Abstract
Bioassay-guided high-performance liquid chromatography analysis of a MeOH extract of Iris clarkei seeds yielded the resveratrol-type oligomeric stilbenes, ampelopsin B and alpha-viniferin, which antagonize the action of 20-hydroxyecdysone; with a 20-hydroxyecdysone concentration of 50 nM, the ED50 values were 33 microM and 10 microM, respectively. The structures of these compounds were determined by spectroscopic analysis, notably ultraviolet, liquid secondary ion mass spectrometry and modern one- and two-dimensional nuclear magnetic resonance techniques.