New Carboxamides and a New Polyketide from the Sponge-Derived Fungus Arthrinium sp. SCSIO 41421.

New carboxamides, (±)-vochysiamide C ( 1 ) and (+)-vochysiamide B ( 2 ), and a new polyketide, 4 S ,3a S ,9a R -3a,9a-deoxy-3a hydroxy-1-dehydroxyarthrinone ( 3 ), were isolated and identified from the sponge-derived fungus Arthrinium sp. SCSIO 41421, together with other fifteen known natural products ( 4 - 18 ). Their structures including absolute configurations were determined by detailed NMR, MS spectroscopic analyses, calculated electronic circular dichroism (ECD), as well as quantum-chemical NMR calculations. Preliminary bioactivity screening and molecular docking analysis revealed that several natural products exhibited obvious enzyme inhibitory activities against acetylcholinesterase (AChE), such as 2,3,6,8-tetrahydroxy-1-methylxanthone ( 4 ) with an inhibitory rate 86% at 50 μg/mL.