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The study of the influence of Mg(ii) and Ca(ii) ions on caffeic acid autoxidation in weakly alkaline aqueous solution using MCR-ALS analysis of spectrophotometric data†
New Journal of Chemistry ( IF 3.3 ) Pub Date : 2018-03-19 00:00:00 , DOI: 10.1039/c8nj00871j
Slavoljub C. Živanović 1, 2, 3, 4, 5 , Aleksandar M. Veselinović 2, 3, 4, 5, 6 , Žarko J. Mitić 2, 3, 4, 5, 6 , Goran M. Nikolić 2, 3, 4, 5, 6
Affiliation  

UV-Visible spectrophotometry was used to study the influence of Mg(II) and Ca(II) ions on caffeic acid (CA) autoxidation in weakly alkaline aqueous solution. While the autoxidation rate was very slow in the absence of metal ions, both Mg(II) and Ca(II) ions greatly enhanced the autoxidation rate. Determination of the spectral and concentration profiles of the individual components involved in the CA autoxidation processes in the presence of metal ions was performed using multivariate curve resolution-alternating least squares (MCR-ALS) analysis of spectrophotometric data. MCR-ALS analysis supported by the quantum chemical calculations of electronic absorption spectra for possible initial reaction products showed that CA autoxidation in the presence of Mg(II) and Ca(II) ions proceeds by the instant formation of CA–metal complexes followed by the almost simultaneous formation of CA quinone anions and various CA dimers and the final transformation into polymeric, humic acid-like, products. Also, the MCR-ALS analysis revealed that the effect of Mg(II) ions was more pronounced at the initial stage of autoxidation. The differences in the influence of Mg(II) and Ca(II) ions on the CA autoxidation may be attributed to the stronger metal ion–ligand interaction for Mg(II) ions caused by their larger ionic potential in comparison to Ca(II) ions. The results of this study may be important for better understanding of the interactions of Mg(II) and Ca(II) ions with natural phenolic food antioxidants and thus significant for understanding their activities in real systems and optimization of conditions for the processing and/or storage of certain types of foods.

中文翻译:

使用分光光度法数据的MCR-ALS分析 研究Mg(ii)和Ca(ii)离子对弱碱性水溶液中咖啡酸自氧化的影响

紫外可见分光光度法用于研究Mg(II)和Ca(II)离子对弱碱性水溶液中咖啡酸(CA)自氧化的影响。尽管在没有金属离子的情况下自氧化速度非常慢,但Mg(II)和Ca(II离子大大提高了自氧化率。使用分光光度数据的多元曲线分辨率-交替最小二乘法(MCR-ALS)分析,确定在金属离子存在下,CA自动氧化过程中涉及的各个组分的光谱和浓度分布。通过电子吸收光谱的量子化学计算对可能的初始反应产物进行的MCR-ALS分析表明,在Mg(II)和Ca(II)离子是通过立即形成CA-金属络合物而形成的,然后几乎同时形成CA醌阴离子和各种CA二聚体,最后转化为类似腐殖酸的聚合产物。此外,MCR-ALS分析表明,Mg(II)离子的作用在自动氧化的初始阶段更为明显。Mg(II)和Ca(II)离子对CA自氧化的影响之所以不同,可能是由于与Ca(II)相比,它们的离子势较大,导致Mg(II)离子具有更强的金属离子-配体相互作用。离子。这项研究的结果可能对于更好地了解Mg(II)和Ca(II)具有天然酚类食品抗氧化剂的离子,因此对于理解其在实际系统中的活性以及优化某些类型食品的加工和/或储存条件具有重要意义。
更新日期:2018-03-19
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