| Summary: | The Arctic-derived fungus <i>Eutypella</i> sp. D-1 can produce numerous secondary metabolites, and some compounds exhibit excellent biological activity. Seven pimarane-type diterpenes, including three new compounds eutypellenone F (<b>1</b>), libertellenone Y (<b>2</b>), and libertellenone Z (<b>3</b>), and four known compounds (<b>4</b>–<b>7</b>), were isolated from fermentation broth of <i>Eutypella</i> sp. D-1 by the OSMAC strategy of adding ethanol as a promoter in the culture medium. Compound <b>2</b> has a rare tetrahydrofuran-fused pimarane diterpene skeleton. The anti-inflammatory activity of all compounds was evaluated. Compounds <b>3</b>–<b>6</b> showed a significant inhibitory effect on cell NO release at 10 μmol/L by in vitro experiments, of which <b>3</b>–<b>5</b> had inhibitory rates over 60% on nitric oxide (NO) release. Subsequently, the anti-inflammatory activity of <b>3</b>–<b>5</b> was evaluated based on a zebrafish model, and the results showed that <b>3</b> had a significant inhibitory effect on inflammatory cells migration at 40 μmol/L, while <b>4</b> and <b>5</b> had a significant inhibitory effect at 20 μmol/L. Moreover, compounds <b>3</b>–<b>5</b> have the same conjugated double bond structure, which may be an important group for these compounds to exert anti-inflammatory activity.
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