title: ent-kaurane and ent-pimarane diterpenoids from Siegesbeckia pubescens.
abstract: Phytochemical investigation of the above-ground parts of Siegesbeckia pubescens yielded 25 diterpenoids, including five new ent-pimarane diterpenoids (1-3, 11, and 12) and four new ent-kaurane diterpenoids (13-16). The structures and relative configurations of the new compounds were elucidated by comprehensive spectroscopic analysis and by comparison of their NMR data with those of related compounds. Single-crystal X-ray diffraction analysis confirmed the structures of 8, 13, and 14. Seven of these diterpenoids were evaluated for cytotoxic activity against HSC-T6, HeLa, and B16 cell lines. Compounds 11 and 14 exhibited moderate cytotoxicity.
authors.affiliation: State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People's Republic of China.
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.forename: Wen-Hao
authors.initials: WH
authors.lastname: Chen
authors.forename: Yan-Ping
authors.initials: YP
authors.lastname: Shi
mesh_terms: D045784:Abietanes / Q000737:chemistry*; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D019659:Asteraceae / Q000737:chemistry*; D018360:Crystallography, X-Ray; D045786:Diterpenes, Kaurane / Q000737:chemistry*; D004354:Drug Screening Assays, Antitumor; D004365:Drugs, Chinese Herbal / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D006801:Humans; D008968:Molecular Conformation; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular
chemical_list: D045784:Abietanes; D000972:Antineoplastic Agents, Phytogenic; D045786:Diterpenes, Kaurane; D004365:Drugs, Chinese Herbal; C433018:pimarane