title: 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 microg/mL, and compounds 1 and 10 also demonstrated significant inhibitory activities toward T24 cells with IC50 values 0.709 and 0.087 microg/mL. Compounds 8 and 11 also displayed inhibitory effect on both two kinds of cells with IC 50 value less than 6.5 microg/mL.
authors.affiliation: Laboratory of Phytochemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, P R China.
authors.forename: Xue-Mei
authors.initials: XM
authors.lastname: Niu
authors.forename: Sheng-Hong
authors.initials: SH
authors.lastname: Li
authors.forename: Ma-Lin
authors.initials: ML
authors.lastname: Li
authors.forename: Qin-Shi
authors.initials: QS
authors.lastname: Zhao
authors.forename: Shuang-Xi
authors.initials: SX
authors.lastname: Mei
authors.forename: Zhi
authors.initials: Z
authors.lastname: Na
authors.forename: Su-Jun
authors.initials: SJ
authors.lastname: Wang
authors.forename: Zhong-Wen
authors.initials: ZW
authors.lastname: Lin
authors.forename: Han-Dong
authors.initials: HD
authors.lastname: Sun
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D004224:Diterpenes / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D006801:Humans; D020128:Inhibitory Concentration 50; D020014:K562 Cells; D019686:Lamiaceae; D009682:Magnetic Resonance Spectroscopy; D014407:Tumor Cells, Cultured
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004224:Diterpenes; C465090:enmelol; C465087:laxiflorin E; C465088:laxiflorin H; C465089:laxiflorin I