Antioxidative Diarylheptanoids from the Fruits of Alpinia oxyphylla

The antioxidative activity of Alpinia oxyphylla was investigated through measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and inhibitory activity for linoleic acid peroxidation. Two antioxidative diarylheptanoids, yakuchinone A (1) and oxyphyllacinol (2), were isolated from the fruits of A. oxyphylla using thin layer chromatography (TLC) autographic assays. The DPPH scavenging activities of the compounds (IC 50 =1, 57±2.1 μM; 2, 89±3.1 μM) were lower than vitamin C (IC 50 =51±1.1 μM), but higher than butylated hydroxytoluene (BHT, IC 50 =99±2.2 μM). Also, inhibitory activities for linoleic acid peroxidation of the compounds (IC 50 =1, 0.19±0.011 mM; 2, 0.31±0.009 mM) were higher than those of vitamin C (IC 50 =0.59±0.017 mM) and BHT (IC 50 =0.52±0.014 mM). In addition the 13C-NMR data of oxyphyllacinol (2) have been first reported in this paper.