Antioxidant effects of diarylheptanoid derivatives from Alnus japonica on human LDL oxidation

Two diarylheptanoids, oregonin (1) and hirsutanone (2), were isolated by bioassay-guided fractionation of the methanol extracts of the leaves of Alnus japonica Steud and their structures were elucidated from their spectroscopic data. Compounds 1 and 2 exhibited significant low-density lipoprotein (LDL)-antioxidant activities, e. g., thiobarbituric acid-reactive substances (TBARS) assay (1: IC50 = 3.2 microM, 2: IC50 = 1.5 microM), lag time (1 : 162 min, 2 : 230 min at 2.0 microM, control: 63 min), relative electrophoretic mobility (REM, inhibition of 1 : 71%, 2 : 75% at 10 microM), apoB-100 fragmentation (inhibition of 1 : 27.3%, 2 : 40.3% at 10 microM) and macrophage-mediated LDL oxidation (inhibition of 1 : 82%, 2 : 84% at 1 microM).