| As a natural polyphenol compound,anthocyanin is an important functional active ingredient in purple sweet potato.It has anti-inflammatory,anti-cancer,anti-oxidant and anti-aging effects.With the increasing demand for healthy foods,developing fermented products rich in anthocyanins and adding them as pigments to fermented products has become a new trend in the future.At present,there are few studies on the effect of strains on purple sweet potato anthocyanins.In this experiment,purple sweet potato anthocyanins were used as the research object,and the content,composition,antioxidant activity,and stability of purple sweet potato anthocyanins before and after fermentation of the strain were analyzed.In addition,using Caenorhabditis elegans as an animal model,the anti-aging effects of purple sweet potato anthocyanins before and after fermentation and their possible mechanisms were studied,providing theoretical references for the development of fermented products rich in anthocyanins.The main findings are as follows:(1)Ultrasound-assisted ethanol solution was used to extract anthocyanins from Yuzixiang 11,and the AB-8 macroporous resin was used for purification.Using antioxidant activity as an indicator,the strain that can effectively improve the antioxidant activity of anthocyanins was screened and identified as Weissella confusa.Through single factor experiments,it was determined that the suitable fermentation conditions were 37?,2%strain inoculation rate,and initial fermentation pH 6.3.After adding anthocyanin,the strain can reach the maximum growth 10 h earlier,and the maximum growth was increased by 14.4%.(2)The results of ultraviolet-visible spectroscopy analysis showed that the anthocyanin solutions before and after fermentation showed three characteristic absorption peaks around 250-300 nm,300-330 nm,and 500-520 nm.The anthocyanin after fermentation treatment The maximum absorption wavelength appears red shift.UPLC-QTOF-MS technology was used to discover three anthocyanin substances in the anthocyanin extract,which are caffeic acid,7-hydroxycoumarin,trans-Cinnamic acid,peonidin 3,5-diglucoside,peonidin 3-glucoside,kaempferol-7-O-glucoside,feruloyl quinic acids,cyanidin 3-glucoside,1,5-dicaffeoylquinic acid,chlorogenic acid.(3)In the 24h fermentation process,the DPPH·clearance ability,·OH clearance ability,ABTS~+·clearance ability of anthocyanins can be increased by 4.2%,11.2%,and7.4%,respectively;the anthocyanin fermentation broth can be treated with light for 4 d.Shows good light stability,especially strong stability at 4°C,and almost no degradation occurs within 5 days of treatment;anthocyanins after fermentation show higher pH stability,but with increasing pH,the stability of anthocyanins gradually decreases;anthocyanins show strong stability in gastric juice,but are extremely unstable in intestinal juice,and the stability of anthocyanins in the intestinal juice after fermentation was reduced.(4)The anthocyanins before and after fermentation can extend the life of the nematodes and increase the survival rate of the nematodes under stress.They had no negative impact on their reproductive capacity,but had a certain impact on their growth and development.Anthocyanins before and after fermentation can reduce the levels of MDA,ROS,and lipofuscin in the nematodes,and the fermented anthocyanins had a more significant effect than untreated anthocyanins at the 5th day of age.(5)Through the analysis of the anti-aging-related gene expression levels in the nematodes,it was found that in the fermentation broth group of nematodes,the gene expression levels of daf-2 and akt-1 were down-regulated by 43%and 63.4%,respectively,compared with the blank group.The gene expression of sir-2.1,skn-1,hsp-16.2,and sod-3 showed a significant up-regulation trend compared with the blank group.In the control group of nematodes,the expression of jnk-1 gene was significantly down-regulated by 70%,and sir-2.1,skn-1,and sod-3 showed a significant up-regulation trend compared with the blank group. |
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