Pestalustaines A and B, unprecedented sesquiterpene and coumarin derivatives from endophytic fungus Pestalotiopsis adusta

Abstract Pestalustaines A ( 1 ) and B ( 2 ), one unique sesquiterpene possessing an unusual 5/6/7-fused tricyclic ring system and one unprecedented coumarin derivative bearing 6/6/5/5-fused tetracyclic ring system, were isolated from the plant-derived Pestalotiopsis adusta . Their structures with absolute configurations were established by extensive NMR analysis, X-ray crystallography, and CD spectra associated with TD-DFT calculation. Hypothetical biosynthetic pathways for compounds 1 and 2 are proposed. Compounds 1 and 2 showed weak to moderate cytotoxic activities against three human tumor cell lines HeLa, HCT116, and A549, whose IC 50 values were ranged from 21.01 to 55.43 μM.