Oleanane-type triterpenoids from Sabia limoniacea with nitric oxide inhibitory activity

Fourtheen undescribed oleanane-type triterpenoids (Sabialimons S-Z₆), including five nortriterpenoids (1-5) and nine normal triterpenoids (6-14), along with five previously described analogs (15-19) were isolated and characterized from the stems of Sabia limoniacea. Their structures were fully elucidated via extensive spectroscopic analyses, including 1D and 2D NMR, HRESIMS. Compounds 1-3 are oleanane-type triterpenoids which the rings A are broken and the carbons of position 2 are absent to form the five-membered ring-A contracted nortriterpenoids, resulting in the establishment of a 5/6/6/6/6 pentacyclic skeleton. Compounds 4 and 5 represent the interesting variation in which the C-1/C-3 bonds have been oxidatively cleaved to generate ring-A-seco triterpenoids, leading to establishment of a 0/6/6/6/6 tetracyclic skeleton. Biological evaluation revealed that compounds 9 and 10 can inhibited nitric oxide production in lipopolysaccharide stimulated RAW264.7 cells with IC₅₀ values of 36.40 and 36.52 μM, respectively.