Homo/Hetero-Dimers of Aromatic Bisabolane Sesquiterpenoids with Neuroprotective Activity from the Fungus Aspergillus   versicolor A18 from South China Sea.

Chromatographic fractionation of the EtOH extracts of the marine-derived fungus Aspergillus   versicolor A18 has led to the isolation of 11 homo/hetero-dimers of aromatic bisabolane sesquiterpenoids including eight diphenyl ether-coupled aromatic bisabolanes ( 1a / 1b and 5 - 10 ) and three homodimers ( 2 - 4 ), together with their monomers including three aromatic bisabolanes ( 11 - 13 ) and two diphenyl ethers ( 14 and 15 ). Their structures and absolute configurations were elucidated by extensive spectroscopic analysis including HRESIMS, 1D/2D NMR, calculated ECD, and the optical rotatory data. Among the four new compounds, (+/-)-asperbisabol A ( 1a / 1b ), asperbisabol B ( 2 ), and asperbisabol C ( 3 ), the enantiomers 1a and 1b represent an unprecedented skeleton of diphenyl ether-coupled aromatic bisabolane sesquiterpenoids with a spiroketal core moiety. The neuroprotective effects of selected compounds against sodium nitroprusside (SNP)-induced injury were evaluated in PC12 cells by the MTT assay. Five compounds ( 1a , 6 , and 8 - 10 ) showed remarkable neuroprotective activities at 10 μM, being more active than the positive control edaravone.