The Research On Bioactivities Of Vegetable Condensed Tannins And Preserve On Fresh-cut Apples

Acanthus ilicifolius Linn(Acanthaceae)and Kandelia candel,two mangrove plants,are most widely distributed in Fujian Province.The rich chemical properties give them a variety of biological activities.However,there are few studies on the vegetable tannins from A.ilicifolius and Kandelia candel.Vegetable tannin is a protective substance produced by carbohydrate metabolism during the evolution of plants.It is mainly found in leaf,root,skin,shell and pulp of plant body and it has become a research hotspot in many fields such as cosmetics,health care products and food.In this research,we have isolated tannins from A.ilicifolius leaves and Kandelia candel fruit,studied on the structure,antioxidant activity,antityrosinase activity and antibacterial activity.After comprehensive consideration,we have determined to use the tannins from A.ilicifolius leaves for the determination of practical efficacy:the preservation effect of fresh cut apple.The study aims to to provide theoretical foundation of exploitation and efficient utilization of the tannins.After isolated and puried tannins from A.ilicifolius leaves and Kandelia candel fruit,we have analysised their total phenolics(TP)content and extractable(ECT)content.The TP and ECT of tannins from A.ilicifolius leaves are measured to be 88.09±2.3 mg GAE/g DW and 34.3±2.24 mg/g DW.The TP and ECT of tannins from Kandelia candel fruit are measured to be 176.26 ± 1.5 mg GAE/g DW and 29.1±1.30 mg/g DW.We have investigated the structure of the two tannins with three methods:HPLC、13C NMR and MALDI-TOF-MS.From the result,we knew that the polymer chain lengths of tannins from A.ilicifolius leaves were found to be 3-mers to 14-mers,and the main components of the structural unit include catechin/epicatechin,galatechin/epicatechin,and a small amount of amphicin/epigalin.The ion peaks of tannins from Kandelia candel fruit are periodically distributed,the polymer chain lengths were found to be 2-mers to 20-mers,and the ion peak of the 6-mers is the highest.The main structural units include amphicin/epigalin and catechins/epicatechin,and a small amount of galactin/epicatechin.Several measures were used to determine the antioxidant activity of the tannins can react antioxidant capacity comprehensively.There,we have used DPPH、ABTS and FRAP to analysis the antioxidant activity of the two tannins.From the results,the DPPH clearance rate,ABTS clearance rate and FRAP antioxidant value of the two tannins were higher than that of vitamin C equivalent under the same conditions,shows that tannins from A.ilicifolius leaves and Kandelia candel fruit both have high antioxidant capacity.Then we have studied the inhibitory mechanism of the two tannins on o-diphenolase activity of tyrosinase.We found as the concentration of tannin increased,the inhibitory effect was more obvious.The values of IC50 were 19.7±0.13 p,g/mL and 6.42 ± 0.348 μg/mL,and inhibition type analyses displayed the two tannins are mixed type inhibitors and reversible of the enzyme.In addition,the fluorescence spectra showed that the two tannins can in combination with tyrosinase,and that would reduce the fluorescence intensity of the enzyme.Meanwhile,we measured the antibacterial effects of the two tannins on Escherichia Coil,Bacillus subtilis,Salmonella typhimurium,P.Aeruginosa and Staphyloccocus aureus.The results showed that the inhibiting effect of tannins from A.ilicifolius leaves on Salmonella typhimurium was almost no,and it had inhibitory effect on other bacteria.The inhibiting effect of tannins from Kandelia candel fruit on Escherichia Coil was almost no,but it had inhibitory effect on other bacteria.Morever,the antibacterial effect of the two tannins showed dose effect.Finally,after consideration of cost,sample acquisition,economic value and other reasons,we choose tannins from A.ilicifolius leaves as the research object.After process the fresh apples with different concentration tannins,we found compared to the blank control,the vitamin C content of processed apples can be maintained at a high level and the weight loss rate is small.When the tannins concentration was lmg/mL,the inhibition of browning was the best,and the ppo activity remained low.It shows that tannins from A.ilicifolius leaves can slow the respiration of fresh cut apples,reduce the consumption of apple’s nutrients and increase the storage life of apples.In summary,a more comprehensive understanding of the structure and physiological and biochemical activity of tannins from A.ilicifolius leaves and Kandelia candel fruit provides a theoretical basis for the further research,development and utilization of the two tannins.