Callintegers A and B, Unusual Tricyclo[4.4.0.0 9,10 ]tetradecane Clerodane Diterpenoids from Callicarpa integerrima with Inhibitory Effects on NLRP3 Inflammasome Activation.

Callintegers A ( 1 ) and B ( 2 ), unprecedented clerodane norditerpenoids based on a novel carbon skeleton, were isolated from Callicarpa integerrima . Compounds 1 and 2 possess a novel 6/6/6-fused tricyclic ring system. Their structures and absolute configurations were determined by quantum chemical calculations, spectroscopic analysis, and single-crystal X-ray diffraction methods. Biological evaluation showed that compound 2 inhibited IL-1β secretion in a dose-dependent manner with an IC 50 value of 5.5 ± 3.2 μM. Caspase-1 maturation and IL-1β secretion were also reduced, indicating that compound 2 impaired NLRP3 inflammasome activation.