16,17-dinor-abietane diterpenoids from Casearia kurzii

Eleven undescribed 16,17-dinor-abietane diterpenoids, caseazins A-K (1−11), and ten known diterpenoids (12−21) were isolated from the twigs and leaves of Casearia kurzii (Flacourtiaceae). Caseazins A-K were the first abietane -type dinorditerpenoids to have been isolated from the plant of Casearia kurzii. Their chemical structures were elucidated using a combination of 1D and 2D NMR spectroscopy and mass spectrometry. The absolute configurations of 5 and 10 were established by electronic circular dichroism calculations. Moreover, compounds 2, 3, 13, 14, and 18 exhibited anti-inflammatory activity with IC50 values of 0.17, 0.36, 6.55, 1.30, and 4.53 μM, respectively. IL-1β and caspase-1 analyses suggested that compound 14 inhibited NLRP3 inflammasome activation and blocked macrophage pyroptosis.