New Diterpenoids from Tricalysia dubia

Tricalysia dubia (Rubiaceae), an evergreen shrub or tree, is widely distributed in Taiwan, the southern parts of China and Japan. From the leaves of this plants, unique rearranged ent-kaurane glycosides A – G, and the ent-kaurane glycosides H – O, have been isolated. In our presentation, six rearranged ent-kaurane diterpenes, tricalysiolides A – F [1], tricalysiamides A – D [2], tricalysiolide H, tricalysiones A and B [3], and a known diterpene, cafestol from the wood of this plant are reported, especially their cytotoxic activity against P388 leukemia cells in mice as well as the structure elucidation using spectral analyses and chemical methods. References: [1] Nishimura, K. et al. (2006), Tetrahedron, 62, 1512. [2] (2007) J. Nat. Prod., in press. [3] (2007) Tetrahedron, in press.