a b s t r a c tFour species of marine benthic algae (Laurencia filiformis, L. intricata, Gracilaria domingensis and G. birdiae) that belong to the phylum Rhodophyta were collected in Espírito Santo State, Brazil and investigated concerning their biochemical composition (fatty acid, total lipid, soluble proteins, amino acid and ash). The total content of lipid (% dry weight) ranged from 1.1% to 6.2%; fatty acid from 0.7% to 1.0%; soluble protein from 4.6% to 18.3%, amino acid from 6.7% to 11.3% and ash from 22.5% to 38.4%. Judging from their composition, the four species of algae appear to be potential sources of dietary proteins, amino acids, lipids and essential fatty acids for humans and animals.

Eleven sesquiterpenes (1-11) and one long chain aldehyde (12) have been isolated from the dichloromethane extract of the red alga Laurencia scoparia. Four of them are new natural products. Scopariol (1) is a new natural product with an unusual rearranged chamigrane-type structure. The other three are beta-chamigrenes: isorigidol (2), (+)-3-(Z)-bromomethylidene-10 beta-bromo-beta-chamigrene (3), and (-)-3-(E)-bromomethylidene-10 beta-bromo-beta-chamigrene (4). The in vitro activity of compounds 1-12 against the parasitant stage of Nippostrongylus brasiliensis (L4) has been studied.

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Three novel halogenated beta-bisabolene sesquiterpenoids (1-3), together with two know triquinane alcohol sesquiterpenes (6 and 7), were isolated from the red alga Laurencia scoparia and their structures elucidated by spectroscopic methods. Single-crystal X-ray crystallography allowed us to confirm the structure of 1 as well as to determine the absolute configuration of all stereocenters. To the best of our knowledge, the isolation of beta-bisabolenes from the genus Laurencia has no precedent in the literature. Compound 1 showed weak in vitro anthelmintic activity against parasitant stage (L4) Nippostrongilus brasiliensis.