Discovery of Cyclic Diarylheptanoids as Inhibitors against Influenza A Virus from the Roots of <i>Casuarina equisetifolia</i>.
Xu X, Chen L, Luo Y, Gao R, Xu Y, Yang J, Zhou Z, Wei X.
Four new cyclic diarylheptanoids, casuarinols A-C (<b>1</b>-<b>3</b>) and casuarinolide A (<b>4</b>), together with six known ones (<b>5</b>-<b>10</b>), were isolated from the roots of <i>Casuarina equisetifolia</i>. Structures were elucidated by extensive spectroscopic analysis, theoretical conformational, and electronic circular dichroism analyses. Casuarinol C (<b>3</b>) is a novel cyclic diarylheptanoid-aldehyde adduct. Casuarinolide A (<b>4</b>) represents the first structure of a <i>seco</i>-cyclic diarylheptanoid. Compounds <b>1</b>-<b>9</b> were evaluated for their anti-influenza A virus (IAV) activity against A/WSN/33 (H1N1). (-)-(<i>M</i>)-11-Oxo-3,12<i>R</i>,17-trihydroxy-9-ene-[7,0]-metacyclophane (<b>5</b>) displayed significant anti-IAV activity with an IC<sub>50</sub> value of 8.64 ± 2.49 μM and a CC<sub>50</sub> higher than 100 μM.