Alstilobanines A–E, new indole alkaloids from Alstonia angustiloba

Five new alkaloids, alstilobanines A (1)–E (5) were isolated from Alstonia angustiloba (Apocynaceae) and their structures were determined by MS and 2D NMR spectral analysis. Alstilobanines A–E showed a moderate vasorelaxant activity against phenylephrine-induced contraction of isolated rat aorta.

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