Cytotoxic ent-Kaurane Diterpenoids from Isodon eriocalyx var. laxiflora

Abstract

Three new ent-kaurane diterpenoids laxiflorin E (1), laxiflorin H (6) and laxiflorin I (8) were isolated from the leaves of Isodon eriocalyx var. laxiflora, along with nine known diterpenoids, eriocalyxin A (2), laxiflorin C (3), laxiflorin D (4), laxiflorin A (5), maoecrystal S (7), maoecrystal Q (9), eriocalyxin B (10), maoecrystal C (11) and enmelol (12). The structures of the new compounds were determined by spectroscopic methods. Compounds 1 - 5 are 6,7-seco-ent-kaurane-7,20-olide diterpenoids, and 6 - 12 belong to 7,20-epoxy-ent-kauranoids. The spectral data of enmelol (12) are reported here for the first time. Ten of these compounds were tested for their cytotoxicity toward K562 and T24 human tumor cells. Compounds 1, 3 and 10 showed significant inhibitory effects on K562 cells with IC₅₀ values 0.077, 0.569 and 0.373 μg/mL, and compounds 1 and 10 also demonstrated significant inhibitory activities toward T24 cells with IC₅₀ values 0.709 and 0.087 μg/mL. Compounds 8 and 11 also displayed inhibitory effect on both two kinds of cells with IC₅₀ value less than 6.5 μg/mL.

Isodon eriocalyx var. laxiflora - Labiatae - laxiflorins E and H-I - ent-kauranoids - cytotoxicity

References

• 1 Fujita E, Node M. Progress in the Chemistry of Organic Natural Products-Diterpenoids of Rabdosia species.  Springer-Verlag,. 1984;  46 77-157
• 2 Wu C Y, Li H W. Angiospermae Dicotylednae Labiatae (2), in Flora Republicae Popularis Sinicae.  Beijing Academic Press, Beijing,. 1987;  66 494
• 3 Shen P Q, Sun H D, Lin Z W. Diterpenoids of Rabdosia eriocalyx var. laxiflora .  Acta Botanica Yunnanica,. 1986;  8 163-6
• 4 Sun H D, Lin Z W, NIU F D, Shen P Q, Pan L T, Lin L Z, Cordell G A. Diterpenoids from Isodon eriocalyx var. laxiflora .  Phytochemistry. 1995;  38 1451-5
• 5 Wang J, Lin Z W, sun H D. Three New 6,7-seco-ent-kaurane diterpenoids from Isodon eriocalyx .  Chinese Chemical Letters. 1997;  8 421-4
• 6 Hou A J, Jiang B, Yang H, Zhao Q S, Lin Z W, Sun H D. A new ent-kauranoid from Isodon eriocalyx var. laxiflora .  Acta Botanic Yunnanica. 2000;  22 337-42
• 7 Wang J, Lin Z W, Tetsuro S, sun H D. Four new compounds from Isodon eriocalyx .  Natural Product Sciences. 1997;  4 143-7
• 8 Wang Z Y, Xu Y L. New diterpenoid constituents of Rabdosia eriocalyx .  Acta Botanica Yunnanica. 1982;  4 407-11
• 9 Li C B, Sun H D, Zhou J. Structures of maoecrystals, New deterpenoids from Rabdosia eriocalyx .  Acta Chimica Sinica. 1988;  46 657-62
• 10 Sachio M, Toru K, Koichi S, Toshihiko O. Studies on the constituents of Isodon trichocarpus Kudo. II. The structures of enmenin, enmelol, and ememodin.  Chem. Pharm. Bull.. 1970;  18 884-9