黄酮化合物与Fe(Ⅱ)络合反应的动力学研究

Study on Reaction Kinetics between Flavonoids and Fe(Ⅱ)

目的:以光谱动力学力法建立评价黄酮化合物与Fe(Ⅱ)络合反应能力的方法。方法:采用紫外-可见分光光度法研究了20℃时9种黄酮化合物在乙醇溶液中与Fe(Ⅱ)发生络合反应的光谱变化。结果:除几茶素和白杨素在该条件下不能与Fe(Ⅱ)络合反应,其他7种黄酮化合物均能络合Fe(Ⅱ),其形成的络合物的光谱吸收带较游离黄酮化合物发生了红移,且其络合反应符合零级反应的特征,速率常数大小依次为:杨梅素>槲皮素>黄芩素>山奈酚>黄芩苷>芦丁>木犀草素。结论:黄酮化合物的B环上具有邻三酚羟基(3′,4′,5′-OH)与Fe(Ⅱ)络合能力较强,邻二酚羟其(3′,4′-OH)次之,单个酚羟基(4′-OH)较弱。黄酮苷元成苷后,由于糖基体积较大,产生空间位阻效应而导致黄酮苷络合能力下降。该方法简单易操作,可用于评价黄酮化合物络合Fe(Ⅱ)反应的能力。

Objective： To establish a method of evaluating reaction abilities of flavonolds with Fe（Ⅱ） with 9 flavonoids have been investigated in ethanol solution at 20 ℃ by UV-Visible spectroscopy.Result： Based on the changes of the UV-Vis spectra,we could determine that 7 flavonoids（quercetin,myricetin,rutin,kaempferol,baicalin.baicalein and luteolin） occurred complesx reaction,due to the bathochromic shift of the wavelength band.On the other hand.no bathochromic shift as indication for complexation of catechin and chrysin could be observed under the conditions we had chosen.The kinetics of complex formation were investigated with the ligand in zero-order by the presence of Fe（Ⅱ）.The reation rate constants in turn were as follows： myricetin quercetin baicalein kaempferol baicalin rutin luteolin.Conclusion： The strongest chelating power is the pyrogallol hydroxyl in ring B,and the pyrocatechol hydroxyl ranks second,a single phenolic hydroxyl relatively weak.When flavonoid aglycones transform into glycosides.their complex capacity will decrease significantly.The system investigated can be considered as a simplified method to evaluate the complex ability between flavonoids and Fe（Ⅱ）.