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

Two new octaketides, cytosporones W () and X (), along with eight known cytosporone derivatives [(±)-], were isolated from mangrove endophytic fungus sp. ZJHJYZ-1. Compounds and 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 and . In bioassays, (±)- exhibited promising inhibitory activities against , , and with MIC, respectively, for 12.5, 12.5, and 3.13 μM.