A methanol extract of the stem bark
of the Malayan Alstonia
penangiana provided seven new bisindole alkaloids, comprising
six macroline–sarpagine alkaloids (angustilongines E–K, 1–6) and one macroline–pleiocarpamine
bisindole alkaloid (angustilongine L, 7). Analysis of
the spectroscopic data (NMR and MS) of these compounds led to the
proposed structures of these alkaloids. The macroline–sarpagine
alkaloids (1–6) showed in vitro growth
inhibitory activity against a panel of human cancer cell lines, inclusive
of KB, vincristine-resistant KB, PC-3, LNCaP, MCF7, MDA-MB-231, HT-29,
HCT 116, and A549 cells (IC50 values: 0.02–9.0 μM).
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