Ugandenial A, a New Drimane-type Sesquiterpenoid from Warburgia ugandensis

One new drimane-type sesquiterpenoid, named ugandenial A ( 1), was isolated from the ethyl acetate extract of the bark of Warburgia ugandensis (Canellaceae) together with eight known drimane-type sesquiterpenoids: 11 alpha-hydroxycinnamosmolide ( 2), warburganal ( 3), polygodial ( 4), mukaadial ( 5), dendocarbin A ( 6), 9 alpha-hydroxycinnamolide ( 7), dendocarbin L ( 8) and dendocarbin M ( 9). Their structures were established by detailed spectroscopic analysis. In addition a keto-enol equilibrium was demonstrated for compound 1 through a detailed NMR analysis run in CD2Cl2 at 190 K. Cytotoxicity of the isolated compounds against KB cells was evaluated.