Brominated Sesquiterpenes from the Red Alga Laurencia obtusa

Abstract

Four new sesquiterpenes, (8R*)-8-bromo-10-epi-β-snyderol (1), (8S*)-8-bromo-β-snyderol (2), 5-bromo-3-(3‘-hydroxy-3‘-methylpent-4‘-enylidene)-2,4,4-trimethylcyclohexanone (3), and the epoxide 4, have been isolated from the chloroform−methanol extract of Laurencia obtusa, together with the three known compounds α-snyderol (5), α-snyderol acetate (6), and stigmasterol. The structures of the isolated compounds were elucidated through spectroscopic analyses. Compound 1 showed antimalarial activity, with IC₅₀ values of 2700 and 4000 ng/mL against the D6 and W2 clones of Plasmodium falciparum, respectively.