Kai Zhu,Jinghua Wu,Ankai Hu,Zihao Yin,Zhiqiang Hou,Xingqian Ye,Shiguo Chen
A primary challenge of polysaccharide analysis is the need for comprehensive extraction and characterization methods. In this study, mulberry polysaccharides at different maturities were fully extracted through a two-step process involving ethylenediaminetetraacetic acid (EDTA) and sodium hydroxide (NaOH), and their structures were determined by a combination analysis of monosaccharides and glycosidic linkages based on liquid chromatography triple quadrupole mass spectrometry (LC/QqQ-MS). The results indicate mulberry polysaccharides mainly contain highly branched pectic polysaccharides, (1,3,6)-linked glucan, xylan, and xyloglucan, but the content of different portions varies at different maturity stages. HG decreases from 19.12 and 19.14% (green mulberry) to 9.80 and 6.08% (red mulberry) but increases to 17.83 and 11.83% as mulberry transitioned from red to black. In contrast, the contents of glucan showed opposite trends. When mulberry turns red to black, the RG-I arabinan chains decrease from 47.75 and 28.86% to 13.16 and 12.72%, while the galactan side chains increase from 1.18 and 1.91 to 8.3 and 6.49%, xylan and xyloglucan show an increase in content. Overall, the two-step extraction combined with LC/QqQ-MS provides a new strategy for extensive analysis of complex plant polysaccharides.
Protein glycation can produce the advanced glycation end products (AGEs), which has a potential health risk due to its relevance with diabetic complications. Searching for potent inhibitors to suppress hyperglycemia-induced protein glycation is of great significance. Here, we probed the anti-glycation potential of epicatechin gallate (ECG), an important ingredient of green tea, by spectroscopy and chromatography supplemented by molecular docking. It was found that ECG suppressed the carbonylation and the formation of amyloid cross-β structures of bovine serum albumin (BSA) as well as the generation of AGEs in BSA–fructose model by 65.6%, 73.7% and 87.0%, resepctively. A combination of ECG with epigallocatechin gallate (EGCG) at molar ratios from 0.5:1 to 2:1 exhibited the interactive effects on AGEs formation from moderate antagonism to synergy. Moreover, ECG at 44.2 μg/mL showed a trapping efficiency of 81.6% for the important precursor methylglyoxal (MGO) of AGEs within 24 h, and the formed ECG–mono-MGO and ECG–di-MGO adducts were verified by LC–QqQ–MS analysis. The inhibitory effect of ECG on the protein glycation may be due to its MGO trapping and the specific binding with certain amino acid residues of BSA. These findings may provide the theoretical basis for the development of ECG as an inhibitor of protein glycation.
The presence of potential carcinogen 4(5)-Methylimidazole (4-MeI) in foods causes much concern, stressing the need of a sensitive determination means. Here, we proposed a high-sensitivity method to determine 4-MeI in biscuits using dansyl chloride derivatization and disperse liquid-liquid micro-extraction (DLLME) followed by a liquid chromatography-ion trap mass spectrometry (LC-IT-MS) analysis. This developed method was subsequently compared to the solid phase extraction combining with liquid chromatography-triple quadrupole mass spectrometry (SPE-LC-QqQ-MS) method. The optimized derivatization conditions were 30 °C and 10 min. Results suggested that the column retention time (RT) was significantly extended, and the MS signal response of 4-MeI-dansyl derivative was also amplified. The developed DLLME-LC-IT-MS method in 4-MeI determination provided satisfactory linearity in a range of 0.5–300 ng/mL (R 2 > 0.9991), inter-day accuracy (87-102%) and precision (%RSD ≤ 13.6%) with the quantification limit of 0.2 ng/mL, which obtained similar results comparing to the conventional SPE-LC-QqQ-MS method.
危险品化学品经营许可证（带存储）