NEW LEUKOTRIENE-B4 RECEPTOR ANTAGONIST - LEUCETTAMINE-A AND RELATED IMIDAZOLE ALKALOIDS FROM THE MARINE SPONGE LEUCETTA-MICRORAPHIS

Three new imidazole alkaloids, leucettamines A [l] and B [2] and leucettamidine [3], have been isolated from the Palauan sponge Leucetta microraphis. Their structures were established on the basis of extensive spectral analyses. Leucettamine A showed potent leukotriene B, receptor binding activity (K(i) = 1.3 muM), while leucettamine B was essentially inactive (K(i) = 100 muM) and leucettamidine showed significant activity (K(i) = 5.3 muM). With leucettamine A identified as a pure LTB4 receptor antagonist, a new structure lead is presented to inflammation therapy.