柚皮素7-O-葡萄糖苷非对映异构体的NMR波谱分析

二氢黄酮糖苷化后产生的R与S构型非对映异构体在¹H NMR谱上会呈现一些差别，但文献对其差别描述非常有限.为便于利用¹H NMR谱图判断二氢黄酮糖苷的R与S构型非对映异构体，本文首先在植物药皂荚提取物中分离得到一种二氢黄酮苷-柚皮素7-O-葡萄糖苷R与S构型混合物，分析其氘代二甲亚砜（DMSO-d₆）溶液的¹H NMR、¹³C NMR、¹H-¹H COSY、¹H-¹³C HSQC和¹H-¹³C HMBC谱，对其¹H和¹³C NMR谱峰进行了归属；然后，采用手性色谱柱对该混合物进行分离，结合圆二色光谱（CD）技术确定构型；最后，为鉴别R与S构型柚皮素7-O-葡萄糖苷在¹H NMR谱中特征差别谱峰，避免葡萄糖残基质子对二氢黄酮苷元质子化学位移的影响，采集了R与S构型柚皮素7-O-葡萄糖苷及其混合物氘代乙腈（CD₃CN）溶液的NMR谱，结果显示葡萄糖残基端基质子H-1″化学位移差别最为明显，为9.4 Hz；5-位酚羟基质子化学位移差别为5.8 Hz，C环上3个质子化学位移差也较明显．

NMR Characterization of Flavanone Naringenin 7-O-Glycoside Diastereomer

To discriminate R and S flavanone glycoside using NMR, the mixture of R and S naringenin 7-O-glycoside was first isolated from Gleditsia sinensis. 1H and 13C NMR data of the mixture were recorded with 1H NMR, 13C NMR, 1H-1H COSY, 1H-13C HSQC and 1H-13C HMBC in DMSO-d6 solution. The two diastereomers were then separated with chiral chromatographic isolation, with their absolute configurations determined by circular dichroism. To avoid the disturbance of protons from glucose residues to dihydroflavonoid, 1H NMR spectra were acquired for pure R and S naringenin 7-O-glycoside and their mixture in CD3CN. The two diastereomers showed the largest proton chemical shift differences at the end group of glucose residue (H-1″) with a chemical shift difference of 9.4 Hz. The OH-5 proton showed a chemical shift difference of 5.8 Hz. The chemical shift of the three protons on ring C were all influenced by configuration.