Four new phenylethanoid and flavonoid glycoside dimers from the fruits of Forsythia suspensa and their neuroprotective activities

Abstract

During our continuing study on the fruits of Forsythia suspensa, one new heterodimer (forsythoneoside E) containing a flavonoid and a phenethanoid glycoside formed through a pyran ring, one new phenylethanoid glycoside dimer (forsythoneoside F) with a C–O bond, along with a pair of flavonoid glycoside dimers (forsythobiflavone A and B) possessing different axial chirality, were obtained. Their chemical structures, including absolute configurations, were established by NMR, HRESIMS, UV, IR, and ECD spectroscopic data and comparison of experimental and calculated electronic circular dichroism (ECD) spectra. All of the compounds were evaluated for their neuroprotective effects against rotenone-induced neurotoxicity in PC12 cells at 1 μM.