Triterpenoid saponins from the buds of <i>Lonicera similis</i>

<p>Four new lupane triterpenoid saponins, along with one known lupane and eight hederagenin saponins, were isolated from the EtOH extract of the buds of <i>Lonicera similis</i> Hemsl. The structures of the new compounds were established as 3-<i>O</i>-<i>β</i>-D-glucopyranosyl-(1→2)-<i>β</i>-D-glucopyranosyl 23-hydroxybetulinic acid 28-<i>O</i>-<i>β</i>-D-glucopyranosyl ester (lonisimilioside A, <b>1</b>), 3-<i>O</i>-<i>β</i>-D-glucopyranosyl-(1→2)-<i>β</i>-D-glucopyranosyl 23-hydroxybetulinic acid 28-<i>O</i>-<i>β</i>-D-glucopyranosyl-(1→6)-<i>β</i>-D-glucopyranosyl ester (lonisimilioside B, <b>2</b>), 3-<i>O</i>-<i>β</i>-D-glucopyranosyl-(1→2)-<i>β</i>-D-glucopyranosyl betulinic acid 28-<i>O</i>-<i>β</i>-D-glucopyranosyl-(1→6)-<i>β</i>-D-glucopyranosyl ester (lonisimilioside C, <b>3</b>) and 3-<i>O</i>-<i>β</i>-D-glucopyranosyl-(1→2)-<i>β</i>-D-glucopyranosyl-(1→6)-<i>β</i>-D-glucopyranosyl betulinic acid 28-<i>O</i>-<i>β</i>-D-glucopyranosyl ester (lonisimilioside D, <b>4</b>), respectively. The cytotoxic activities of the isolates against human cancer cell lines HepG2, MCF-7 and A-549 were evaluated. Only the monodesmosidic saponin with a free carboxyl group at C-28 (<b>12</b>) exhibited significant cytotoxicities against HepG2, MCF-7 and A-549 cell lines with the IC<sub>50</sub> values of 8.98 ± 0.19, 12.48 ± 0.45 and 11.62 ± 0.54 μM, respectively. Furthermore, Hoechst fluorescence 33342 staining was used to demonstrate that <b>12</b> could induce HepG2 and A-549 cells apoptosis significantly.</p>