Ent-kauranes from the Chinese Excoecaria agallocha L. and NF-κB inhibitory activity

Eleven undescribed ent-kauranes, named agallochanins A-K, were isolated from the stems and twigs of the Chinese semi-mangrove plant, Excoecaria agallocha L.. The absolute configurations of these diterpenoid compounds, except for the chirality of C-4 in agallochanin H, were unequivocally determined by HR-ESIMS, extensive NMR investigations, single-crystal X-ray diffraction analyses with Cu Kα radiation, quantum-chemical electronic circular dichroism (ECD) calculations, the comparison of experimental ECD spectra, and the modified Mosher's α-methoxy-α-(trifluoromethyl)phenylacetyl (MTPA) ester method. Agallochanins A-I are 3,4-seco-ent-kauranes. Agallochanin D represents the first example of 3,4-seco-17-nor-ent-kaurane. Agallochanin K exhibited NF-κB inhibitory activity with the inhibition rate of 79.6% at the concentration of 100.0 μM.