Diterpenoid feeding-deterrents from Laurencia saitoi

Abstract Three new diterpenes and 14 known, brominated and non-brominated diterpenes have been isolated from the red alga Laurencia saitoi collected in ‘Isoyake areas’ in the Sea of Japan. Some of these diterpenes showed significant feeding-deterrent activity against young abalone ( Haliotis discus hannai ) and young sea urchins ( Strongylocentrotus nudus and S. intermedius ), thus suggesting that these metabolites provide a chemical defense against marine herbivorous animals in ‘Isoyake areas’.