基于多孔石墨化碳柱-四极杆-飞行时间质谱解析甜菜果胶精细结构

采用高温酸法提取甜菜果胶(SBP), 经强阴离子交换柱层析分离, 获得甜菜果胶水洗脱组分(SBPW)和盐洗脱组分(SBP3). 单糖组成分析和分子量表征结果表明, SBPW主要由半乳糖(Gal)、 阿拉伯糖(Ara)和半乳糖醛酸(GalA)组成, 分子量为1100； SBP3则以GalA为主, 分子量为41450. 通过顺序酶法降解, 应用多孔石墨化碳柱-四极杆-飞行时间质谱(PGC-Triple-Tof MS)联用技术分析鉴定了SBPW和SBP3寡糖的精细结构. 结果表明, SPBW的主链为→4)-α-GalA-(1→2)-α-Rha-(1→]重复单元构成的Ⅰ型聚鼠李半乳糖醛酸(RG-Ⅰ果胶), 鼠李糖O-4位被中性糖侧链α-(1→5)阿拉伯聚糖和β-(1→4)半乳聚糖]所取代. SBP3由α-1,4链接的聚半乳糖醛酸(HG)和RG-Ⅰ构成, HG和RG-Ⅰ通过α-1,4糖苷键直接相连, 并发现了α-GalA(1→2)α-Rha(1→4)α-Rha(1→4)α-GalA(1→2)α-Rha的新特征结构.

Combined PGC-Triple-Tof-MS Enables the Separation， Identification of Sugar Beet Pectin Derived Oligomers

Sugar beet pectin（SBP） was extracted by high-temperature acid method， the water-eluted components（SBPW） and salt-eluted components（SBP3） were obtained by strong anion exchange chromatography. The results of monosaccharide composition and molecular weight analysis showed that SBPW was mainly composed of galactose（Gal）， arabinose（Ara） and galacturonic acid（GalA）， with a molecular weight of 1100， while SBP3 was dominated by GalA and weighted 41450. Combined sequential enzymatic degradation and porous graphitized carbon column-quadrupole-time-of-flight mass spectrometry（PGC-Triple-Tof MS）， the fine structure of SPPW and SPP3 oligosaccharides was analyzed. The results showed that the main chain of SPBW was ［→4）-α-GalA-（1→2）-α-Rha-（1→］ repetitive units composed of RG-Ⅰ pectin， and neutral sugar side chain ［α-（1→5） arabinan and β-（1→4） galactan］ were substituted for Rha at the O-4 position. SBP3 consisted of HG and RGⅠ with a molar of 3：2， HG was a linear structure of α-1，4-linked GalA， HG and RG-Ⅰ domains were connected directly by α-1，4 glycoside bonds. New characteristic structures of oligosaccharide have also been found， similar to α-GalA（1→2）α-Rha（1→4）α-Rha（1→4）α-GalA（1→2）α-Rha.