Three quinolizidine dimers from the seeds of Sophora alopecuroides and their hepatoprotective activities

Sophoralines A–C,three novel[2+2]cycloaddition dimers of matrine-based alkaloids with an unprecedented 6/6/6/6/4/6/6/6/6 nonacyclic skeleton containing 11 stereogenic centers,were isolated from Sophora alopecuroides.Their structures were determined by spectroscopic methods,and the absolute configurations were further determined by single-crystal X-ray diffraction analysis for 1 and quantum chemical calculations of electronic circular dichroism(ECD)spectra for 2 and 3.Moreover,1 exhibited excellent hepatoprotective activities in acetaminophen-induced liver injury in vitro and in vivo.