| 1. BackgroundWorld Health Organization (WHO) reports that more than200million people suffer from iron deficiency in developing countries. Thesurvey ofChinese NationalNutritionand Health in2002showed that the average of anemia rate was20.1%. The anemia induced by iron deficiency has beinga universal public health problem.The bioavailability is the mineral utilized of normal body by the proportion of total mineral, and therefore, the bioavailability is the key to investigate mineral absorption.The factors affecting iron bioavailability include that Chemical states of iron, biological factor of body, the mechanism of iron absorption, transporter and dietary factor.Firstly, we will investigate that dietary factor which caused reduction, such as Vitamin C, cysteine impact on iron valence in this part, and we will research the iron absorption in Caco-2cells under corresponding conditions.At the same time, we also study other dietary factors which caused complexation such as lysine, histidine, cysteine, phytate, and tartaric acid impact on the complexation of iron status.2. MethodsFirstly, the study will improve and establish a viable iron valence analysis method. Secondly, analysis the food components impact on the valence of iron status and complex situations taking use of the method and reference method established prior, under simulated physiological conditions. Finally, it will analysis the different dietary factors impact on the absorption rate Fe (Ⅱ) or Fe (Ⅲ) using of Caco-2cell model. By contacting the chemical structure of dietary factors and dose-response relationship to investigate the causes and mechanisms which dietary factors affect iron absorption.2.1The improved analytical methods of Phenanthroline iron valence.(1) Determine the absorption wavelength.(2)Set up a Control group without light, color rendering and measuringabsorbance separately.(3)Whether has Interference to Fe (Ⅱ) Determination by comparing ammonium chloride, EDTA,NTA three metals masking agent.(4) The effect of masking agent-NTA on the accuracy of Fe (Ⅱ) measurement.(5)Compare the accuracy of two methods for total iron:reduction and dual-wavelength spectrophotometric determination2.2Discuss the affect of dietary factors to iron state under simulating physiological conditions.(1) Simulate physiological conditions in vitro.(2) Survey the chelating ability of dietary factors on iron.(3) Survey the reduction ability of dietary factors on iron.2.3The research of food ingredient impact on the bioavailability of iron and Mechanism.(1) Establish Caco-2cells model and do absorption experiments.(2) Adopt acid digestion combined with ICP-AES to evaluate the iron content.3. Results and conclusion3.1The improved analytical methods of Phenanthroline iron valence. Adopting masking agent could solve the problem of photochemical reactions, and the suitable masking agent of Fe (Ⅲ) is the NTA. The direct spectrophotometric method of chromogenic agent has a narrow range, when the Fe (Ⅲ) content in the total iron≥52%, the relative error is larger, but when the Fe (Ⅲ) content in the total iron≤90%, NTA masking method can be used. Taking use of two control charts and95%confidence interval graph could certificate that reduction method is more accurate.3.2Discuss the affect of dietary factors to iron state under simulated physiological conditionsin vitro.(1) With ascorbic acid/cysteine and Fe (Ⅲ) molar ratio increases, the reduction rate is increasing under simulated physiological conditionsin vitro.(2) Different organic acids have different complexation capacities on Fe (Ⅱ) under the same molar ratio; with oxalic acid/phytic acid and Fe (Ⅱ) molar ratio increases, its Fe (Ⅱ) complexation rate increased, under the different molar ratio of the same organic acid type.(3) Different amino acids have different complexation capacities on Fe (Ⅱ) under the same molar ratio; with cysteine/methionine/lysine/leucine/tryptophan/valine/isoleucine/histidine and Fe (Ⅱ) molar ratio increases, its Fe (Ⅱ) complexation rate increased,under the different molar ratio of the same Amino acids type.3.3The research of food ingredient impact on the bioavailability of iron and mechanism.(1) The absorption rate of Fe (Ⅱ) was significantly higher than the control group of Fe (III). This proves that the mechanisms which Fe (Ⅱ) enter intestinal epithelial cells through DMT land NRAMP2exist. Meanwhile, except the group of1:1molar ratio,the reduction rate and the absorption rate has highly correlated, indicating that the reduction of ascorbic acid play a great role in promoting iron absorption process.(2) Tartaric acid has promoting effect on Fe (Ⅱ) absorption. The effect of Tartaric acid on Fe (Ⅱ) absorption has significantly positive correlation with complexation rate. Phytic acid has maximum inhibition on iron absorption. When their molar ratio is10:1, and there was no significant increased in the inhibition as soon as they exceed this value. The affect of oxalic Acid on Fe (Ⅱ) absorption is complex:1) When the Fe (Ⅱ)/oxalic acid molar ratio>1:5, the oxalic acid showed inhibition;2) When the Fe (Ⅱ)/oxalic acid molar ratio equal to1:10, the oxalic acid showed catalytic role;3) When the Fe (Ⅱ)/oxalic acid molar ratio≤1:50, the role of oxalic acid is not obvious.(3) Cysteine play a significant role in promoting of Fe (Ⅲ) and Fe (Ⅱ) absorption, the reduction rate of Fe (Ⅲ) has a strong positive correlation with the absorption rate. The reduction effect to Fe (III) is the key factor to affect its absorption.(4) These amino acidswill be divided into three groups in this study. It willanalysis the influence mechanism combined with supply/electron-withdrawing effect of these amino acids and corresponding chemical structure. |
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