Cassane-type diterpenoids from Caesalpinia echinata (Leguminosae) and their NF-κB signaling inhibition activities.

Fourteen cassane-type diterpenoids, echinalides H-U, were isolated from the stem of Caesalpinia echinata Lam. (Leguminosae). The structures of the echinalides were elucidated by spectroscopic investigation, including 2D NMR spectroscopic analysis. The structures of echinalide H and echinalide T were further confirmed by single-crystal X-ray diffraction. The absolute configurations of echinalides H, I, J and K were determined by CD spectroscopy. Additionally, the absolute configurations of echinalide L and M were determined by chemical conversion from echinalide H. These compounds were evaluated for inhibitory activity against nuclear factor κB (NF-κB). Echinalide M showed the most potent inhibitory activity (47±11% at 5μM) toward NF-κB-responsive gene expression.