| Three plants, Phlogacanthus curviflorus (Wall) Nees, Daphne tangutica Maxim and Cipadessa cinerascens (Pell.) Hand-Mazz, were chemically studied. 1. From the roots of Phlogacanthus curviflorus (Wall) Nees, two new diterpene lactones, phlogacantholides B (1) and C (2), and three new diterpene lactone glucosides, phlogacanthosides A (3), B (4) and C (5) were isolated, together with lupeol (6), betulin (7), β-sitosterol (8), β-daucosterol (9), (+)-syringaresinol (10) and (+)-syringaresinol-4-O-β-D-glucopyranoside (11). Their structures were elucidated by chemical and spectroscopic evidence. The structure of phlogacantholide B (1) was confirmed by X-ray crystallographic analysis of its diacetate (6). At a concentration of 7.0 mg/mL, phlogacantholides B (1) showed penicillin augment activity, which was equivalent to clavulanic acid at a concentation of 849 μg/mL. 2. The in vitro and in vivo test indicated that the 95% ethanol extracts of Daphne tangutica Maxim showed obvious antidiabetic activity in amending insulin resistance. Fourteen known compounds were obtained from petroleum ether fraction, which showed strong antidiabetic activity in vitro. All of the isolated compounds are inactive. 3. Six new tetranortriterpenoids, cipadesin A (24), cipadesin B (25), cipadesin C (26), cipadesin D (27), cipadesin E (28) and cipadesin F (29), together with β-sitosterol (8), β-daucosterol (9) and 8,15-dihydroxy-13E-labdane (30), were isolated from the 95% ethanol extracts of the aerial parts of Cipadessa cinerascens. Their structures were elucidated by spectroscopic evidence. X-ray crystallographic analysis confirmed the structures of 24 and 26. Compounds 26-28 possess novel skeletons. 4. New tetranortriterpenoids and their bioactivities reported from 1999 to 2005 were summarized.
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