Lebbeckoside C, a new triterpenoid saponin from the stem barks of <i>Albizia lebbeck</i> inhibits the growth of human glioblastoma cells

<p>One new acacic acid-type saponin, named lebbeckoside C (<b>1</b>), was isolated from the stem barks of <i>Albizia lebbeck.</i> Its structure was established on the basis of extensive analysis of 1D and 2D NMR (¹H, ¹³C NMR, DEPT, COSY, TOCSY, ROESY, HSQC and HMBC) experiments, HRESIMS studies, and by chemical evidence as 3-<i>O</i>-[<i>β</i>-d-xylopyranosyl-(l→2)-<i>β</i>-d-fucopyranosyl-(1→6)-[<i>β</i>-d-glucopyranosyl(1→2)]-<i>β</i>-d-glucopyranosyl]-21-<i>O</i>-{(2<i>E</i>,6<i>S</i>)-6-<i>O</i>-{4-<i>O</i>-[(2<i>E</i>,6<i>S</i>)-2,6-dimethyl-6-<i>O</i>-(<i>β</i>-d-quinovopyranosyl)octa-2,7-dienoyl]-4-<i>O</i>-[(2<i>E</i>,6<i>S</i>)-2,6-dimethyl-6-<i>O</i>-(<i>β</i>-d-quinovopyranosyl)octa-2,7-dienoyl]-<i>β</i>-d-quinovopyranosyl}-2,6-dimethylocta-2,7-dienoyl}acacic acid 28 <i>O</i>-[<i>β</i>-d-quinovopyranosyl-(l→3)-[<i>α</i>-l-arabinofuranosyl-(l→4)]-<i>α</i>-l-rhamnopyranosyl-(l→2)-<i>β</i>-d-glucopyranosyl] ester. The isolated saponin (<b>1</b>) displayed significant cytotoxic activity against the human glioblastoma cell line U-87 MG and TG1 stem-like glioma cells isolated from a patient tumor with IC₅₀ values of 1.69 and 1.44 μM, respectively.