天門冬去子果實之甾體皂苷研究

Abstract

先前的研究顯示百合科植物蘆筍(Asparagus officinalis)的種子具有抗癌活性的甾體皂苷，因此我們想去探討同屬植物但尚無研究報告的常見庭園植物天門冬(A. densiflorus)是否具有相似的抗癌活性成分。 將去子之果實以水萃取，繼之以極性分割為乙酸乙酯層、丁醇層及水層。而丁醇層，經由離心式分配層析儀及Sephadex LH-20進行劃割得到富含甾體皂苷的部份，再以半製備高效液相層析管柱RP-18分離(MeOH-H2O, ACN-H2O)而得五個甾体皂苷，包括26-O-β-D-glucopyranosyl-22α-methoxy-(25S)-furostan-3β,26-diol 3-O-α-L-rhamopyranosyl-(1→4)-β-D-glucopyranoside (1), 26-O-β-D-glucopyranosyl-22α-methoxy-(25R)-furostan-3β,26-diol 3-O-α-L-rhamopyranosyl-(1→4)- β-D-glucopyranoside (2), 26-O-β-D-glucopyranosyl-22α-hydroxy-(25R)-furostan-3β,26-diol 3-O-[α-L-rhamnopyranosyl-(1→2)- α-L-rhamopyranosyl-(1→4)]- β-D-glucopyranoside} (3), (25R,S)-5β-spirost-5-en-3β-ol 3-O-α-L-rhamnopyranosyl-(1→4)- β-D-glucopyranoside (4), (25S)-5β-spirostan-3-ol 3-O -α-L-rhamnopyranosyl-(1→2)- α-L-rhamnopyranosyl-(1→4)- β-D-glucopyranoside (5) 這些成分之結構皆經光譜分析確認，其中化合物1、3為首次分離的之天然物。而化合物5具有抗乳癌細胞(MCF-7)活性，IC50為5.19 μg/ml。

Recent studies indicated that the seed of Asparagus officinalis (Liliaceae) contained cytotoxic steroidal glycosides. Hence, we wanted to explore whether a related and uninvestigated species, A. densiflorus, a common garden plant, contained similar bioactive constituents. The water extract of the fresh fruits void of seeds was divided into fractions soluble in EtOAC, n-BuOH and H2O. The n-BuOH soluble part was further fractionated over centrifugal partition chromatography (CPC), and Sephadex LH-20 to give fractions rich in glycosides. Separation of these fractions via semipreparative RP-18 HPLC column (MeOH-H2O, ACN-H2O) led to the isolation of five glycosides. They are characterized as 26-O-β-D-glucopyranosyl-22α-methoxy-(25S)-furostan-3β,26-diol 3-O-α-L-rhamopyranosyl-(1→4)-β-D-glucopyranoside (1), 26-O-β-D-glucopyranosyl-22α-methoxy-(25R)-furostan-3β,26-diol 3-O-α-L-rhamopyranosyl-(1→4)- β-D-glucopyranoside (2), 26-O-β-D-glucopyranosyl-22α-hydroxy-(25R)-furostan-3β,26-diol 3-O-[α-L-rhamnopyranosyl-(1→2)- α-L-rhamopyranosyl-(1→4)]- β-D-glucopyranoside} (3), (25R,S)-5β-spirost-5-en-3β-ol 3-O-α-L-rhamnopyranosyl-(1→4)- β-D-glucopyranoside (4), (25S)-5β-spirostan-3-ol 3-O -α-L-rhamnopyranosyl-(1→2)- α-L-rhamnopyranosyl-(1→4)- β-D-glucopyranoside (5)Their structures were elucidated mainly by NMR spectral analysis. This study leads to the isolation and characterization of two new furostanoid glycosides(1, 3). In addition, compound 5 is demonstrated to possess cytotoxicity against breast cancer cell line (MCF-7) with IC50 value of 5.19 μg/ml。