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

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