Antioxidant activities of a new lignan and a neolignan from Saururus chinensis

A new diarylbutane lignan, 2′-hydroxy dihydroguaiaretic acid (4), and a known 8-O-4′-type neolignan, machilin D (5), were isolated from the ethyl acetate extracts of the underground parts of Saururus chinensis. Compounds 4 and 5 exhibited low-density lipoprotein (LDL)-antioxidant activity in the thiobarbituric acid-reactive substances (TBARS) assay (4: IC50 = 3.3 μM and 5: IC50 = 3.8 μM), the lag time of conjugated diene production, the relative electrophoretic mobility (REM) of ox-LDL, the apoB-100 fragmentation on copper-mediated LDL oxidation and the macrophage-mediated LDL oxidation, and radical DPPH scavenging activity.