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

Two new octaketides, cytosporones W ( 1 ) and X ( 2 ), along with eight known cytosporone derivatives [(±)- 3-9 ], were isolated from mangrove endophytic fungus Diaporthe sp. ZJHJYZ-1. Compounds 1 and 2 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 1 and 2 . In bioassays, (±)- 3 exhibited promising inhibitory activities against Bacillus subtilis , Pseudomonas aeruginosa , and Penicillium italicum with MIC, respectively, for 12.5, 12.5, and 3.13 μM.