Highly modified steroids from Inonotus obliquus

Abstract

Six undescribed steroids were isolated from the fungus Inonotus obliquus. Notably, compounds 1 and 2 represented the first example of 8,14-seco-4-methylpregnane. By spectroscopic data analyses, quantum chemical calculations and DP4+ probability analysis, their structures were unambiguously determined. The absolute configurations of the compounds 1-6 were defined by comparison of their experimental and calculated electronic circular dichroism (ECD) spectra data. The structure of compound 1 was also confirmed by single-crystal X-ray diffraction. All isolated steroids were evaluated for their neuroprotective activities against H2O2-induced cell injury in human neuroblastoma SH-SY5Y cells, among which compound 2 showed moderate activity at 12.5 μM.