Inositol hexaphosphate phytic

FIGURE 10,42 Structures of components of the calcium signaling pathway Inositol hexaphosphate (phytic acid) appears not to be synthesized by mammalian cells. The phytic acid in the diet can, to some extent, be hydrolyzed to give inositol. Inositol is required in the diet of rodents but not of humans. 

Inositol (hexahydroxycyclohexane) occurs in several isomeric forms. Myo-inositol (or meso-inositol) is an important constituent of phospholipids and is the only isomer with biological activity. Inositol hexaphosphate (phytic acid) is found in avian erythrocytes, where it binds to hemoglobin, thereby regulating the oxygen capacity of the blood. It is also important as an intracellular messenger in a number of pathways. 

Synenyms Hexakis (dihydrogen phosphate) myo-inositol Inositol hexaphosphate myo-lnositol, hexakis (dihydrogen phosphate) myo-inositol hexakisphosphate myo-inositol hexaphosphate Phytic acid (INCI)... 

Plant foods contain relatively large amounts of inositol phosphates, including the hexaphosphate, phytic acid. Phytate chelates minerals, such as calcium, zinc, and magnesium, forming insoluble complexes that are not absorbed. However, both intestinal phosphatases and endogenous phosphatases (phytase) in many foods dephosphorylate a significant proportion of dietary phytate. The inositol released can be absorbed and utilized for phosphatidylinositol synthesis. 

Phosphate is better used when supplied by food than when supplied by phosphate salts, such as potassium phosphate. The food phosphate occurs largely as phosphate esters and, with gradual hydrolysis, enters the body relatively slowly and is used efficiently in the metabolic processes. Phosphate supplied as inorganic phosphate is rapidly absorbed, with a tendency to be excreted in the urine rather than to be used by tissues (Schuette and Linkswilcr, 1962). The phosphate in bran occurs largely in the form of phytic acid (inositol hexaphosphate). The phosphate groups of fhis compound may be only partially hydrolyzed in the gut- Phytic acid tends to be excreted via the fecal route as a complex with iron or calcium. 

Phytic acid is inositol hexaphosphate. Analysis of the iron containing product isolated from the wheat bran extracts for inositol, phosphorus and iron gave molar ratios of 0.97 6.26 1, respectively, corresponding to a theoretical ratio of 1 6 1 for monoferric phytate. The isolated product exhibited a characteristic absorption spectrum in the 200- to 320-nm range (Figure 1) that corresponded to the spectrum for synthetic monoferric phytate. The Mbssbauer spectra (Figure 2) of the iron in wheat bran and of synthetic monoferric phytate also correspond (8). 

Left phytic acid (inositol hexaphosphate), the substrate of phytases. Right NMR spectra... 

Phytate or inositol hexaphosphate is a potential source of phosphorus present in many grains and seeds. The phytic acid is determined by treating the sample with EDTA and separation and quantitation using anion-exchange column (resin AG 1-X8 and eluent 0.8M NaCl) followed by reaction with a solution of ferric suLfosahcylate. The coloured complex can be observed in the UV range at 300 nm [22]. 

Myoinositol is a naturally occurring vitamin with a hexahydroxycyclohexane structure its phosphorylated forms are readily converted to trimethylsilyl derivatives which, as has been observed for alkyl ethoxy phosphates, can be separated by SFC at temperatures some hundreds of degrees below those necessary for GC of such compounds [14]. Both silylated inositol triphosphate and phytic acid (inositol hexaphosphate) were eluted... 

In animals, the myo-inositol is combined with phospholipids, while in plants it occurs mainly as salts of myo-inositol hexaphosphate, which is also known as phytic add (10.36a). 

The P absorbed by plant cells becomes involved in metabolic processes within a few minutes and the esters produced include phosphorylated sugars such as fructose-6-phosphate, phospholipids such as lecithin, nucleic acids and phytic acid salts (inositol hexaphosphates) (Chapter 10.1). 

Certain ions, e.g., oxalate and phosphate, can bind Ca within the intestinal canal and high intake of phosphate can restrict calcium absorption. A similar effect is encountered by phytic acid (inositol hexaphosphate) that is present in high amounts in certain cereals. Disturbances in the fat absorption (dietary) decreases the calcium absorption because Ca is bound to nonabsorbable fatty acids. 

Recently, the determination of phytic acid (myo-inositol hexaphosphate), which is believed to have an effect on the bioavailability of mineral substances, has become important. While phytic acid is not a food conshtuent in the United States, in other countries it is frequently added to foods as an anhoxidant [250,... 

Phytic acid (myo-inositol hexaphosphate) has been clearly established as a major phosphate reserve in many seeds, containing more than 50% of the total stored... 

Diets based on unleavened wheat bread contain a relatively large amount of phytic acid (inositol hexaphosphate), which can bind calcium, iron and zinc to form insoluble complexes that are not absorbed. Phytases in yeast catalyse dephosphorylation of phytate to products that do not chelate the minerals. 

Phosphates and phosphonates of biochemical interest and the forms adopted by ketose phosphates in aqueous solution have been discussed. The p a values of each of the six phosphoric monoester groups of wj o-inositol hexa-phosphate (phytic acid) have been determined by the use of P n.m.r. spectroscopy. The conformation adopted by myo-inositol hexaphosphate in basic and neutral solutions was also discussed. 

Phytic acid (wyo-inositol hexaphosphate) can be desymmetrized using phopha-tases found in Bakers yeast which allows the isolation of D-myo-inositol 1,2,6-trisphosphate. This was further used to prepare 3,4,5-tri-O-phenylcarbamoyl d-wyo-inositol. ... 

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