光谱学与光谱分析, 2018, 38 (8): 2386, 网络出版: 2018-08-26  

黑米花色苷酰化修饰红外光谱分析

Analysis of Acylation Modification of Black Rice Anthocyanins Using Fourier Transform Infrared Spectroscopy (FTIR)
作者单位
1 东北农业大学食品学院, 黑龙江 哈尔滨 150030
2 黑龙江省农业科学院大豆研究所, 黑龙江 哈尔滨 150086
摘要
黑米花色苷易受外部环境影响发生降解致使局部分子结构破坏而使营养价值和保健功能有所下降。 利用有机酸提供酰基对黑米花色苷进行修饰来提高花色苷结构的稳定性。 利用红外光谱分析经咖啡酸酰化修饰黑米花色苷的结构变化。 结果表明: 黑米花色苷酰化修饰前后于官能团区3 650~3 200和1 680~1 620 cm-1处均有吸收峰, 且其于指纹区1 282.68和1 277.51 cm-1处出现酚羟基吸收峰, 于1 056.07和1 054.03 cm-1处出现醇羟基吸收峰, 719.90和719.71 cm-1处出现苯环上C—H面外弯曲振动吸收峰。 由此可见, 黑米花色苷酰化修饰后主要结构框架仍为花色苷的芳环结构。 此外, 黑米花色苷酰化修饰前后于1 900~1 650 cm-1间1 714.28和1 728.13 cm-1处均出现共轭羰基的特征吸收峰, 对应于可直接连接在苯环上的α-羰基结构, 由此说明黑米花色苷结构中存在着酰基基团。 黑米花色苷经酰化修饰后红外图谱于1 517.20 cm-1处出现新吸收峰, 其正好处于1 800~900 cm-1双键(不含氢)伸缩振动区, 指纹区876.65 cm-1处亦出现了苯环上的C—H面外弯曲振动吸收峰。 与之相呼应在经二阶导数处理后红外光谱图中在2 500~2 000 cm-1间出现了新的波动, 此波段为累积双键伸缩振动区, 而官能团区3 650~3 200 cm-1间3 370.20 cm-1处的吸收峰正好处于多分子缔合区。 由此可见, 在咖啡酸作为酰基供体, 酰化修饰黑米花色苷时由于分子间的重新缔合于结构中引入了新的酰基基团而呈现出一种双酰化的空间结构。 黑米花色苷酰化结构中有机酸与糖链相连, 将有机酸置于2-苯基苯并吡喃骨架的表面, 这种堆积作用模式可以较好地抵抗水的亲核攻击和其他降解反应进而提高黑米花色苷结构的稳定性。
Abstract
The black rice anthocyanins are vulnerable to degradation due to the external environment, resulting in the destruction of local molecular structure, which reduces the nutritional value and health function. The stability of anthocyanin structure was improved by modifying anthocyanins with acyl groups provided by organic acids. The structural changes of anthocyanins modified by caffeic acid acylation were analyzed with Fourier transform infrared spectroscopy (FTIR). The results showed that the absorption peaks of functional group in 3 650~3 200 and 1 680~1 620 cm-1 were the same between both before and after anthocyanins modified, the phenolic hydroxyl absorption peak appeared in the fingerprint area of 1 282.68, 1 277.51 cm-1, and the alcoholic hydroxyl absorption peak appeared at 1 056.07, 1 054.03 cm-1, the absorption peak of C—H surface bending vibration in benzene ring appeared at 719.90 and 719.71 cm-1. It can be seen that the major structural framework of acylated black rice anthocyanins is still the aromatic ring structure of anthocyanins. In addition, the characteristic absorption peaks of conjugated carbonyl all appeared at 1 714.28 and 1 728.13 cm-1 in the area of 1 900~1 450 cm-1 both before and after the modification of anthocyanins, which corresponded to α-carbonyl structure in benzene ring, thus indicating the presence of acyl groups in the structure of the black rice anthocyanins. The new absorption peaks of modified anthocyanin appeared at 1 517.20 cm-1 in the infrared spectrum, which is right located in the stretching vibration zone of 1 800~900 cm-1 double bond (no hydrogen), the absorption peak of C—H surface bending vibration in benzene ring appeared at 876.65 cm-1 in the fingerprint region. At the same time, new fluctuations were observed at 2 500~2 000 cm-1 in the infrared spectrum after the second derivative treatment, which is the cumulative double bond stretching vibration region. The absorption peak of functional group at 3 370.20 cm-1 between 3 650~3 200 cm-1 is located in the multimolecular association region. It can be seen that when caffeic acid is used as acyl donor, the acylated modified black rice anthocyanins present a double acylated spatial structure due to the re-association of the molecules with the introduction of new acyl groups in the structure. The organic acid was linked to the sugar chain in the structure of black rice anthocyanin, and it was placed on the surface of 2-phenyl benzo pyran skeleton. This stacking model can resist water nucleophilic attack and other degradation reactions, which can improve the stability of black rice anthocyanin structure.

谢凤英, 李凤凤, 张爽, 毕伟伟, 张秀玲, 张晓南. 黑米花色苷酰化修饰红外光谱分析[J]. 光谱学与光谱分析, 2018, 38(8): 2386. XIE Feng-ying, LI Feng-feng, ZHANG Shuang, BI Wei-wei, ZHANG Xiu-ling, ZHANG Xiao-nan. Analysis of Acylation Modification of Black Rice Anthocyanins Using Fourier Transform Infrared Spectroscopy (FTIR)[J]. Spectroscopy and Spectral Analysis, 2018, 38(8): 2386.

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