Investigation of Insect Repellent Activity of Cyclocolorenone Obtained from the Red Alga Laurencia intricata

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 mu 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.