Three known secondary metabolites were isolated from the organic extract of Laurencia intricata. Their structures were identified by NMR and MS experiments and comparison with the literature data. An aromadendrane sesquiterpene, (+)-cyclocolorenone showed strong repellent activity against the maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) adults. It had the same activity as natural insecticides, pyrethrins, with a ED50 value of 2.0 g/cm 2 . This is the first report of insect repellent activity of (+)cyclocolorenone. The results suggest that the red alga Laurencia is a promising source of bioactive compounds which can be used as potential biocontrol agents for stored-product insects.

We examined the chemical constitution of the red alga Laurencia saitoi Perestenko, collected from Katsuura, Boso Peninsula, Chiba Prefecture, Japan. This specimen produced a new polyhalogenated acetogenin, named katsuurallene (1), which structure was determined by the spectral methods, along with known diterpene, deoxyparguerol (2) and triterpene, thyrsiferol (3). In this paper we describe the structural elucidation of katsuurallene together with some biological activities.

We report on the chemical characteristics of the red alga Laurencia japonensis, collected off the coast of Yoshio, Katsuura, Boso Peninsula, Japan. We isolated two new brominated C 15 -acetogenins in this species, which we name katsuurenyne A (1) and katsuurenyne B (2), along with two already known halogenated terpenes [2,10-dibromo-3-chloro--chamigrene (7) and aplysiadiol (8)]. We extensively analysed spectral data (from IR, ESI-MS, 1D-NMR and 2D-NMR) to confirm the structure of these compounds.