Structure elucidation and NMR assignments for two xanthone derivatives from a mangrove endophytic fungus (No. ZH19)

Abstract

The structure elucidations and complete (1)H and (13)C NMR assignments are reported for two new xanthone derivatives: 1,7-dihydroxy-2-methoxy-3-(3-methylbut-2-enyl)-9H-xanthen-9-one (1) and 1-hydroxy-4,7-dimethoxy-6-(3-oxobutyl)-9H-xanthen-9-one (2). Both of these secondary metabolites were isolated from the fermentation medium of a mangrove endophytic fungus (No. ZH19). High-resolution electron impact mass spectrometry (HREIMS), Fourier transform infrared (FT-IR) absorption spectrometry, and NMR experiments including gCOSY, gHMQC, and gHMBC were used for the determination of the structures and NMR spectral assignments. Preliminary pharmacological test showed that compounds (1) and (2) inhibited KB cells with IC(50) values of 20 and 35 micromol/ml, and KB(V)200 cells with IC(50) values of 30 and 41 micromol/ml, respectively.