分子结构与食品基质对虾青素酯稳定性及生物利用度的影响机制

Natural astaxanthin is a powerful antioxidant and it can penetrate the blood- brain barrier, which contributes significantly to its role in improving human health. However, the diversiform applications of astaxanthin in food industry are restricted by two key factors: the low storage stability and the low bioavailability. The traditional strategies to solve these problems are mainly based on the stabilization technology, which in turn leads to an insufficient study of the relationships between structures and functions of these molecules. . Astaxanthin esters are the main molecular forms of astaxanthins in nature. The auto-oxidation in vitro, transmembrane transport in a digestion simulative model – Caco-2 cells are intended to be researched. Moreover, we are supposed to make insight into the absorption and metabolism of astaxanthin esters in ICR mouse model as well as simulating the molecular docking to pancreatic lipase. The project is aimed at elaborating the effects of molecular structures on the stability and bioavailability, together with demonstrating the molecular mechanisms of the transmembrane transport of astaxanthin isomers. Meanwhile, the influencing mechanisms of food constituent properties on stability and bioavailability will to be revealed in combination probing the food matrix effects. . This project is expected to break the limitation in choosing molecular forms of astaxanthins as functional factors and to provide a scientific evidence for designation and development of highly bioavailable and steady-state excipient foods. In short, this research will certainly make sense in the area that astaxanthin esters are processed and utilized in a high-value way. Besides, the research is meaningful to explore a scientific dietary intake strategy for astaxanthin esters.

天然虾青素具有强大的抗氧化和穿透血脑屏障的特性，对改善人体健康具有重要意义。而低加工贮藏稳定性和低生物利用度是其在食品中多元化应用的关键限制因素。传统解决策略以分子外的稳态化技术为主，但缺乏对分子结构-性质关系的系统探讨。本项目拟以自然界中的主要存在形态—酯化态虾青素分子为目标物，通过研究其在体外自氧化、模拟消化—Caco-2细胞跨膜转运和模型小鼠体内吸收代谢的过程，并结合基于胰脂肪酶分子对接模拟手段，阐明分子结构对虾青素酯稳定性和生物利用度的影响机制以及虾青素跨膜转运的分子机理；同时结合食品基质效应，进一步揭示食品体系组成特性对虾青素酯稳定性和生物利用度的影响机制。本项目研究可突破人们对虾青素功能因子分子形态选择的局限性，为高生物利用度虾青素稳态化赋型食品的设计和开发提供新的科学依据，对于虾青素资源的高值化转化和利用，及其营养膳食新策略的探寻具有重要意义。

建立了虾青素结构和纯度分析的HPLC-DAD-(APCI)-MS/MS方法。以雨生红球藻藻油（虾青素含量10%）为原料，经酶法制得高纯度游离虾青素（F-Asta）。采用DMAP和EDCI催化，成功合成了不同脂肪酸链长、饱和度、酯化程度的虾青素单酯（Asta-ME）和虾青素双酯（Asta-DE），经硅胶柱层析纯化得到14种不同结构高纯度虾青素酯（Asta-E）。采用Autodock软件对不同分子结构Asta-E与胰脂肪酶分子进行体外模拟对接，发现Asta-ME更易结合且碳链越长结合能力越弱，其中Asta-C4:0结合最佳。表明脂肪酸链越长、饱和度越高、酯化程度越高，热稳定性越好。通过测定DPPH自由基清除率发现，脂肪酸含双键越多Asta-E抗氧化性越强。建立了虾青素氧化产物测定的HPLC-(APCI)-MS/MS方法。研究小鼠体内的代谢动力学和生物利用度，考察消化道不同部位的消化吸收情况，表明Asta-E在小肠内被水解成F-Asta被生物体利用。.攻克了脂质载体、多层乳液、微胶囊稳态化运载体系构建的关键技术。考察了多种蛋白、多糖基质，表明乳清蛋白和褐藻糖胶壁材包封具有较好稳定性，乳清蛋白对Asta-E消化吸收效果的促进作用最强，壳聚糖包封的Asta-E微胶囊生物利用度最高。研究Asta-E与β-乳球蛋白（β-Lg）、羟丙基-β-环糊精（HP-CD）食品基质之间相互作用的动力学，阐明了它们的结合能力、位点及方式，表明Asta-ME亲和力强，长链脂肪酸Asta-E优于短链的，不饱和脂肪酸Asta-E优于饱和的，虾青素DHA单酯（Asta-C22:6）结合能力最强。Asta-E与β-Lg为静态猝灭机制，单一结合位点，主要为疏水作用和静电排斥；推测Asta-E进入HP-CD疏水腔，通过氢键结合，脂肪酸链对复合物的稳定性有重要影响。在筛选出的食品基质基础上，开发了虾青素DHA单酯酸奶新营养配方食品。微胶囊包埋掩蔽了虾青素的不良气味，最大程度上保留了酸奶的原有风味。.项目实施，不仅对虾青素酯稳定性和生物利用度的影响因素、规律及机制的揭示具有重要的理论意义，同时为筛选高稳定性和高生物利用度的虾青素酯分子形式，以及为高生物利用度虾青素酯稳态化赋型食品的设计提供依据和应用前景，进而为虾青素酯资源的高值化转化和利用，及其科学营养膳食探寻新的策略和方案。