| Summary: | A chemical study on the extracts of soft coral <i>Lemnalia bournei</i> resulted in the isolation and identification of six new bicyclic diterpene glycosides including three new lemnaboursides E–G (<b>1</b>–<b>3</b>), and three new lemnadiolboursides A–C (<b>4</b>–<b>6</b>), along with three known lemnaboursides (<b>7</b>–<b>9</b>). Their structures were elucidated by detailed spectroscopic analysis, ECD analysis, chemical methods, and comparison with the literature data. Lemnadiolboursides A–C (<b>4</b>–<b>6</b>) contained a lemnal-1(10)-ene-7,12-diol moiety compared with the lemnaboursides. All these compounds were evaluated for antibacterial activity; cell growth inhibition of A549, Hela, HepG2, and CCRF-CEM cancer cell lines; and inhibition of LPS-induced NO production in RAW264.7 macrophages. The results indicated that compounds <b>1</b>, <b>2</b>, and <b>4</b>–<b>6</b> exhibited antibacterial activity against <i>Staphylococcus aureus</i> and <i>Bacillus subtilis</i> (MIC 4–16 μg/mL); compounds <b>1</b>–<b>9</b> displayed low cytotoxicity on the CCRF-CEM cell lines (IC<sub>50</sub> 10.44–27.40 µM); and compounds <b>1</b>, <b>2,</b> and <b>5</b> showed weak inhibition against LPS-induced NO production (IC<sub>50</sub> 21.56–28.06 μM).
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