A low degree of esterification pectic acid was obtained by sodium hydroxide treatment of apple pectin. Pectic acid was depolymerized with a commercially available pectinase and a mixture of oligo-GalA (DP2-8) was pooled together, the mixture was separated by a low-pressure anion-exchange resin column chromatography to obtain pure oligo-GalA. The degradation conditions were optimized as enzymatic reaction at 40 ℃ for 1 h, oligo-GalA monomers in the range of 2～5 with a purity degree over 92% analyzed by TLC and ESI-MS were prepared (yield of 37%). The results indicated that there also existed dimer molecular ion peaks along with oligogalacturonic acid monomer molecular ion peaks, and the presence of the dimer were identified by ESI-MS/MS.
徐溪, 李潇, 黄琳娟, 王仲孚. 苹果果胶活性寡聚半乳糖醛酸的分离制备及其ESI-MS分析研究[J]. 化学学报, 2010, 68(15): 1525-1531.
XU Xi, LI Xiao, HUANG Lin-Juan, WANG Zhong-Fu. Studies on Preparation of Oligogalacturonic Acids from Apple Pectin and Analysis by ESI-MS. Acta Chimica Sinica, 2010, 68(15): 1525-1531.