龙眼果肉干制过程中的多糖-蛋白质相互作用及其消化吸收影响的机制研究

There are experimental evidences indicating the formation of polysaccharide-protein complex (PPC) in longan pulp during hot-air drying. The potential mechanism of intermolecular interaction between polysaccharide and protein and its impact on the nutritional quality of pulp are unclear. This project firstly aims to investigate the dynamic polysaccharide-protein interaction in longan pulp with different drying methods, analyze the physicochemical differences among PPCs formed at the different stages of drying, and then establish the multidimensional standard fingerprints of typical PPCs by chemometrics methods. Various fractions of polysaccharide and protein from fresh longan pulp will be isolated and purified. The interaction between each of their fractions will be investigated using the wet-heating model system. The structures of PPCs generated by the reaction system will be elucidated for exploring the mechanism of intermolecular interaction. Meanwhile, the fingerprints of these PPCs will be compared with the standard ones to indicate the mechanism related to the formation of PPCs during longan pulp drying. The typical fraction of polysaccharide and protein, as well as PPC, will be chosen and comparatively evaluated on the features of gastrointestinal digestion, gut microbial degradation and intestinal absorption by in vitro simulated methods. This project focuses on the intermolecular interaction between polysaccharide and protein occurred under complicated process conditions and the structure-effect relationship related to its impact on the digestion and absorption of polysaccharide and protein, to provide scientific evidences for the drying technology innovation and nutritional regulation of bulk/special agricultural products.

龙眼果肉热风干制过程伴随多糖-蛋白质复合物的形成，但其潜在机制与营养品质影响均不清楚。探析不同干制方式下龙眼果肉中多糖和蛋白质的相互作用规律，分析不同干制阶段所获复合物的理化特征差异，基于化学计量学构建标志性复合物的多维标准指纹图谱。分离纯化鲜肉中多糖和蛋白质的不同级分，构建湿热体系探析其级分之间的相互作用，结合产物结构解析揭示分子间作用机制，并依据指纹图谱相似性指证果肉干制时的复合物生成机理。筛选多糖和蛋白质的代表性级分与复合物，体外模拟分析三者的消化、酵解和吸收特征差异。研究复杂加工体系中的多糖-蛋白质相互作用与消化吸收影响的构效机制，可为大宗/特色农产品干制技术创新与营养品质调控提供依据。

多糖是龙眼果肉中的重要营养功能因子，在果肉热干燥后发生显著的构效变化，但其潜在的分子机制尚不清楚。本项目考察果肉不同干制方式对多糖理化性质、体外活性和消化特性的影响，基于美拉德反应探析潜在分子机制及构效关系，并评价多糖的肠道保护作用。.（1）从新鲜以及热风、真空、红外和冷冻干制的果肉中分别提取粗多糖(即FLP、HDLP、VDLP、IDLP和FDLP)，其化学组成、官能团特征和分子量分布明显不同。FDLP具有较强的DPPH自由基和羟自由基清除能力，而HDLP刺激巨噬细胞NO和TNF-α生成的活性更强。粗多糖在模拟肠液体系中相对稳定，但经模拟唾液和胃液消化后发生一定程度降解，释放出以葡萄糖为主的少量还原糖，而IDLP的消解表现特异。.（2）分离制备新鲜果肉杂多糖级分（LP）和蛋白级分，考察LP与蛋白级分和氨基酸在不同条件下的美拉德反应特征，并选取赖氨酸制备复合物MLP。LP和MLP的化学组成存在显著差异，反应导致LP的260nm紫外吸收和酰胺区红外谱带明显增加，并主要消耗α-型糖苷键。LP为球状颗粒，>100 kDa级分占6.0%。而MLP呈交联的链状，>100 kDa级分占45.0%。同一浓度下，MLP的自由基清除能力及巨噬细胞刺激活性明显高于LP，但对HepG2和SGC7901肿瘤细胞的生长抑制作用较弱。.（3）LP能显著改善环磷酰胺诱导的小鼠肠道上皮细胞损伤，增加绒毛长度及其与隐窝深度之比，并促进Muc2、ZO-1、claudin-1/4和E-cadherin的mRNA与蛋白的表达。LP经过肠道微生物部分酵解后产生乙酸和丙酸，促进微生物的生长。LP亚级分LPI、LPII、LPIII和LPIV的化学组成存在显著差异，重均分子量分别为147.0、159.3、19.4和44.0 kDa。各亚级分主要含→3)-α-Araf-(1→、→3,6)-β-Galp-(1→、α-Araf-(1→、→5)-α-Araf-(1→、→3)-β-GalpA-(1→和/或α-Rhap-(l→，对Caco-2细胞模型的ZO-1、Occludin、claudin-1、E-cadherin的mRNA表达影响不同，其中LPI和LPII具有相对较高的刺激活性。.研究明晰干制工艺对龙眼果肉多糖的影响，为果肉干品质提升提供思路；探析多糖与氨基酸的美拉德反应特征及复合产物的构效变化，揭示果肉的组分相互作用。