Study On Preparation And Physicochemical Properties Of Proanthocyanidin Nanocomposites

Proanthocyanidin is a kind of natural polyphenol compound,which has strong antioxidant activity.It plays a unique advantage in anti-inflammatory,anti-tumor and anti-cancer fields.However,the low stability and bioavailability of proanthocyanidin have limited its practical application.In order to enhance the stability of proanthocyanidin and extend its biological activity,the nano carrier system was constructed by the synergistic assembly of polyphenols,proteins and polysaccharides.Therefore,casein and maltodextrin were selected in this study to construct proanthocyanidin nanocomposites and its preparation conditions were optimized.The changes of protein properties and the interaction between protein,polysaccharide and proanthocyanidin were explored.Furthermore,the storage stability,in vitro and in vivo antioxidant activity and simulated gastrointestinal digestion characteristics of the proanthocyanidin nanocomposites were systematically evaluated.The main conclusions were as follows:The graft of casein and maltodextrin was prepared by molecular self-assembly.The maximum grafting degree of casein-maltodextrin grafts was 57.91%.The browning index of grafts remained at about 0.25 and the grafts was controlled in the early stage of maillard reaction.Compared with casein,the solubility of grafts was significantly improved.The isoelectric point of casein was not changed by the grafting reaction,but the absolute value of?-potential of grafts was decreased.New functional groups were formed by self-assembly grafting,and the secondary structure of casein changed.The optimum conditions for the preparation of proanthocyanidin nanocomposites were obtained by orthogonal design.The mass ratio of proanthocyanidin to grafts was 2:5,the concentration of grafts was 2.5%(w/v),the pH of the solution was 7.0,the grafting reaction time was 15 h and the mass ratio of casein to maltodextrin was 1:2.The encapsulation efficiency of the nanocomposites was 93.48±0.20%,the average particle size was 158.69±1.70 nm and?-potential was-30.58±1.27 m V.Proanthocyanidin was embedded in the grafts without any chemical reaction.It was found that casein-maltodextrin proanthocyanidin nanocomposites had better stability during 28 days storage compared with casein proanthocyanidin nanocomposites obtained under the same preparation conditions.DPPH,ABTS and ORAC were used to investigate the antioxidant activity of proanthocyanidin nanocomposites.It was found that grafts can significantly reduce the loss of antioxidant activity of proanthocyanidin during storage and heat treatment.Proanthocyanidin nanocomposites can significantly prolong the life of C.elegans and decrease its accumulation of lipofuscin during the 16 days of culture.When treated with H₂O₂,the average life span of C.elegans cultured with proanthocyanidin nanocomposites was 31.11%longer than that of blank group,and its resistance to heat stress(35?)was also enhanced.There was a dose-dependent relationship between the activity of SOD and CAT and the concentration of proanthocyanidin nanocomposites.It was found that the nanocomposites could play a better sustained-release role in the simulated gastrointestinal digestion,and the release curve of nanocomposites in simulated gastric and intestinal fluids was in accordance with the zero-order kinetic release equation.