Bioactivity-guided isolation of potent inflammasome and mitochondria damage inhibitory diterpenoids from Orthosiphon...

Orthosiphon wulfenioides is a medicinal plant to treat arthritis, vascular inflammation, edema, and dyspepsia. To explore the anti-inflammatory components and their mechanism of action, 12 previously undescribed highly oxidized diterpenes, wulfenioidones L-W (1-12), were isolated from O. wulfenioides by bioactivity orientation. Their structures were elucidated using HRESIMS, NMR, specific rotation, single-crystal X-ray diffraction, and ECD spectra analysis. Compounds 1-4 exhibited significant inhibition on LDH release by preventing macrophage J774A.1 pyroptosis. Compound 1 showed the most potent inhibitory effect with an IC₅₀ value of 5.81 μM. It was revealed in the Western blot experiment that compound 1 not only significantly and dose-dependently decreased the activation of CASP1 and IL-1β, but also prevented GSDMD-FL from splitting into GSDMD-NT, the membrane pore-forming protein to release inflammatory factors, thus blocking the extracellular release of IL-1β. More interestingly, compound 1 not only blocked the activation of NLRP3 inflammasome, but also strikingly enhanced the orange fluorescence of JC-1 aggregates, thus showing the activity of maintaining mitochondrial membrane potential and reversing mitochondria damage.