Two new diterpenoids from the stems of Rhododendron dauricum as GABAA receptor agonists.

Two new diterpenoids, dauricumins A (1) and B (2), together with two known aromatic meroterpenoids (3 and 4), were isolated from the petroleum ether soluble fraction of the stems from Rhododendron dauricum through an HPLC-MS-SPE-NMR combination strategy. The absolute configurations of 1 and 2 were elucidated by ECD calculations and [Rh2 (OCOCF3)4]-induced CD spectrum analysis. In a membrane potential FLIPR assay, confluentin (4) showed an agonistic effect on GABAA receptor (EC50 = 20 µM). [ABSTRACT FROM AUTHOR]