Halogenated Sesquiterpenoids from the Red Alga Laurencia tristicha Collected in Taiwan

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.