Cytosporones W and X: Two Mutually Converting Epimers from a Mangrove Endophytic Fungus <i>Diaporthe</i> sp. ZJHJYZ-1

Abstract

Two new octaketides, cytosporones W (<b>1</b>) and X (<b>2</b>), along with eight known cytosporone derivatives [(±)-<b>3-9</b>], were isolated from mangrove endophytic fungus <i>Diaporthe</i> sp. ZJHJYZ-1. Compounds <b>1</b> and <b>2</b> were a pair of epimers, whose configuration of C-1 could mutually convert, causing racemization of the lactone ring. The planar structures of compounds were elucidated through detailed 1D, 2D NMR, and HR-ESI-MS analysis. ECD spectra comparison and modified Mosher ester method were applied to determine the absolute configuration of <b>1</b> and <b>2</b>. In bioassays, (±)-<b>3</b> exhibited promising inhibitory activities against <i>Bacillus subtilis</i>, <i>Pseudomonas aeruginosa</i>, and <i>Penicillium italicum</i> with MIC, respectively, for 12.5, 12.5, and 3.13 μM.