Furanoaustinol and 7-acetoxydehydroaustinol: new meroterpenoids from a marine-derived fungal strain Penicillium sp. SF-5497

Two new meroterpenoid-type fungal metabolites, furanoaustinol (1) and 7-acetoxydehydroaustinol (2), were isolated from the ethyl acetate extract of a marine-derived fungal strain Penicillium sp. SF-5497, along with eight (3–10) known meroterpenoids. Their structures were elucidated mainly based on the analysis of their NMR (1D and 2D) and MS data. Particularly, the novel meroterpenoid, furanoaustinol (1), belonging to the austin group, was identified to possess an unprecedented hexacyclic ring system. Biological evaluation of these compounds revealed that furanoaustinol (1) weakly inhibited the activity of protein tyrosine phosphatase 1B in a dose-dependent manner with an IC50 value of 77.2 μM. In addition, 7-acetoxydehydroaustinol (2) and four other known meroterpenoids (5, 7, 9, and 10) weakly suppressed the overproduction of nitric oxide in lipopolysaccharide-challenged BV2 microglial cells with IC50 values of 61.0, 30.1, 58.3, 37.6, and 40.2 μM, respectively.