Alkaloids and Polyacetylenes from Hippobroma longiflora with Antiangiogenesis Properties

Four new alkaloids, hippobrines A–D (1–4), along with three new polyacetylenes, hippobrenes A–C (5–7), were isolated from Hippobroma longiflora. Compounds 1–3 possess an unprecedented carbon skeleton. All of the new structures were determined by analyzing their mass and NMR spectroscopic data. The absolute configurations of 1 and 2 were confirmed by single-crystal X-ray analyses, and the absolute configurations of 3 and 7 were deduced using their ECD spectra. Plausible biogenetic pathways of 1 and 4 were proposed. In regard to bioactivities, all compounds (1–7) exhibited weak antiangiogenic activity against human endothelial progenitor cells, with IC50 values ranging from 21.1 ± 1.1 to 44.0 ± 2.3 μg/mL.