Protective Effects of Chemical Constituents from the Roots of Polygala sibirica L. on PC12 Cells Damage Induced by H2O2

To elucidate the major bioactive chemical constituents of Polygala sibirica L. affording the treatment of Alzheimer's disease, phytochemical investigation on the roots of the plant have resulted in the isolation of 11 compounds. Their structures were identified as tenuifolin (1), polygalasaponin XXVIII (2), arilloside B (3), zigu-glucoside II (4), zigu-glucoside I (5), sibiricose A(1) (6), sibiricose A(3) (7), tenuifoliside B (8), 7-hydroxy-1,2,3-trimethoxyxanthone (9), 6-hydroxy-1,2,3,7-tetramethoxyxanthone (10) and beta-sitosterol (11) by the analysis of spectroscopic data. Protective effects of 11 compounds on damaged PC12 cells were evaluated in vitro. The results indicated that compounds 1-5 could significantly protect PC12 cells away from the damage induced by H2O2 in vitro via proliferating PC12 cells, reducing the content of MDA, decreasing activity of LDH, and increasing the activity of SOD.