Abstract: A new ent-spirokaurenc diterpene, guidongnin ( 1 ) , mp 235- 237°C,[α]22/D -160°(C = 1, pyridine), was isolated from the ether extract of dried leaves of Rabdosia rubescens (Hemsl.) Hara (Labiatae)that collected in Guizhou, China. Its structure has been shown to be ent-6 , 7 -spiroseco- 6 , 19 -γ-lactonic ring-7 , 20-δ-lactonic ring-16-kaurene-11β, 15α-diol ( 1 ) on the basis of spectroscopic and chemical evidence and compared with known compound, ludo-ngnin A. Two known spirokauranoids, ludongnin A ( 2 ) and B ( 3 ) were also isolated together with β-sitosterol, R-sitosterol-D-glucoside, 2α-hydroxyursolic acid and cirsiliol.

Key words: Diterpenoid