The novel natural products joannesialactone, (-)-a-barbatenal, 4-hydroxy-10-epirotundone, and the E- and Z-isomers of 2-(4-hydroxyphenyl)ethenyl-ct-L-rhamnopyranoside and the 3-O-rhamnosides of the dimeric proanthocyanidins afzelechin-(4a ~ 8)-epiafzelechin-3-O-vanillate, afzelechin-(4a ~ 8)-epicatechin-3- O-vanillate, afzelechin-(4~t ~ 8)-epiafzelechin-3-O-syringate and afzelechin-(4ct ~ 8)-epicatechin-3-O-syringate have been isolated from the root bark of Joannesia princeps, along with the antibiotic principle cyperenal, the colouring matter assufulvenal, curcusones C and D and 16 further known compounds. Structure determination was achieved mainly by spectroscopic studies and/or by comparison with authentic substances.