Highly oxygenated clerodane furanoditerpenoids from the leaves and twigs of Croton yunnanensis

The phytochemical investigation of the leaves and twigs of Croton yunnanensis led to the isolation of eight new clerodane furanoditerpenoids, croyunfuranoids A−H ( 1 − 8 ), together with three known analogues ( 9 − 11 ). The structures were elucidated by spectroscopic analyses, and their absolute configurations were determined by a combination of ECD calculations and single-crystal X-ray diffraction. Croyunfuranoid D ( 4 ) represents a rare 18,19-dinor-clerodane diterpenoid. Besides, the structure of a previously reported diterpenoid, crotonyunnan B, was revised. All compounds were tested for their inhibitory activities on nitric oxide (NO) production in LPS-induced RAW 264.7 macrophages, and compounds 5 and 6 exhibited potential inhibitory effects with IC₅₀ values of 20.33 ± 2.31 and 22.80 ± 1.31 μM, respectively.