Tabernines A-C, beta-Carbolines from the Leaves of Tabernaemontana elegans

Three novel beta-carboline indole alkaloids (1-3) have been isolated from a MeOH extract of the leaves of Tabernaemontana elegans. The structures were established by means of spectroscopic techniques including 2D NMR experiments. Compounds 1 and 2 contain a two-carbon unit, attached to a structurally related beta-carboline skeleton, as part of an additional six-membered ring in 1 and a seven-membered ring in 2. To the best of our knowledge, this is the first report of beta-carboline indole alkaloids from the genus Tabernaemontana. Compounds 1-3 were evaluated for their ability to modulate multidrug resistance in mouse lymphoma cell lines. Compounds 1 and 3 exhibited a weak activity.. - FCT, Portugal [BPD/30492/2006]. - This study was supported by a fellowship from FCT, Portugal (reference number BPD/30492/2006). The authors wish to thank Dr. T. Vasconcelos of Instituto Superior de Agronomia, Universidade de Lisboa, Portugal, for the taxonomic work on the plant material and also Dr. C. Arruda and Dr. G. de Sousa, from the Portuguese Embassy in Mozambique, as well as the Portuguese Office of International Affairs for plant transport