Phytic acid

Phytic acid is a six-fold dihydrogenphosphate ester of inositol (specifically, of the myo isomer), also called inositol hexakisphosphate (IP6) or inositol polyphosphate. At physiological pH, the phosphates are partially ionized, resulting in the phytate anion.

"IP6" redirects here. For the Internet Protocol revision, see IPv6.
Phytic acid
Ball-and-stick model of phytic acid
Space-filling model of phytic acid
Names
IUPAC name
(1R,2S,3r,4R,5S,6s)-cyclohexane-1,2,3,4,5,6-hexayl hexakis[dihydrogen (phosphate)]
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.001.369
E number E391 (antioxidants, ...)
UNII
Properties
C6H18O24P6
Molar mass 660.029 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references

The (myo) phytate anion is a colorless species that has significant nutritional role as the principal storage form of phosphorus in many plant tissues, especially bran and seeds. It is also present in many legumes, cereals, and grains. Phytic acid and phytate have a strong binding affinity to the dietary minerals, calcium, iron, and zinc, inhibiting their absorption.[1]

The lower inositol polyphosphates are inositol esters with less than six phosphates, such as inositol penta- (IP5), tetra- (IP4), and triphosphate (IP3). These occur in nature as catabolites of phytic acid.

Significance in agriculture
The hexavalent phytate anion.

Phosphorus and inositol in phytate form are not, in general, bioavailable to non-ruminant animals because these animals lack the digestive enzyme phytase required to hydrolyze the inositol-phosphate linkages. Ruminants are readily able to digest phytate because of the phytase produced by rumen microorganisms.[2]

In most commercial agriculture, non-ruminant livestock, such as swine, fowl, and fish,[3] are fed mainly grains, such as maize, legumes, and soybeans.[4] Because phytate from these grains and beans is unavailable for absorption, the unabsorbed phytate passes through the gastrointestinal tract, elevating the amount of phosphorus in the manure.[2] Excess phosphorus excretion can lead to environmental problems, such as eutrophication.[5] The use of sprouted grains will reduce the quantity of phytic acids in feed, with no significant reduction of nutritional value.[6]

Also, viable low-phytic acid mutant lines have been developed in several crop species in which the seeds have drastically reduced levels of phytic acid and concomitant increases in inorganic phosphorus.[7] However, germination problems have reportedly hindered the use of these cultivars thus far. This may be due to phytic acid's critical role in both phosphorus and metal ion storage.[8] Phytate variants also have the potential to be used in soil remediation, to immobilize uranium, nickel and other inorganic contaminants.[9]

Biological and physiological roles

Although indigestible for many animals, phytic acid and its metabolites as they occur in seeds and grains have several important roles for the seedling plant.

Most notably, phytic acid functions as a phosphorus store, as an energy store, as a source of cations and as a source of myo-inositol (a cell wall precursor). Phytic acid is the principal storage form of phosphorus in plant seeds.[10]

In animal cells, myo-inositol polyphosphates are ubiquitous, and phytic acid (myo-inositol hexakisphosphate) is the most abundant, with its concentration ranging from 10 to 100 μM in mammalian cells, depending on cell type and developmental stage.[11][12]

This compound is not obtained from the animal diet, but must be synthesized inside the cell from phosphate and inositol (which in turn is produced from glucose, usually in the kidneys). The interaction of intracellular phytic acid with specific intracellular proteins has been investigated in vitro, and these interactions have been found to result in the inhibition or potentiation of the physiological activities of those proteins.[13][14] The best evidence from these studies suggests an intracellular role for phytic acid as a cofactor in DNA repair by nonhomologous end-joining.[13] Other studies using yeast mutants have also suggested intracellular phytic acid may be involved in mRNA export from the nucleus to the cytosol.[15][16]

Inositol hexaphosphate facilitates the formation of the six-helix bundle and assembly of the immature HIV-1 Gag lattice. IP6 makes ionic contacts with two rings of lysine residues at the centre of the Gag hexamer. Proteolytic cleavage then unmasks an alternative binding site, where IP6 interaction promotes the assembly of the mature capsid lattice. These studies identify IP6 as a naturally occurring small molecule that promotes both assembly and maturation of HIV-1.[17]

Food science

Phytic acid was discovered in 1903.[18] Phytic acid, mostly as phytate in the form of phytin, is found within the hulls of seeds, including nuts, grains and pulses.[1] In-home food preparation techniques can break down the phytic acid in all of these foods. Simply cooking the food will reduce the phytic acid to some degree. More effective methods are soaking in an acid medium, sprouting and lactic acid fermentation such as in sourdough and pickling.[19] No detectable phytate (less than 0.02% of wet weight) was observed in vegetables such as scallion and cabbage leaves or in fruits such as apples, oranges, bananas, or pears.[20]

As a food additive, phytic acid is used as the preservative, E391.[21][22]

Dry food sources of phytic acid[23][20][24][25][26][27][28][29]
Food Proportion by weight (g/100 g)
Min. Max.
Pumpkin seed4.34.3
Linseed2.152.78
Sesame seeds flour5.365.36
Chia seeds0.961.16
Almonds1.353.22
Brazil nuts1.976.34
Coconut0.360.36
Hazelnut0.650.65
Peanut0.951.76
Walnut0.980.98
Maize (corn)0.752.22
Oat0.421.16
Oat meal0.892.40
Brown rice0.840.99
Polished rice0.140.60
Wheat0.391.35
Wheat flour0.251.37
Wheat germ0.081.14
Whole wheat bread0.431.05
Beans, pinto2.382.38
Buckwheat1.001.00
Chickpeas0.560.56
Lentils0.440.50
Soybeans1.002.22
Tofu1.462.90
Soy beverage1.241.24
Soy protein concentrate1.242.17
New potato0.180.34
Spinach0.22NR
Avocado fruit0.510.51
Chestnuts[30] 0.47
Fresh food sources of phytic acid[25]
Food Proportion by weight (%)
Min. Max.
Taro0.1430.195
Cassava0.1140.152

Dietary mineral absorption

Phytic acid has a strong binding affinity to the dietary minerals, calcium, iron, and zinc, inhibiting their absorption.[1][31] Phytochemicals like polyphenols and tannins also influence the binding.[32] When iron and zinc bind to phytic acid, they form insoluble precipitates and are far less absorbable in the intestines. This process can therefore contribute to iron and zinc deficiencies in people whose diets rely on these foods for their mineral intake, such as those in developing countries[33][34] and vegetarians.[35]

Human nutrition

Because phytic acid can affect the absorption of iron, "dephytinization should be considered as a major strategy to improve iron nutrition during the weaning period".[36] Dephytinization by exogenous phytase to phytate-containing food is an approach being investigated to improve nutritional health in populations that are vulnerable to mineral deficiency due to their reliance on phytate-laden food staples. Crop breeding to increase mineral density (biofortification) or reducing phytate content are under preliminary research.[37]

gollark: Oh, for IO, neat. I wonder why that hasn't really taken off yet.
gollark: Unless you count whatever "silicon photonics" stuff Intel is doing for 400GbE and such.
gollark: Delayed again? I don't think the technology exists at all now.
gollark: 3nm and below will apparently use GAAFETs, which are a new design of transistor which will improve things somewhat.
gollark: Bottom of the range dedicated GPUs are (still) £30 or so.

See also

References
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  3. Romarheim OH, Zhang C, Penn M, Liu YJ, Tian LX, Skrede A, Krogdahl Å, Storebakken T (2008). "Growth and intestinal morphology in cobia (Rachycentron canadum) fed extruded diets with two types of soybean meal partly replacing fish meal". Aquaculture Nutrition. 14 (2): 174–180. doi:10.1111/j.1365-2095.2007.00517.x.
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  8. Shitan, Nobukazu; Yazaki, Kazufumi (2013-01-01), Jeon, Kwang W. (ed.), "Chapter Nine - New Insights into the Transport Mechanisms in Plant Vacuoles", International Review of Cell and Molecular Biology, Academic Press, 305, pp. 383–433, retrieved 2020-04-24
  9. Seaman JC, Hutchison JM, Jackson BP, Vulava VM (2003). "In situ treatment of metals in contaminated soils with phytate". Journal of Environmental Quality. 32 (1): 153–61. doi:10.2134/jeq2003.0153. PMID 12549554.
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  14. Norris FA, Ungewickell E, Majerus PW (January 1995). "Inositol hexakisphosphate binds to clathrin assembly protein 3 (AP-3/AP180) and inhibits clathrin cage assembly in vitro". The Journal of Biological Chemistry. 270 (1): 214–7. doi:10.1074/jbc.270.1.214. PMID 7814377.
  15. York JD, Odom AR, Murphy R, Ives EB, Wente SR (July 1999). "A phospholipase C-dependent inositol polyphosphate kinase pathway required for efficient messenger RNA export". Science. 285 (5424): 96–100. doi:10.1126/science.285.5424.96. PMID 10390371.
  16. Shears SB (March 2001). "Assessing the omnipotence of inositol hexakisphosphate". Cellular Signalling (Submitted manuscript). 13 (3): 151–8. doi:10.1016/S0898-6568(01)00129-2. PMID 11282453.
  17. Dick RA, Zadrozny KK, Xu C, Schur FK, Lyddon TD, Ricana CL, Wagner JM, Perilla JR, Ganser-Pornillos BK, Johnson MC, Pornillos O, Vogt VM (August 2018). "Inositol phosphates are assembly co-factors for HIV-1". Nature. 560 (7719): 509–512. doi:10.1038/s41586-018-0396-4. PMC 6242333. PMID 30069050.
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  21. Functional Food - Improve Health through Adequate Food edited by María Chávarri Hueda, pg. 86
  22. https://noshly.com/additive/391/preservative/391/
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  28. Arendt EK, Zannini E (2013-04-09). "Chapter 11: Buckwheat". Cereal grains for the food and beverage industries. Woodhead Publishing. p. 388. ISBN 978-0-85709-892-4.
  29. Pereira Da Silva B. Concentration of nutrients and bioactive compounds in chia (Salvia Hispanica L.), protein quality and iron bioavailability in wistar rats (Ph.D. thesis). Federal University of Viçosa.
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  31. Gupta, R. K.; Gangoliya, S. S.; Singh, N. K. (2013). "Reduction of phytic acid and enhancement of bioavailable micronutrients in food grains". Journal of Food Science and Technology. 52 (2): 676–684. doi:10.1007/s13197-013-0978-y. PMC 4325021. PMID 25694676.
  32. Prom-u-thai C, Huang L, Glahn RP, Welch RM, Fukai S, Rerkasem B (2006). "Iron (Fe) bioavailability and the distribution of anti-Fe nutrition biochemicals in the unpolished, polished grain and bran fraction of five rice genotypes". Journal of the Science of Food and Agriculture. 86 (8): 1209–15. doi:10.1002/jsfa.2471.
  33. Hurrell RF (September 2003). "Influence of vegetable protein sources on trace element and mineral bioavailability". The Journal of Nutrition. 133 (9): 2973S–7S. doi:10.1093/jn/133.9.2973S. PMID 12949395.
  34. Committee on Food Protection; Food and Nutrition Board; National Research Council (1973). "Phytates". Toxicants Occurring Naturally in Foods. National Academy of Sciences. pp. 363–371. ISBN 978-0-309-02117-3.
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