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本文主要研究了配位色谱法分离齐墩果烷型和乌苏烷型五环三萜同分异构体的分离机理。基于计算模拟分析,β-环糊精(β-CD)和其衍生物为适宜的配位剂。采用HPLC法测定了包合物的表观形成常数,并制备了asiaticoside-B与β-CD包合物。实验结果显示:流动相中添加葡萄糖基-β-环糊精(Glu-β-CD)时,同分异构体的分离度为11.95,比添加β-CD或添加甲基-β-环糊精(DM-β-CD)时(分别为9.61和9.89)都略高些。假定五环三萜类化合物与β-CD形成1∶1的包合物,对于asiaticoside-B,流动相中添加Glu-β-CD时,表观形成常数(K F)为2 534 L/mol,比添加β-CD或添加DM-β-CD时(分别为1 467和1 373 L/mol)都略大些。根据asiaticoside-B与β-CD包合物的红外光谱解析及计算模拟,推测asiaticoside-B的E环上甲基部分进入了β-CD的空腔内,而其羰基基团没有进入β-CD的空腔内,其糖苷部分与亲水性的β-CD空腔外部形成氢键作用力。因此,配位色谱法分离齐墩果烷型和乌苏烷型五环三萜同分异构体的分离机理可以推测如下:齐墩果烷型和乌苏烷型五环三萜同分异构体E环上甲基的不同空间位阻导致了同分异构体的不同色谱分离行为。
In this paper, the separation mechanism of the separation of oleanane and pentasodium triterpenoid isomers by coordination chromatography was studied. Based on computational modeling, β-cyclodextrin (β-CD) and its derivatives are suitable complexing agents. The apparent formation constants of the inclusion complexes were determined by HPLC. Asiaticoside-B and β-CD inclusion complexes were prepared. The experimental results showed that the resolution of isomers was 11.95 when glucose-β-cyclodextrin (Glu-β-CD) was added to the mobile phase compared with β-CD or methyl-β-cyclodextrin Fine (DM-β-CD) (9.61 and 9.89, respectively) were slightly higher. Assuming that the pentacyclic triterpenoids and β-CD form a 1: 1 inclusion complex, for asiaticoside-B, the apparent formation constant (KF) of Glu-β-CD at the mobile phase is 2 534 L / Slightly larger than when β-CD was added or when DM-β-CD was added (1 467 and 1 373 L / mol, respectively). According to the IR spectra analysis and calculation of asiaticoside-B and β-CD inclusion complexes, it is speculated that the methyl moiety on the E ring of asiaticoside-B enters the β-CD cavity and the carbonyl group does not enter β-CD Of the cavity, the glycosidic part of the hydrophilic β-CD cavity outside the formation of hydrogen bonding force. Therefore, the separation mechanism of the separation of oleanane type and pentasil triterpenoid isomers by the complexation chromatography can be presumed as follows: Oleanane type and pentasil type pentacyclic triterpenes are the same Different steric hindrance of methyl groups on the E ring of the structure leads to different chromatographic separation behavior of the isomers.