Pentacyclic Triterpenoids from Sabia discolor Dunn and Their α-Glycosidase Inhibitory Activities

Four new pentacyclic triterpenoids named Sabiadiscolor A–D (1 and 7–9) together with eleven known ones were isolated by repeated column chromatography. Their structures were identified and characterized by NMR and MS spectral data as 6 oleanane-type pentacyclic triterpenoids (1–6), 7 ursane-type ones (7–13), and 2 lupanane-type ones (14–15). Except for compound 15, all other compounds were isolated from Sabia discolor Dunn for the first time. Their α-glycosidase inhibitory activities were evaluated, which showed that compounds 1, 3, 8, 9, 13, and 15 implied remarkable activities with IC(50) values ranging from 0.09 to 0.27 μM, and the preliminary structure–activity relationship was discussed.