Abstract: Objective To explore protective effect of secoisolariciresinol diglucoside(SDG)on ischemia-reperfeusion injury in ovariectomized rats.Methods Three-week-old female healthy Sprague-Dawley(SD)rats were divided into 7 groups:sham group, ovariectomized group, ischemia-reperfusion group and different dose of SDG intervention groups(10, 20, 50, 100 mg/kg).Serum total cholesterol(TC), triglyceride(TG), high-density lipoprotein cholesterol(HDL), low-density lipoprotein cholesterol(LDL)content, superoxide dismutase(SOD), malondialdehyde(MDA) level and caspase-3 activity in myocardial tissue were detected with biochemical methods.Myocardial infarction area was measured with Even's blue and 2, 3, 5-tripheny-2H-tetrazolianm chloride staining method.Pathological changes of myocardial cells were observed with light microscope.Myocardial cell apoptosis was detected by TdT-mediated d-UTP-biotin nick end-labeling(TUNEL).Results Compared with ovariectomized group, serum HDL content of ischemia-reperfusion group decreased significantly(P<0.05);TC, TG and LDL increased significantly(P<0.05).Myocardial pathological damage aggravated and myocardial infarction area increased.Serum SOD, MDA contents reduced(P<0.05).Myocardial apoptosis index increased(P<0.05).Compared with ischemia-reperfusion group, serum HDL of 50 mg/kg SDG group(3.285±0.327 mmol/L)increased;TC(5.508±0.479 mmol/L), TG(0.535±0.129 mmol/L), and LDL(3.290±0.358 mmol/L)reduced(P<0.05 for all);myocardial infarction area reduced and pathological damage of myocardial tissue alleviated;serum levels of SOD(285.786±31.287 U/ml), MDA(2.483±0.391 nmol/mL)reduced(P<0.05) and myocardial apoptosis index(17.57±0.84)decreased significantly(P<0.05).All of the changes showed dose-effect relationships.Conclusion SDG has a protective effect on myocardial ischemia-reperfusion injury in ovariectomized rats in vivo, and the effect may be related to the improvement of myocardial tissue antioxidant capacity and the reduction of the myocardial cell apoptosis.