Inhibition of platelet-activating factor receptor binding by aporphine andphenanthrenoid alkaloids from Aromadendron elegans

Six aporphine and one phenanthrenoid alkaloids isolated from Aromadendron e legans Blume were investigated for their inhibitory effect on platelet-acti vating factor (PAF) binding to rabbit platelets using H-3-PAF as a ligand, Of the compounds tested, (-)-N-acetylanonaine. 1-(N-acetyl-N-methylamino)et hyl-3,4,6-trimethoxy-7-hydroxy-phenanthrene, and predicentrine showed stron g inhibition of PAF receptor binding, with IC50 values of 52.4, 38.6, and 2 9.8 muM, respectively. The flexibility of the biphenyl system of the aporph ine and the presence of methoxy groups at C-9 and C-10 were all preferable in binding to the receptor.