Two new terpenoids from the leaves and twigs of Croton cnidophyllus and their anti-AD activities.

A new oleanane-type triterpenoid, 3β-acetyl-15α-hydroxy-oleanane-13β,28-olide (1), and a new clerodane furanoditerpenoid, cnidophyllin A (2), together with eleven known compounds (3-13) were isolated and identified from the 95% EtOH extract of the leaves and twigs of Croton cnidophyllus. Except for compounds 3 and 7, all other compounds were isolated for the first time from C. cnidophyllus. The structures of the new compounds were ascertained through a comprehensive application of spectroscopic techniques, including both 1D and 2D NMR, IR, and HR-ESI-MS, while their absolute configurations were validated either through single-crystal X-ray diffraction analysis or via electronic circular dichroism (ECD) calculations. Meanwhile, the single-crystal X-ray diffraction data of 8 has been reported for the first time. Additionally, the in vivo anti-Alzheimer's disease (AD) activities of compounds 3-13 were assessed using the Caenorhabditis elegans AD pathology model. Among all the isolated compounds, compounds 4 and 7-13 significantly delayed the paralysis of the worms with AD-like symptoms, which may be potential candidates for anti-AD drugs.