Caesalminaxins O-T, cassane diterpenoids from the seeds of Caesalpinia minax and their anti-inflammation

Six previously undescribed cassane diterpenoids, named caesalminaxins O-T (1-6), together with 28 known compounds (7-34), were isolated from the seeds of Caesalpinia minax Hance. Their structures, including their absolute configurations were elucidated by extensive spectroscopic analysis, X-ray diffraction, and quantum chemical calculations. Among the undescribed diterpenoids, compound 6 that possessed an unusual enol group at C-7 with a highly deshielded 1H NMR signal was the first example in cassane diterpenoids. All of the isolates were evaluated for their inhibitory activity against lipopolysaccharide-activated NO production in RAW264.7 cells. Compound 16 showed moderate inhibitory activity with an IC50 value of 17.3 μM, which was more potent than the positive control (indomethacin, IC50 = 29.7 μM).