A new polybrominated indole, 4,5,6-tribromo-2-methylsulfinylindole (1), and eleven known metabolites 2–12 were isolated from the acetone extract of the red alga Laurencia brongniartii. Structure of the new compound 1 was elucidated by 1D and 2D NMR experiments. Cytotoxic, anti-inflammatory, and antibacterial activities of these sulfur-containing polybromoindoles were evaluated.

Chemical investigation of the red alga Laurencia tristicha led to the discovery of eight new halogenated chamigrane-type sesquiterpenoids (1-8) and one new bromocuparane-type sesquiterpene (9), along with nine known related metabolites (10-18). Their structures were elucidated on the basis of extensive spectroscopic analyses, and the absolute configurations of 1-8 were proposed by comparison to the biosynthetically related known compound 12. Cytotoxicity, antibacterial, and anti-inflammatory activities of these isolates were also investigated. The results showed that compound 11 exhibited good antibacterial activity against Serratia marcescens compared to the positive control ampicillin at a dosage of 100 μg/disk. Compound 17 showed strong inhibition toward elastase release generation at 10 μM.