SECONDARY METABOLITE CHEMISTRY OF THE AUSTRALIAN BROWN ALGA ENCYOTHALIA-CLIFTONII - EVIDENCE FOR HERBIVORE CHEMICAL DEFENSE

Two bis-prenylated phenols have been isolated from the Western Austral ian brown alga Encyothalia cliftonii Harvey. The structures of these c ompounds were determined by spectral and chemical methods. The major m etabolite, 2,4-bis(3-methylbut-2-enyl)phenol, previously isolated as a minor metabolite from the related alga Perithalia caudata, showed sig nificant feeding deterrence toward the herbivorous sea urchin Tripneus tes esculentus (Leske). The minor metabolite is a new compound in whic h hydration of one of the isopentenyl olefinic bonds has taken place.