title: New cytotoxic clerodane diterpenoids from the leaves and twigs of Casearia membranacea.
abstract: Bioassay-guided fractionation of an EtOAc-soluble extract of Casearia membranacea has resulted in the isolation of six new clerodane diterpenes, caseamembrins A-F (1-6), and a known compound, rel-(2S,5R,6R,8S,9S,10R,18S,19R)-diacetoxy-18,19-epoxy-6-hydroxy-2-(2-methylbutanoyloxy)cleroda-3,13(16),14-triene (7). The structures of 1-6 were established on the basis of extensive 1D and 2D NMR spectroscopic analysis. In addition, the new derivatives, 8 and 9, were prepared by acylation of 7 and 3, respectively. The isolated diterpenoids and their derivatives were tested against human prostate (PC-3) and hepatoma (Hep3B) cancer cells. Compounds 1, 3-5, and 7 exhibited cytotoxicity against both tumor cells, with IC(50) values below 3 micromicro, while compounds 2, 6, 8, and 9 were less effective.
authors.affiliation: Institute of Marine Resources, National Sun Yat-sen University, 70 Lien-Hai Road, Kaohsiung, Taiwan, Republic of China.
authors.forename: Ya-Ching
authors.initials: YC
authors.lastname: Shen
authors.forename: Chih-Hsin
authors.initials: CH
authors.lastname: Wang
authors.forename: Yuan-Bin
authors.initials: YB
authors.lastname: Cheng
authors.forename: Li-Tung
authors.initials: LT
authors.lastname: Wang
authors.forename: Jih-Hwa
authors.initials: JH
authors.lastname: Guh
authors.forename: Ching-Te
authors.initials: CT
authors.lastname: Chien
authors.forename: Ashraf Taha
authors.initials: AT
authors.lastname: Khalil
mesh_terms: D000107:Acetylation; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D037821:Casearia / Q000737:chemistry*; D045785:Diterpenes, Clerodane / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D020128:Inhibitory Concentration 50; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D018515:Plant Leaves / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry*; D013624:Taiwan; D014407:Tumor Cells, Cultured
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D045785:Diterpenes, Clerodane