DPPH radical scavenging and nitric oxide inhibitory activities of the constituents from the wood of Taxus yunnanensis

The H2O, H2O/MeOH (1 : 1) and MeOH extracts of the wood of Taxus yunnanensis possessed significant DPPH radical scavenging and nitric oxide (NO) inhibitory activities. Chemical investigation of these extracts led us to isolation of nineteen compounds, i. e., five Lignans, two simple phenolics, and twelve taxane-type diterpenes. Isotaxiresinol and seco-isolariciresinol, two major Lignans of the wood, possessed potent DPPH radical scavenging activities with IC 50 values of 21.7 and 28.9 microM, respectively. Similarly, coniferyl aldehyde, taxusin, 10-deacetyltaxuyunnanine C, hongdoushan A, and 2alpha,5alpha,10beta-triacetoxy-14beta-[( S)-2-methylbutyryloxy]-4(20),11-taxadiene showed potent NO inhibitory activity with IC 50 values of 18.0, 22.1, 28.5, 15.0 and 26.4 microM, respectively, which were either equal or lower than the positive control NG-monomethyl- L-arginine ( L -NMMA) with an IC 50 value of 28.5 microM.