Interaction And Complex Compound Characteristics Of Iron And Anthocyanin Extracted From Black Bean Coats

Black bean,which is extensively cultivated in our country,is a traditional medicinal and edible agricultural products resource.In recent years,the development and utilization of natural harmless pigments is very popular in chemical plants and food science research filed.Black beans raw materials are readily available,inexpensive and suitable for the need of industrial production,which makes black bean anthocyanins has great application prospect in food,medicine and other fields.Anthocyanin extracted from black bean coats,which is a hydroxyl donor,is a good free radical scavenger and can chelate with metals to form anthocyanins-metal complexes.This could improve the stability of anthocyanin and contribute to the absorbing of metal elements,such as iron.In this issue,the interaction between anthocyanin extracted from black bean coats and iron ions[Fe(?)and Fe(?)]was investigated,providing a novel theory of multi-functional food that promotes the absorption of iron.By using the 60%acidic ethanol solution at pH 1.0,the anthocyanin was extracted from black bean coats under assist of ultrasonic.The content of anthocyanin determined by pH differential method was 6.915 mg/g,while the value was 6.965 mg/g by using the HPLC method.The interaction between black bean coats extracted anthocyanins and iron ions[Fe(?)and Fe(?)]was investigated in aqueous solutions at pH 1.0,3.0,5.0 and 7.3.The presence of iron ions changed the UV-Visible absorption spectra of anthocyanins for different degrees at experimental pH values,indicating the transformation of hydroxyl structure of anthocyanins.Fluorescence quenching spectra showed the complexes forming between anthocyanins and iron ions,and the quenching efficiency was increasing with the increasing of the iron ions concentration.Anthocyanins has the ability of protecting Fe(?)being oxidized and improving the solubility of Fe(?).The preparation type high performance liquid chromatography(HPLC)was applied to purify the anthocyanin extracted from black bean coats.98%purity was obtained and analyzed by high performance liquid chromatography(HPLC)and mass spectrum which identified the purity was cyanidin-3-glucoside.Using fluorescence spectroscopy and microscale thermodynamic instrument,the interaction mechanism between cyanidin-3-glucoside and iron ions[Fe(?)and Fe(?)]was investigated.Fluorescence spectrum results indicated the quenching of iron ions for C3G was static fluorescence quenching for that the values of Kq estimated in our study were all much more than 2.0×1010 per mol/s,the maximum dynamic quenching constant for various quenchers interacting with biopolymers.The combination of iron ions with C3G difference under different pH values that the binding constants and binding sites order were as follows:pH 1.0<pH 3.0<pH 5.0>pH 7.3 for C3G-Fe(?)complex,pH 1.0>pH 3.0>pH 5.0>pH 7.3 for C3G-Fe(?)complex.MST experiments show that the process of the chelating of C3G with iron ions was exothermic,spontaneously for ?G<0,?H<0,?S<0 and the Kd values,indicating the affinity,obtained was in accordance with fluorescence.At pH 1.0,3.0,5.0 and 7.3,C3G raised the Fe(?)stability by reducing the oxidation rate of Fe(?)by increasing the remaining percentage from 88.64%,62.45%,45.15%,40.31%to 94.11%,94.05%,94.18%,90.77%,respectively,during 10 days storage time and improved the solubility of Fe(?)from 90.01%,63.37%,49.46%,46.87%,34.64%and 4.84%to 94.30%79.24%,76.38%,67.06%,62.65%and 9.31%at pH 5.0,5.5,6.0,6.5,7.0,respectively.