (3), 2-hydroxy-12a-dehydroxyisoterreulactone A (4), 3′-demethoxyterritrems B′ (5), 4a-hydroxyarisugacin P (6), and 1-epi-arisugacin
H (7), together with two known analogues (8 and 9), were isolated from the marine-derived fungal
strain Penicillium sp. SCSIO 41691. Their structures
were elucidated by spectroscopic methods, and the absolute configurations
of compounds 1 and 3 were determined by
single-crystal X-ray diffraction. Among them, 1 and 2 had a unique methyl migration in the basic meroterpenoid
skeleton with a 12a,12b-epoxy or 4a,12b-epoxy group, and 3 was a highly oxygenated HPPO-derived meroterpenoid featuring a rare
6/5/6/6/6/6 hexacyclic system with a 3,4a-epoxy group. Biologically, 5 exhibited inhibitory activity against lipopolysaccharide-induced
nitric oxide production in RAW 264.7 cells with an IC50 value of 21 μM, more potent than the positive control indomethacin.