Study On Astaxanthin-protein Self-assembly Mediated By Fatty Acids And Its Complex Absorption Properties

Astaxanthin(ASTA)is a non-vitamin A-derived ketone fat-soluble carotenoid,which has many biological activities,such as anti-oxidation,enhancement of body immunity,anti-tumor,anti-diabetes,anti-obesity,prevention of cardiovascular diseases,etc.However,the poor water solubility,stability and oral absorption rate of ASTA limit its application in food industries.Protein is an important carrier system for the delivery of bioactive substances,which can effectively improve the water-solubility and stability of carotenoids,but the effect of promoting absorption needs to be further improved.This is because dietary lipids are essential for the absorption of carotenoids.The related studies and previous studies of our research group have shown that dietary fatty acid(FAs)can bind to protein in the form of ligands,which has potential application value in efficient delivery of fat-soluble nutrients such as carotenoids.However,there are differences in the absorption-promoting effects of different FAs on carotenoids.Therefore,in this study,seven kinds of common FAs were selected as protein lipid ligands and self-assembled with bovine serum albumin(BSA)by p H-driven method to form FA-BSA complexes,which was used as ASTA carrier to study and analyze the effects on water dispersibility,storage stability,absorption effect and in vivo antioxidant activity of ASTA.The main results are as follows:1.Study on the preparation and storage stability of ASTA-FA-BSA complexes.Based on the p H-driven method,seven kinds of FA-BSA monodisperse systems with relatively uniform distribution can be obtained under the optimum preparation conditions(BSA 5.0 mg/m L and BSA/SFA molar ratio 1:4).Then using these FA-BSA systems as the carriers of ASTA,it was found that all the ASTA-FA-BSA complexes formed could present a relatively clear and transparent state in aqueous solution,and the intervention of lauric acid(LAA),palmitic acid(PA),stearic acid(SA),oleic acid(OA),linoleic acid(LA),arachidonic acid(AA)and docosahexaenoic acid(DHA)increased the encapsulation efficiency of ASTA by BSA from about 90% to about 95%.Stored in the dark at 4 ? and 25 ? for 35 days,it was found that the degradation process of the ASTA-FA-BSA complexes conformed to the first-order reaction kinetic equation.Compared with free ASTA,the half-life of ASTA embedded in LAA-BSA,PA-BSA,SA-BSA,OA-BSA,LA-BSA,AA-BSA and DHA-BSA complex at 4 ? increased by10.07,10.97,11.83,8.64,7.18,7.87 and 1.68 times,respectively.These results indicated that FA-BSA complexes could improve the storage stability of ASTA,and the enhancement ability of saturated FA-BSA complexes was positively correlated with its carbon chain length,which was higher than that of unsaturated FA-BSA complexes.2.Study on the interaction between ASTA and FA-BSA complexes.The interaction mechanism between ASTA and FA-BSA complexes was investigated through multispectral technique and molecular docking method,and compared with that of ASTA and BSA.The results showed that ASTA had a strong fluorescence quenching effect on both FA-BSA complexes and BSA,and the quenching process was static quenching.ASTA interacted with FA-BSA complexes and BSA spontaneously mainly through hydrogen bonds and van der Waals forces,and their interaction had little effect on the microenvironment surrounding protein tyrosine and tryptophan residues.Based on the results of site competition experiments and molecular docking,the main binding sites of ASTA on FA-BSA complexes and BSA were site ?and site ?,respectively.In summary,the intervention of FA did not change the fluorescence quenching mode and the main binding force between ASTA and BSA,but it changed the main binding site of ASTA on BSA from site ? to site I.3.Study on the absorption effect and in vivo antioxidant activity of ASTA-FA-BSA complexes.Compared to ASTA distributed directly in the water,after simulated digestion in vitro,the bioavailability of ASTA embedded with BSA,LAA-BSA,PA-BSA,SA-BSA,OA-BSA,LA-BSA,AA-BSA and DHA-BSA complexes was increased by 18.25,22.77,25.67,27.33,29.88,28.47,29.01 and 12.78 times,respectively,and after intestinal absorption in mice,the serum response value was increased by 71.87%,88.80%,100.29%,123.28%,139.89%,119.13%,149.79% and 60.36%,respectively.The results of in vivo and in vitro absorption experiments were basically the same.Among them,SA-BSA,OA-BSA and AA-BSA complex had stronger ability to promote the absorption effect of ASTA,and their serum response value could reach 80.53%,86.52% and 90.09% of the pure oil delivery system,respectively.After administering three different doses of ASTA-SA/OA/AA-BSA complexes to mice for 14 consecutive days,it was found compared with free ASTA and ASTA-BSA complex,the accumulation of ASTA-SA/OA/AA-BSA complex in serum,liver and eye tissues of mice increased significantly in a concentration-dependent manner,and the order was ASTA-AA-BSA >ASTA-OA-BSA > ASTA-SA-BSA.In addition,the total antioxidant capacity,total superoxide dismutase activity,glutathione peroxidase activity and catalase activity of ASTA-AA-BSA complex in serum,liver and eye tissues of mice were also concentration-dependent,which were higher than those of free ASTA and ASTA-BSA complex.