Structures and Antiproliferative Activity of Saponins from Sechium pittieri and S. talamancense

抄録

Six bisdesmosidic bayogenin saponins, named tacacosides A₁, A₂, B₁, B₂, B₃ and C, were isolated from the fruit and aerial parts of Sechium pittieri (COGN.) C. KEFFREY and S. talamancense (WUNDERLIN) C. JEFFREY, Costa Rican cucurbitaceae plants. Their structures were elucidated based on spectral and chemical evidence as follows. Tacacoside A₁ : 3-O-[β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl]bayogenin 28-O-{α-L-rhamnopyranosyl-(1→3)-β-D-xylopyranosyl-(1→4)-β-D-apiofuranaosyl-(1→3)]-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl} ester, tacacoside A₂ : 3-O-[β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl]bayogenin 28-O-{α-L-rhamnopyranosyl-(1→3)-β-D-xylopyranosyl-(1→4)-[β-D-xylopyranosyl-(1→3)]-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl} ester, tacacoside B₁ : 3-O-[β-D-glucopyranosyl]bayogenin 28-O-{α-L-rhamnopyranosyl-(1→3)-β-D-xylopyranosyl-(1→4)-[β-D-apiofuranosyl-(1→3)]-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl} ester, tacacoside B₂ : 3-O-[β-D-glucopyranosyl]bayogenin 28-O-{α-L-rhamnopyranosyl-(1→3)-β-X-xylopyranosyl-(1→4)-[β-D-xylopyranosyl-(1→3)]-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl} ester, tacacoside B₃ : 3-O-[β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl]bayogenin 28-O-[α-L-rhamnopyranosyl-(1→3)-β-D-xylopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl] ester, and tacacoside C : 3-O-[β-D-glucopyranosyl]bayogenin 28-O-[α-L-rhamnopyranosyl-(1→3)-β-D-xylopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl] ester. These saponins showed moderate antiproliferative activity (ED₅₀ : 10-74μg/ml) against MK-1, HeLa and B16F10 cells.