Sesquiterpenoids of Laurencia majuscula (Ceramiales, Rhodophyta) from the Ryukyu Islands, Japan

SUMMARY Two populations of the red alga Laurencia majuscula (Harvey) Lucas (Rhodomelaceae, Ceramiales) from Taketomi Island and Hateruma Island, the Ryukyu Islands, Japan, have been characterized on the basis of both morphological features and halogenated secondary metabolite content. These populations have smaller and more slender thalli than those of other regions. Furthermore, the populations contain two chamigrane‐type Sesquiterpenoids, (2 R , 3 R , 5 S )‐5‐acetoxy‐2‐bromo‐3‐chlorochamigra‐7(14),9‐dien‐8‐one and (2 R , 3 R )‐2‐bromo‐3‐chlorochamigra‐7(14), 9‐dien‐8‐one, and a laurane‐type sesquiterpenoid, debromoisolaurinterol, as secondary metabolites which are different from those previously reported from other populations. These results are consistent with the concept of ‘chemical races’ within a single species of Laurencia.