Eutypellenoids A–C, New Pimarane Diterpenes from the Arctic Fungus Eutypella sp. D-1

Abstract

Three new pimarane diterpenes, eutypellenoids A⁻C (<b>1</b>⁻<b>3</b>), together with a known compound, eutypenoid C (<b>4</b>), were isolated from the culture extract of <i>Eutypella</i> sp. D-1 derived from the Arctic region. Compounds <b>1</b>⁻<b>3</b> possessed an uncommon tetrahydrofuran-fused pimarane diterpene skeleton. The structures of all compounds were determined by detailed spectroscopic analysis, electronic circular dichroism (ECD) analysis, as well as a comparison with the literature data. Antibacterial, antifungal, and cytotoxic activities of these compounds were evaluated. Compound <b>2</b> displayed antibacterial activity against <i>Staphylococcus aureus</i> and <i>Escherichia coli</i> with MIC values of 8 and 8 μg/mL, respectively. Additionally, compound <b>2</b> showed antifungal activity against <i>Candida</i><i>parapsilosis</i>, <i>Candida albicans</i>, <i>Candida glabrata</i>, and <i>Candida tropicalis</i> with MIC values of 8, 8, 16, and 32 μg/mL, respectively. Furthermore, compound <b>2</b> exhibited moderate cytotoxic activity against HCT-116 cell line with IC₅₀ value of 3.7 μM.