Ent-abietanes from the Godavari mangrove, Ceriops decandra: Absolute configuration and NF-κB inhibitory activity

Nine new ent-abietanes, named decandrols A-I (1-9), which could be categorized into three groups (1, 2-6, 7-9), were isolated from the roots of an Indian mangrove, Ceriops decandra, collected in the swamp of Godavari estuary, Andhra Pradesh, together with six previously reported abietanes (10-15), of which the absolute configurations were first determined. The relative and absolute configurations of these compounds were unambiguously established by HR-ESIMS, extensive 1D and 2D NMR investigations, single-crystal X-ray diffraction analysis with Cu Kα radiation, and quantum-chemical electronic circular dichroism (ECD) calculations. Decandrol A (1) is a rare C₉-spirofused 7,8-seco-ent-abietane, whereas 2-15 are typically tricyclic ent-abietanes. Decandrols C (3) and E (5) exhibited significant NF-κB inhibitory activity at the concentration of 100 μM.