A new indole alkaloid, 11,12-dimethoxyhenningsamine, was isolated from the roots of Strychnos cathayensis, together with 19 known compounds. The structure of this new compound was determined through spectroscopic and mass-spectrometric analyses. Among the isolated compounds, 11-methoxyhenningsamine and aesculetin dimethyl ether exhibited potent inhibition (IC(50) < 5.5 microg/ml) on superoxide-anion generation and elastase release by human neutrophils in response to fMet-Leu-Phe/cytochalasin B.