Effect of Glycosylation on the Physicochemical Properties,Structure and Iron Bioavailability of Ferritin Extracted from Tegillarca granosa

Iron deficiency anemia(IDA)is a major global health problem.Tegillarca granosa has been considered as an excellent source of iron given its high content of iron-binding protein,ferritin.The aim of the present study was to determine the physicochemical properties,protein structures,and iron uptake of ferritin extracted from T.granosa,and to evaluate the potential impacts of chitosan glycosylation on these characteristics.Based on Box-Behnken design and response surface methodology,the optimal conditions for glycosylation included a ferritin/chitosan mass ratio of 4:1,a pH of 5.5,a reaction time of 10 min,and a reaction temperature of 50℃.Glycosylation caused decreased surface hydrophobicity and elevated water-holding capacity of ferritin due to the introduction of hydrophilic groups.Additionally,glycosylation improved antioxidant capacity of ferritin by 20.69%–189.66%,likely owing to the protons donated by saccharide moiety to terminate free radical chain reaction.The in vitro digestibility of ferritin was elevated by 22.56%–104.85%after glycosylation,which could be associated with lessβ-sheet content in secondary structure that made the glycosylated protein less resistant to enzymatic digestion.The results of the iron bioavailability in Caco-2 cells revealed that ferritin(78.85–231.77 ngmg^(−1))exhibited better iron bioavailability than FeSO4(51.48–114.37 ngmg^(−1))and the values were further elevated by glycosylation with chitosan(296.23–358.20 ngmg^(−1)),which may be related to the physicochemical properties of ferritin via glycosylation modification.These results provide a basis for the development of T.granosa derived ferritin and its glycosylated products,and can promote the utilization of aquatic resources.

Assessment of Iron Bioavailability in Ten Kinds of Chinese Wheat Flours Using an in vitro Digestion/Caco-2 cell Model

Abstract Objective To compare iron bioavailability （Fe BV） from ten selected kinds of Chinese wheat flours in order to provide scientific basis for further human trials and enable plant breeding programs to screen biofortified wheat cultivars. Methods An in vitro digestion/Caco-2 cell model was used to assess Fe BV of ten flour samples from six leading Chinese wheat cultivars and the stability of Fe BV in one cultivar was studied across three growing environments. Results Significant differences were observed in both Fe BV and Fe bioavailability per gram of food （Fe BVPG） among cultivars （P〈0.01） grown at the same location with the same flour extraction rate. Zhongyou 9507 and Jingdong 8 had Fe BV 37%-54% and Fe BVP（3 103%-154% higher than the reference control. In the Anyang environment, Zhongyou 9507 had a higher wheat flour-Fe level and Fe BVPG. Differences in Fe BV were detected in cultivars with different flour extraction rates. Conclusion Zhongyou 9507 and Jingdong 8 were identified as the most promising cultivars for further evaluation of efficacy by using human subjects. The growing environments had no effect on Fe BV, but did have a significant effect on Fe BVPG. Fe bioavailabilities in low-extraction （40%） flours were higher than those in high-extraction （78%） flours.

Phytate:impact on environment and human nutrition.A challenge for molecular breeding

Phytic acid (PA) is the primary storage compound of phosphorus in seeds accounting for up to 80% of the total seed phosphorus and contributing as much as 1.5% to the seed dry weight. The negatively charged phosphate in PA strongly binds to metallic cations of Ca, Fe, K, Mg, Mn and Zn making them insoluble and thus unavailable as nutritional factors. Phytate mainly accumulates in protein storage vacuoles as globoids, predominantly located in the aleurone layer (wheat, barley and rice) or in the embryo (maize). During germination, phytate is hydrolysed by endogenous phytase(s) and other phosphatases to release phosphate, inositol and micronutrients to support the emerging seedling. PA and its derivatives are also implicated in RNA export, DNA repair, signalling, endocytosis and cell vesicular trafficking. Our recent studies on purification of phytate globoids, their mineral composition and dephytinization by wheat phytase will be discussed. Biochemical data for purified and characterized phytases isolated from more than 23 plant species are presented, the dephosphorylation pathways of phytic acid by different classes of phytases are compared, and the application of phytase in food and feed is discussed.

Comparison of bioavailability and transporters gene expression of four iron fortificants added to infant cereals

Iron deficiency is one of the most important nutritional disorders around the world. To reduce this health problem in infants, most countries have developed different iron fortification programs as a long-term strategy. However, it is necessary to select the best iron source to get the highest bioavailability with the lowest impact on the organoleptic properties of the foods. The aim of this research was to assess the in vitro bioavailability and intestinal cellular transport of four iron sources (electrolytic iron: EI, ferrous fumarate: FF, a micronized and dispersible ferric pyrophosphate: MDFP, and ferrous sulphate heptahydrated: FSH) used to fortify infant cereals. Fortified cereals were in vitro digested and soluble fractions were then incubated in Caco-2 cells to study iron retention, transport and uptake. Moreover, mRNA expression of iron transporters and ferritin formation were also measured in cells incubated with the iron standard salts. Iron solubility, uptake percentage, transport and uptake efficiencies by the Caco-2 cells were significantly higher in cereals fortified with FSH than with EI, obtaining intermediate values for the other two iron fortificants. MDFP induced higher expression of iron transporters Zip-14 and HEPH than other iron sources. FSH promoted the highest iron storage protein ferritin, followed by FF and MDFP, while EI presented the lowest in vitro bioavailability due to its low solubility. This work demonstrated that iron absorption, storage, and gene expression of transporters depend on the source of iron. These are important challenges to be taken into consideration when assessing the potential of iron fortificants.