Background: Inositol hexaphosphate (IP 6 ) is a well-known inhibitor of iron absorption, whereas the effects of the less-phosphorylated derivatives of IP 6 are less known. Objectives: The objective was to investigate the effects of inositol tri-, tetra-, and pentaphosphates (IP 3 , IP 4 , and IP 5 , respectively) on iron absorption in humans. Design: Iron absorption was measured in 5 experiments from single meals by extrinsic labeling with 55 Fe and 59 Fe and determination of whole-body retention and the erythrocyte uptake of isotopes. In experiments 1-3 the meals contained white-wheat rolls to which 10 mg P as IP 5 , IP 4 , or IP 3 , respectively, was added. Inositol 1,2,6-triphosphate [Ins(1,2,6)P 3 ] and a mixture of isomers of IP 4 and IP 5 were studied. White-wheat rolls contained 10 mg P as IP 3 + IP 4 and 2 mg P as IP 5 + IP 6 in experiment 4 and 20 mg P as IP 3 + IP 4 and 3 mg P as IP 5 + IP 6 in experiment 5; inositol phosphates were obtained via fermentation of sodium phytate. Each experiment had 8-11 subjects. Results: In experiment 1, iron absorption was reduced by 39%, whereas there was no significant effect on iron absorption in experiments 2 and 3. In experiments 4 and 5, iron absorption was reduced by 54% and 64%, respectively, suggesting that IP 3 and IP 4 contributed to the inhibitory effect. Conclusions: IP 5 has an inhibitory effect on iron absorption, whereas IP 3 and IP 4 in isolated form have no such effect. IP 3 and IP 4 in processed food contribute to the negative effect on iron absorption, presumably by binding iron between different inositol phosphates. To improve iron absorption from cereals and legumes, degradation of inositol phosphates needs to be to lessphosphorylated inositol phosphates than IP 3 .Am J Clin Nutr 1999;70:240-6.

The effects of inositol tri-, tetra-, penta-, and hexaphosphates on iron solubility were studied in vitro. Pure inositol phosphates (0.125-10 wmol) were added to lg of freeze-dried wheat roll and digestion was performed simulating physiological conditions. Soluble iron was used as an index of iron bioavailability.The pure inositol phosphate fractions were prepared by hydrolysis of sodium phytate and separation on anion exchange resin. The inositol phosphates were identified and quantified by HPLC. Addition of 10 pmol inositol hexa-and pentaphosphate reduced iron solubility from 39% (reference) to 0.2% and 6%, respectively, while the same amount of inositol tetra-and triphosphate slightly increased the iron solubility.Thus, degradation of inositol hexa-and pentaphosphates seemed to significantly reduce the inhibiting effect on iron availability.

A sensitive high-performance ion chromatography (HPIC) method for separation and quantitative determination of inositol mono- to hexaphosphate (IP1−IP6) isomers in selected foods and intestinal contents is described. The method includes extraction of samples with HCl, separation of the inositol phosphates from the crude extract by anion-exchange chromatography, separation on high-performance ion-exchange columns with gradient elution in two combined HPIC systems, and detection using either postcolumn reaction and UV detection (system 1) or chemically suppressed conductivity detection (system 2). IP2−IP6 in samples were determined on the first system, which also separated isomers of IP4 and IP5. Fractions of IP1−IP3 from the first system were transferred to the second system after some additional sample preparation and analyzed for isomers. The applicability and sensitivity of the method are illustrated by measuring the content of inositol phosphates in foods, ileal contents, and feces of human balances. Keywords: Inositol phosphate isomers; high-performance ion chromatography; HPIC; food; intestinal content

The demand for vegetable proteins increases globally and seaweeds are considered novel and promising protein sources. However, the tough polysaccharide-rich cell walls and the abundance of polyphenols reduce the extractability and digestibility of seaweed proteins. Therefore, food grade, scalable, and environmentally friendly protein extraction techniques are required. To date, little work has been carried out on developing such methods taking into consideration the structural differences between seaweed species. In this work, three different protein extraction methods were applied to three Swedish seaweeds (Porphyra umbilicalis, Ulva lactuca, and Saccharina latissima). These methods included (I) a traditional method using sonication in water and subsequent ammonium sulfate-induced protein precipitation, (II) the pH-shift protein extraction method using alkaline protein solubilization followed by isoelectric precipitation, and (III) the accelerated solvent extraction (ASE®) method where proteins are extracted after pre-removal of lipids and phlorotannins. The highest protein yields were achieved using the pH-shift method applied to P. umbilicalis (22.6 ± 7.3%) and S. latissima (25.1 ± 0.9%). The traditional method resulted in the greatest protein yield when applied to U. lactuca (19.6 ± 0.8%). However, the protein concentration in the produced extracts was highest for all three species using the pH-shift method (71.0 ± 3.7%, 51.2 ± 2.1%, and 40.7 ± 0.5% for P. umbilicalis, U. lactuca, and S. latissima, respectively). In addition, the pH-shift method was found to concentrate the fatty acids in U. lactuca and S. latissima by 2.2 and 1.6 times, respectively. The pH-shift method can therefore be considered a promising strategy for producing seaweed protein ingredients for use in food and feed.

Fast and simple analytical methods for the determination of inositol bis- to hexakisphosphates or only inositol hexakisphosphate in foods and feces are presented. The methods are both faster and simpler with regard to analytical detection and sample pretreatment as compared to previously reported methods. The samples are pretreated using extraction and centrifugal ultrafiltration and analyzed using high-performance ion chromatography (HPIC) with gradient or isocratic elution. The analytes are detected using ultraviolet detection after postcolumn reaction. The methods are efficient, highly selective, and appropriate for analyzing inositol phosphates in food and feces samples. The between- and within-day variances were generally below 8 and 5% (relative standard deviation), respectively, for the presented HPIC method with gradient elution.