Two new iridoids and triterpenoid analogues from the leaves of Viburnum chingii and their anti-acetylcholinesterase activity

Two undescribed split-ring iridoids (1-2) with six known triterpenes (3-8) and one steride (9) were isolated from the Viburnum chingii. Compound 2 possessed an unprecedented split-ring iridoid skeleton formed by electrocyclic reaction and split ring. The structures and absolute configurations of the new iridoids were established by NMR, HRESIMS, and ECD calculations. All the isolated compounds were tested for AChE inhibitory activity. Biologically, 1, 2, 3, 4, and 7 displayed significant AChE effects compared to the positive control donepezil, and have also been subjected to molecular docking studies.