高静压改善3,5-二咖啡酰奎宁酸与β-乳球蛋白复合物抗氧化活性的作用机制研究

China is rich in sweet potato leaves, with the annual production about 100 million tons. Sweet potato leaf polyphenols possess high antioxidant activity. However, as the phenolic hydroxyl group is too active, and unstable during processing and storing, the development and utilization of sweet potato leaf polyphenols are greatly restricted. In order to solve the above-mentioned problem, the present study proposed using high hydrostatic pressure (HHP) to improve the formation and antioxidant activity of polyphenol-protein compound, so as to improve the stability and antioxidant activity of sweet potato leaf polyphenols. In the preliminary study, it was found that the main component of sweet potato leaf polyphenols-3,5-dicaffeoylquinic acid (3,5-CQA) andβ-lactoglobulin (β-Lg) can form stable compound, and HHP treatment can improve the antioxidant activity of the above mentioned compound, but the internal mechanism of HHP treatment improving the antioxidant activity of the compound formed by 3,5-CQA and β-Lg is still not clear. In the present project, theories such as protein adsorption science and techniques such as high pressure fluorescence spectrum analysis will be used, and the effects of different HHP treatments on in vitro antioxidant activity, protein secondary structure, physicochemical properties, and combining power between 3,5-CQA and β-Lg of the compound formed by 3,5-CQA and β-Lg will be compared, so that the effect of HHP treatments on the formation of the compound will be clear, and the internal mechanism of HHP treatment improving the antioxidant activity of the compound formed by 3,5-CQA and β-Lg will be illuminated.

我国甘薯茎叶资源丰富，年产量约1亿吨。甘薯茎叶多酚具有较高的抗氧化活性，然而由于酚羟基极为活泼，加工贮藏过程中稳定性较差，限制了其开发利用。为解决上述问题，本研究拟利用高静压（HHP）处理，调控多酚与蛋白质复合物形成，从而提高甘薯茎叶多酚的稳定性与抗氧化活性。前期研究发现甘薯茎叶多酚中的主要成分3,5-二咖啡酰奎宁酸（3,5-CQA）与β-乳球蛋白（β-Lg）可形成复合物，且HHP处理可使复合物抗氧化活性显著提高，然而HHP处理改善复合物抗氧化活性的机制尚未明晰。本研究拟采用蛋白质吸附学等理论，结合高压荧光光谱分析等技术，通过考察不同HHP处理对3,5-CQA与β-Lg复合物抗氧化活性、蛋白二级结构、理化特性、3,5-CQA与β-Lg结合力等的影响，明确HHP处理对3,5-CQA与β-Lg复合物形成的影响规律，阐明HHP处理改善多酚-蛋白复合物抗氧化活性的机制。

我国甘薯茎叶资源丰富，年产量约1亿吨。甘薯茎叶多酚具有较高的抗氧化活性，然而由于酚羟基极为活泼，加工贮藏过程中稳定性较差，限制了其开发利用。为解决上述问题，本研究提出利用高静压（HHP）处理，调控多酚与蛋白质复合物形成，从而提高甘薯茎叶多酚的稳定性与抗氧化活性。前期研究发现甘薯茎叶多酚中的主要成分3,5-二咖啡酰奎宁酸（3,5-CQA）与β-乳球蛋白（β-Lg）可形成复合物，且HHP处理可使复合物抗氧化活性显著提高，然而HHP处理改善复合物抗氧化活性的机制尚未明晰。本研究通过考察不同HHP处理对3,5-CQA与β-Lg复合物抗氧化活性、蛋白二级结构、理化特性、3,5-CQA与β-Lg结合力等的影响，发现在pH值为7.0、35℃、NaCl溶液浓度为0、3,5-CQA与β-Lg摩尔比为5:1的条件下，制备的复合物抗氧化活性最强；随着高静压处理压力的升高，复合物抗氧化活性逐渐增强，在500 MPa（30min）时，复合物抗氧化活性最强。不同压力和加压时间对复合物理化特性存在显著影响，100 MPa加压30min可使复合物的溶解性由常压下的428.73 µg BSA/mL提高至760.96 µg BSA/mL，表面疏水性指数由常压下的253.51降至162.07，粒径由常压下的478.6 5nm降至267.20 nm。常压下3,5-CQA与β-Lg主要是通过疏水相互作用、静电相互作用和氢键形成非共价复合物；随着压力的升高，复合物的β-折叠含量逐渐减少，无规则卷曲含量逐渐增加；高静压处理增强了3,5-CQA酚羟基与β-Lg疏水腔的疏水氨基酸间的疏水相互作用，从而增强了复合物的稳定性。本项目成果可为HHP定向调控蛋白、多酚形成具有指定功能特性的复合物提供理论依据，为扩大甘薯茎叶多酚在食品、保健品及医药等领域的开发利用途径，缓解环境污染，提高甘薯加工产业附加值提供新的思路和方案。