title: New cytotoxic bis-labdanic diterpenoids from Alpinia calcarata.
abstract: Two novel bis-labdanic diterpenoids named calcaratarin D and calcaratarin E were isolated from the rhizomes of Alpinia calcarata. Their structures were elucidated as a pair of stereoisomers on the basis of the spectral evidence. 2D NMR techniques including (1)H- (1)H COSY, HMQC, HMBC, NOESY spectra and HRFABMS were extensively applied to establish the structures. The two bis-labdanic diterpenoids showed cytotoxic activity against human KB cells in vitro.
mesh_terms: D032429:Alpinia; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D004224:Diterpenes / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D020128:Inhibitory Concentration 50; D007624:KB Cells; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010936:Plant Extracts / Q000494:pharmacology; D013237:Stereoisomerism
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004224:Diterpenes; D010936:Plant Extracts; C469368:calcaratarin D; C469367:calcaratarin E; C433017:labdane