(±)-Rhodaulision A and B, two pairs of meroterpenoids from branches and leaves of <i>Rhododendron dauricum</i> L. and their anti-osteoarthritis activity

Two pairs of meroterpenoids, (±)-rhodaulision A (<b>1</b>) and B (<b>2</b>) and 8 known compounds [2,7-dimethyl-2-(4-methylpent-3-enyl)-2-chromen-5-ol (<b>3</b>), cannabiorcichromenic acid (<b>4</b>), ranhuadujuanine C (<b>5</b>), ranhuadujuanine D (<b>6</b>), grifolin (<b>7</b>), ilicicolinic acid B (<b>8</b>), anthoponoid H (<b>9</b>), and anthoponoid I (<b>10</b>)] were isolated and identified from the dichloromethane extracts of <i>Rhododendron dauricum</i> L. Meanwhile, extensive spectroscopic methods, NMR and ECD calculations, as well as MS analysis were employed to elucidate the structures of <b>1</b> and <b>2</b>. Subsequently, compounds <b>1-10</b> exhibited a powerful inhibition of osteoclast genesis with an <i>in vitro</i> ratio of more than 90% at 10 μM.