New lignans from the roots of Schisandra sphenanthera.

Nine new lignans (1-8, 13) and five known ones (9-12, 14) have been isolated from the roots of Schisandra sphenanthera and were tested for their capacity to scavenge 2,2-diphenyl-1-Picryl-hydrazyl (DPPH). Of these lignans tested, compounds 1, 7, 8 and 13 exhibited noteworthy antioxidant activity with IC50 values of 92, 115, 35 and 48 μg/mL, respectively. The anti-oxidative haemolysis of human red blood cells (RBCs) activity of the most active compound 8, which is similar to that of vitamin C, was evaluated.