Spiroketals, isocoumarin, and indoleformic acid derivatives from saline soil derived fungus Penicillium raistrickii

Six new compounds, named peneciraistins A–F (1–6), were isolated from saline soil derived fungus Penicillium raistrickii. Among them, compounds 1 and 2 are rare benzannulate 6,6-spitoketals, and compounds 5 and 6 are the first naturally occurring 3-indoleformic acid derivatives. Their structures were elucidated by means of their detailed NMR and MS spectroscopic data. Their absolute configurations were assigned by the modified Mosher method, CD excitation chirality method or optical rotation by comparison with those of known compounds. Their cytotoxicities were also reported against A549 and MCF-7 cell lines along with radical scavenging activities against DPPH (1,1-diphenyl-2-picrylhydrazyl).