Costatone C—A New Halogenated Monoterpene from the New Zealand Red Alga Plocamium angustum

摘要

Red algae of the genus Plocamium have been a rich source of halogenated monoterpenes. Herein, a new cyclic monoterpene, costatone C ( 7 ), was isolated from the extract of P. angustum collected in New Zealand, along with the previously reported (1 E ,5 Z )-1,6-dichloro-2-methylhepta-1,5-dien-3-ol ( 8 ). Elucidation of the planar structure of 7 was achieved through conventional NMR and (?)-HR-APCI-MS techniques, and the absolute configuration by comparison of experimental and DFT-calculated ECD spectra. The absolute configuration of 8 was determined using Mosher’s method. Compound 7 showed mild antibacterial activity against Staphylococcus aureus and S. epidermidis . The state of Plocamium taxonomy and its implications upon natural product distributions, especially across samples from specimens collected in different countries, is also discussed.