title: Ibogan, Aspidosperman, Vincamine, and Bisindole Alkaloids from a Malayan Tabernaemontana corymbosa: Iboga Alkaloids with C-20α Substitution.
abstract: Ten new indole alkaloids (1-10) comprising five ibogan, two aspidosperman, one vincamine, and two bisindole alkaloids, in addition to 32 known alkaloids, were isolated from the stem-bark extract of a Malayan Tabernaemontana corymbosa. The structures of these alkaloids were determined based on analysis of the NMR and MS data and, in five instances (1, 3, 5, 6, 8), confirmed by X-ray diffraction analysis. Two of the iboga alkaloids, conodusines B (2) and C (3), and the iboga-containing bisindole tabernamidine B (10) are notable for the presence of an α-substituted acetyl group at C-20 of the iboga carbon skeleton. The iboga alkaloid (+)-conodusine E (5) had MS and NMR data that were identical to those of (-)-ervatamine I, recently isolated from Ervatamia hainanensis. Establishment of the absolute configuration of (+)-conodusine E (5) was based on analysis of the ECD data, correlation with (-)-heyneanine, and X-ray analysis, which showed that (+)-5 belongs to the same enantiomeric series as exemplified by (-)-coronaridine. The configuration at C-20' of the previously reported Tabernaemontana bisindole alkaloid 19'-oxotabernamine (renamed tabernamidine B) required revision based on the present results. Several of the bisindoles showed pronounced in vitro growth inhibitory activity against drug-sensitive and vincristine-resistant KB cells.
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya , 50603 Kuala Lumpur, Malaysia.
authors.forename: Choy-Eng
authors.initials: CE
authors.lastname: Nge
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya , 50603 Kuala Lumpur, Malaysia.
authors.forename: Kam-Weng
authors.initials: KW
authors.lastname: Chong
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya , 50603 Kuala Lumpur, Malaysia.
authors.forename: Noel F
authors.initials: NF
authors.lastname: Thomas
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya , 50603 Kuala Lumpur, Malaysia.
authors.forename: Siew-Huah
authors.initials: SH
authors.lastname: Lim
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya , 50603 Kuala Lumpur, Malaysia.
authors.forename: Yun-Yee
authors.initials: YY
authors.lastname: Low
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya , 50603 Kuala Lumpur, Malaysia.
authors.forename: Toh-Seok
authors.initials: TS
authors.lastname: Kam
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry; D018360:Crystallography, X-Ray; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D007050:Ibogaine / Q000031:analogs & derivatives; D026121:Indole Alkaloids / Q000737:chemistry* / Q000302:isolation & purification*; D007624:KB Cells; D008968:Molecular Conformation; D015394:Molecular Structure; D024301:Plant Bark / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D030014:Tabernaemontana / Q000737:chemistry; D014749:Vincamine / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D014750:Vincristine / Q000494:pharmacology
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D026121:Indole Alkaloids; D007050:Ibogaine; C011734:coronardine; D014750:Vincristine; D014749:Vincamine