Study On Bioavailability Of Tea Fl Uorine In Caco-2 Cells

Tea tree(Camellia sinensis(L.)O.Kuntze)is a kind of fluorine-enriched plants.The content of fluorine in tea is affected by many factors such as cultivars and growth environment of tea plants.Fluorine is an essential trace element of the human being.Small amount of intake could effectively prevent dental caries while excessive intake is not good for human body.There are many forms of fluorine in nature,they also have different effects on the human body due to their different bioavailability.In this thesis,same fresh leaves were processed into green tea,black tea and dark tea respectively.In order to evaluate fluorine bioavailability and explore possible transport ways,Caco-2 cells as the model were used to study the uptake of tea water extracts fluorine and polysaccharide fluorine.The results of the experiments will be shown as follows:1.Chemical components and fluoride content of different kinds of teaThe contents of water extract in green tea was higher than black tea and dark tea.Green tea had the highest content of polyphenols and catechins,and the contents in dark tea and black tea were lower.Additionally,black tea had higher contents of theaflavin and soluble sugar.The fluorine content was in the order of dark tea>black tea>green tea,which indicated that different processing techniques had different degrees of influence on the chemical components and fluorine content of tea.2.Effects of different tea components and fluoride on the proliferation activity of Caco-2cellsThere were differences in the components and fluorine content of tea extracts in the same fresh leaves because of their different processing techniques.The rank of the content of polyphenols and catechins was:green tea water extract>black tea water extract>dark tea extract.The rank of the fluorine content was:dark tea water extract>black tea water extract>green tea extract.The content of theaflavins and soluble sugar in the aqueous extract of black tea was relatively high.In dark tea rough polysaccharides,the contents of polyphenols,uronic acid,neutral sugar and protein were all higher than those of green tea polysaccharides and black tea polysaccharides.The fluorine content showed the opposite result.The same rule existed for the component change of dialysis polysaccharides and rough polysaccharides.Compared with fluorine of tea dialysis polysaccharides and rough polysaccharides,it suggested that fluorine and rough polysaccharides existed as small non-tightly bonded molecules.Different tea extracts have different effects on Caco-2 cell viability owing to their different components.Corresponding fluorine concentration of each extract is lower than that of Na F corresponding to fluorine IC₅₀ value.This illustrated that the fluoride content of the extracts was not the major factor in reducing cell viability.It was probably because polyphenols and other substances exerted influence on cell viability.3 Absorption and uptake of different types of fluorine in Caco-2 cellsFluoride absorption and uptake varies among different types of tea,absorption and uptake were dependent on time and concentration.Comparing the fluorine absorption of different type of tea water extracts,the result showed that the fluorine absorption of green tea water extract and Na F had the highest proportion,the fluorine absorption of the black tea water extract was the second,and the dark tea water extract was the lowest(p<0.05).Comparing the fluorine absorption of different rough polysaccharide,the fluorine absorption of green tea rough polysaccharide was higher than that of black tea rough polysaccharide and dark tea rough polysaccharide(p<0.05)in low fluorine concentration.When the concentration of fluorine was 1.2?g/m L,the fluorine absorption of black tea rough polysaccharide was higher than that of green tea rough polysaccharide fluorine and dark tea rough polysaccharide(p<0.05).The fluorine absorption capacity of dialysis polysaccharides also varied among different tea.The fluorine absorption capacity of black tea dialysis polysaccharides was higher than that of green tea dialysis polysaccharides and dark tea dialysis polysaccharides(p<0.05).Comparing fluorine in water extracts,fluorine in rough polysaccharide,fluorine in dialysis polysaccharide and Na F,the result showed that absorption of fluorine in water extract and Na F was higher,that of rough polysaccharide was in second place,and that of dialysis polysaccharide was the lowest(p<0.05).The apparent permeability coefficient of the fluorine of tea extract is more than 10^-6cm/s,it suggested that all the fluorine of tea extract had great bioavailability.4.Mechanism of absorption and transport of different types of fluorine in Caco-2 cellsThe Caco-2 cell model was used to study the uptake of fluoride AP-BL side and BL-AP at different time and concentrations.The results showed that positive absorption and uptake of fluoride were positively correlated with the concentration and time,and the ratio of two-way transmission P_ratio<1.5,P_app>10^-6cm/s,which indicated that the fluorine of tea had good bioavailability and the passive transport was the main absorption way.