Diterpenoids from Callicarpa rubella and their in vitro anti-NLRP3 inflammasome activity

Nine new diterpenoids, Rubellacrns A - I (1-9), including five isopimaranes (1-4, 9), four pimaranes (5-8), together with five known isopimarane analogues (10-14), were isolated from Callicarpa rubella. The structures of these compounds were unambiguously established by HR-ESIMS and NMR spectroscopic data, the absolute configurations of compounds 5 and 9 were determined by ECD. All the isolated compounds were tested for their anti-inflammatory effects and compounds 2 and 11-14 showed NLRP3-inflammasome inhibitory activity with IC₅₀ values ranging from 7.02 to 14.38 μM.