Additional analysis of chemical diversity of the red algal genus Laurencia (Rhodomelaceae) from Japan

SUMMARY The halogenated secondary metabolite constitution of four species of the red algal genus Laurencia (Rhodomelaceae) from southern Japan is reported. Laurencia composita Yamada from Tanegashima Island (Kagoshima Prefecture) bears five sesquiterpenoids (2,10-dibromo-3-chloro-α-chamigrene and 2,10-dibromo-3-chloro-9-hydroxy-α-chamigrene, in addition to pre-pacifenol epoxide, johnstonol and pacifenol, which are known in other populations of this species). Laurencia intricata Lamouroux from Chinzei (Saga Prefecture) and Oomura Bay (Nagasaki Prefecture) bear a C15 aceto-genin, okamurallene. Laurencia majuscula (Harvey) Lucas from Tanegashima Island produces three sesquiterpenoids, (Z)-10,15-dibromo-9-hydroxy-chamigra-1, 3(15),7(14)-triene, 10-bromo-7-hydroxylaurene and 10,11-dibromo-7-hydroxylaurene, corresponding to those of one of its chemical races. Laurencia venusta Yamada from Tanegashima Island produces two sesquiterpenoids, cupalaurenol and cyclolaurenol, which were known only from a sea hare, Aplysia dactylomela Rang. This strongly suggests that Aplysia consumes L. venusta and concentrates these halogenated compounds.