Eutypellacytosporins A–D, Meroterpenoids from the Arctic Fungus <i>Eutypella</i> sp. D-1

Abstract

The Arctic fungus <i>Eutypella</i> sp. D-1, previously found to produce a variety of cytotoxic cyclopropyl-fused and cyclobutyl-fused pimarane diterpenoids when grown in the defined medium, was induced to produce unusual metabolites by growing on solid rice medium. A chemical investigation on the rice medium extract led to the isolation of four new meroterpenoids, eutypellacytosporins A-D (<b>1</b>-<b>4</b>), along with the known biogenetically related compound cytosporin D (<b>5</b>). The structures of the new compounds were elucidated by their detailed spectroscopic analysis and modified Mosher's method. Compounds <b>1</b>-<b>4</b> may be formed by the 12,32-ester linkage of two moieties, cytosporin D (<b>5</b>) and decipienolide A or B. All isolated compounds, except <b>5</b>, showed weak cytotoxicity against DU145, SW1990, Huh7, and PANC-1 cell lines with IC₅₀ values ranging from 4.9 to 17.1 μM.