Strophioglandins A–C, highly rearranged norditerpenoids with an unusual tricyclo[6.4.1.04,13]tridecane core from Strophioblachia glandulosa var. cordifolia

Strophioglandins A-C (1-3), three highly rearranged norditerpenoids featuring an unusual tricyclo[6.4.1.04,13]tridecane core, were isolated from Strophioblachia glandulosa var. cordifolia. Integrated spectroscopic analyses, X-ray crystallography, and ECD calculations synergistically determined their molecular architectures. Remarkably, all compounds manifested potent anti-inflammatory effects in LPS-activated RAW264.7 cells with IC50 values ranging from 7.83 ± 1.11 to 15.09 ± 1.21 μM. Mechanism study revealed that strophioglandin A (1), the most potent compound, could suppress the expression of multiple inflammatory factors by inhibiting the P38 and Erk1/2 MAPK signaling pathways.