Chemical Compositions of the Marine Red Alga Laurencia composita Collected in Japan

Marine red alga Laurencia composita was collected from seven sampling locations in Japan, and all samples were identified based on morphological studies as well as rbcL sequencing analysis. This is the first report of the isolation of (-)-8-bromo-9-hydroxy-(E)-γ-bisabolene (1) as a natural product, and bisabolene-type and β-chamigrene-type sesquiterpenes found in L. composita collected in Japan. In previous Japanese reports of L. composita, highly oxidized α-chamigrene-type sesquiterpenes were isolated as their major secondary metabolites. Therefore, these populations are the fissure chemical race in L. composita. All isolated compounds were tested for their insect-repellent activity against the adult maize weevil Sitophilus zeamais.