Terpenoids from the Soft Coral Sinularia sp. Collected in Yongxing Island.

Three new sesquiterpenoids (sinuketal (<bold>1</bold>), sinulins A and B (<bold>2</bold> and <bold>3</bold>)) and two new cembranoids (sinulins C and D (<bold>4</bold> and <bold>5</bold>)), as well as eight known sesquiterpenoids (<bold>6–13</bold>) and eight known cembranoids (<bold>14–21</bold>), were isolated from the Xisha soft coral <italic>Sinularia</italic> sp. Their structures were elucidated by extensive spectroscopic analysis. Compound <bold>1</bold> possesses an unprecedented isopropyl-branched bicyclo [6.3.0] undecane carbon skeleton with unique endoperoxide moiety, and a plausible biosynthetic pathway of it was postulated. According to the reported biological properties of endoperoxide, the antimalarial, cytotoxic, antiviral, and target inhibitory activities of <bold>1</bold> were tested. Compound <bold>1</bold> showed mild in vitro antimalarial activity against <italic>Plasmodium falciparum</italic> 3D7, weak cytotoxic activities toward Jurkat, MDA-MB-231, and U2OS cell lines, inhibitory effects against influenza A viruses H1N1 and PR8, as well as mild target inhibitory activity against acetylcholinesterase. The other compounds were evaluated for cytotoxicities against HeLa, HCT-116, and A549 tumor cell lines and target inhibitory activities against protein tyrosine phosphatase 1B (PTP1B). Compound <bold>20</bold> exhibited cytotoxicities against HeLa and HCT-116, and compounds <bold>5</bold>, <bold>11</bold>, and <bold>15</bold> showed mild target inhibitory activities against PTP1B. [ABSTRACT FROM AUTHOR]