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 fungusAspergillusversicolorA18 has led to the isolation of 11 homo/hetero-dimers of aromatic bisabolane sesquiterpenoids including eight diphenyl ether-coupled aromatic bisabolanes (1a/1band5–10) and three homodimers (2–4), together with their monomers including three aromatic bisabolanes (11–13) and two diphenyl ethers (14and15). 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 enantiomers1aand1brepresent 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, and8–10) showed remarkable neuroprotective activities at 10 μM, being more active than the positive control edaravone.Keywords:diphenyl ether-coupled aromatic bisabolane;aromatic bisabolane dimer;marine-derived fungus;Aspergillus versicolor;neuroprotective activity