Abstract
In addition to 13 known compounds, four new bisabolane sesquiterpenes, okamurenes A–D (1–4), a new chamigrane derivative, okamurene E (5), and a new C12-acetogenin, okamuragenin (6), were isolated from the marine red alga Laurencia okamurai. The structures of these compounds were determined through detailed spectroscopic analyses. Of these, okamurenes A and B (1 and 2) are the first examples of bromobisabolane sesquiterpenes possessing a phenyl moiety among Laurencia-derived sesquiterpenes, while okamuragenin (6) was the first acetogenin aldehyde possessing a C12-carbon skeleton. Each of the isolated compounds was evaluated for the brine shrimp (Artemia salina) lethal assay and 7-hydroxylaurene displayed potent lethality with LD50 1.8 μM.
Highlights
Marine red algae of the genus Laurencia are prolific sources of diversified secondary metabolites, predominantly sesquiterpenoids, diterpenoids, and nonterpenoid C15-acetogenins [1]
In the past five years, we have systematically conducted chemical investigation towards eight Laurencia species, which have resulted in the isolation of more than 30 new compounds [2,7,8,9,10,11]
Continuous effort on the chemical investigation of this algal species collected from Weihai coastline resulted in the isolation and identification of five new sesquiterpenes, okamurenes A–E (1–5), one new C12-acetogenin, okamuragenin (6) (Figure 1), as well as nine known sesquiterpenes and four known C15-acetogenins
Summary
Marine red algae of the genus Laurencia are prolific sources of diversified secondary metabolites, predominantly sesquiterpenoids, diterpenoids, and nonterpenoid C15-acetogenins [1]. These compounds, with structurally diverse skeletons, have attracted much. In the past five years, we have systematically conducted chemical investigation towards eight Laurencia species, which have resulted in the isolation of more than 30 new compounds [2,7,8,9,10,11]. Continuous effort on the chemical investigation of this algal species collected from Weihai coastline resulted in the isolation and identification of five new sesquiterpenes, okamurenes A–E (1–5), one new C12-acetogenin, okamuragenin (6) (Figure 1), as well as nine known sesquiterpenes and four known C15-acetogenins. We present the isolation, structure elucidation, and bioactivity of these compounds
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