Halogenated Sesquiterpenoids from the Red Alga Laurencia tristichaCollected in Taiwan

Chemical investigation of the red alga Laurencia tristichaled 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 1–8were 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 11exhibited good antibacterial activity against Serratia marcescenscompared to the positive control ampicillin at a dosage of 100 μg/disk. Compound 17showed strong inhibition toward elastase release generation at 10 μM.