| In recent years,apples have become one of the most widely consumed fruits in China.The production of apple juice,jam and other products requires a large amount of apples,and the rise in apple production is bound to produce a large amount of apple pomace.Apple polyphenols are secondary metabolites of apples during the growth process,and are natural active substances extracted from apple pomace with antioxidant,anti-inflammatory and immunomodulatory properties.Traditional methods of extracting polyphenols from apple pomace are inefficient and prone to environmental pollution,which limits the utilization of polyphenols and thus causes a huge waste of resources.Starch nanoparticles(SNPs)have received widespread attention for their renewable,low-cost and biocompatible advantages.In this paper,SNPs of different particle sizes were prepared by ultrasonic-assisted chemical precipitation and adsorbed polyphenols from apple pomace polyphenol extracts to investigate the relationship between the particle size of SNPs and the amount of polyphenols adsorbed,on this basis,a kinetic model of adsorption of polyphenols was fitted and the anti-digestive capacity,antioxidant capacity and simulated in vitro release of polyphenols from starch nanoparticles(P-SNPs)adsorbed with polyphenols were evaluated,subsequently,In vitro cellular assays and mouse toxicology tests were performed to verify the safety of SNPs and PSNPs,finally,the effects of SNPs and P-SNPs on antioxidant activity and intestinal flora in mice were investigated.The results of the study are as follows:1.Five SNPs with different particle sizes were successfully prepared by ultrasonic-assisted chemical precipitation,and their adsorption of polyphenols from apple pomace extracts was further investigated.It was shown that the SNPs exhibited better adsorption performance and higher adsorption amount of polyphenols with decreasing particle size,and the kinetic fitting of the adsorption process revealed a better fitting of the proposed secondary kinetic model.2.The adsorption process of SNPs on polyphenols was optimized by orthogonal tests,and SNPs were finally prepared as adsorbent using starch solution with a concentration of 1%.PSNPs were produced by adsorption of polyphenols in fruit pomace solution at p H=5 and temperature of 30°C with 160 rpm oscillation frequency for 150 min,and the amount of polyphenols adsorbed was 4.65 μg/mg.Free polyphenols were treated with high temperature and UV light,and their DPPH radical scavenging activity was significantly reduced(P<0.05),however,when polyphenols were adsorbed on SNPs,the DPPH radical scavenging activity was well protected,indicating that SNPs have the ability to protect polyphenols against adverse factors in the environment;simulated in vitro digestion assay showed that the adsorbed polyphenols had good anti-digestion ability;during the simulated in vitro release of polyphenols The release of polyphenols by SNPs was slowed down when they were under harsh conditions such as gastric acid,while SNPs underwent continuous release of polyphenols until complete release when they were under intestinal conditions.3.The in vitro safety of SNPs and P-SNPs was demonstrated by cytotoxicity assays.The in vivo safety of SNPs and P-SNPs was evaluated by acute toxicity test and subchronic toxicity test in mice.The results of the acute test in mice showed that after 14 days of feeding,the body weight changes and diet of both male and female mice were within the normal fluctuation range,the morphology of the mice did not produce pathological changes,the hair color were normal,and no significant lesions were observed in internal organs after autopsy,and there were no significant differences in liver and kidney sections.In the subchronic toxicity test,compared with the control group,the mice in each dose group had good development,no abnormal lesions in liver and kidney sections,and the blood biochemical indexes and cytokines were within the normal range.4.The antioxidant activities of SNPs and P-SNPs and their effects on intestinal flora of mice were investigated.The results showed that SNPs and P-SNPs could increase the production of short-chain fatty acids,among which acetic acid and butyric acid were the highest,and propionic acid was lower than the two.In addition to acetic acid,the contents of propionic acid and butyric acid in PH group were higher than those in SH group.It was found that P-SNPs can promote the growth of beneficial bacteria,inhibit the growth of pathogenic bacteria,maintain intestinal homeostasis and promote the healthy development of mice intestinal flora.The in vivo antioxidant activities of SOD,MDA,GSH-PX,CAT and T-AOC were measured in serum,liver and kidney of mice in control and each dose group,and it was found that the in vivo antioxidant activities of mice infused with P-SNPs were higher than those of control and SNPs groups.The in vivo antioxidant activity of P-SNPs in the high dose group was higher than that of P-SNPs in the middle and low groups. |
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