Isolation of nor-secofriedelanes from the sedative extracts of Galphimia glauca.
Preparative-scale recycling HPLC was used for the complete resolution of a complex mixture of nor-secofriedelanes into five major peaks (I-V) from the sedative methanolic extracts prepared from the aerial parts of Galphimia glauca. Argentation chromatography was used to show peaks I, II, IV, and V to be mixtures of isomers around the E-ring double bond, represented by the endocyclic C-20, C-21 double-bond isomers, galphimines A (3), B (1), D (4), and E (2), and the C-20, C-29 exocyclic forms, galphimines F-I (5-8). Galphimine C (9), isolated from peak III, corresponded to the C-19, C-20 double-bond isomer of the previously known major sedative constituent galphimine B. The characterization of all the new triterpenes (3-9) was performed primarily by high-field NMR spectroscopy. Comparison between experimental and calculated (1)H-(1)H vicinal coupling constants and the analysis of molecular mechanics structures revealed that the ring B of these compounds exists in a boatlike conformation. The absolute configuration for the stereogenic carbinol center at C-4 was established by the application of the Mosher ester derivatization technique carried out in NMR tubes.
Cardoso Taketa
Alexandre T
AT
Departamento de Farmacia, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City 04510, Mexico.
Lozada-Lechuga
Jorge
J
Fragoso-Serrano
Mabel
M
Villarreal
María Luisa
ML
Pereda-Miranda
Rogelio
R
D002851:Chromatography, High Pressure Liquid; D031582:Galphimia / Q000737:chemistry*; D006993:Hypnotics and Sedatives / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D008800:Mexico; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010946:Plants, Medicinal / Q000737:chemistry*; D014315:Triterpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology
D006993:Hypnotics and Sedatives; D014315:Triterpenes; C084708:galphimine B