Phytic acid is a six-fold dihydrogenphosphate ester of

inositol Inositol, or more precisely ''myo''-inositol, is a carbocyclic sugar that is abundant in the brain and other mammalian tissues; it mediates cell signal transduction in response to a variety of hormones, neurotransmitters, and growth factors and ...

(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 An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

. 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 Bran, also known as miller's bran, is the hard outer layers of cereal grain. It consists of the combined aleurone and pericarp. Corn (maize) bran also includes the pedicel (tip cap). Along with germ, it is an integral part of whole grains, ...

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 In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight (oxygen, hydrogen, carbon, ...

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...

, iron, and zinc, inhibiting their

absorption Absorption may refer to: Chemistry and biology *Absorption (biology), digestion **Absorption (small intestine) *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a route by which s ...

in the small intestine. 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

Phytic acid was discovered in 1903. Generally, phosphorus and inositol in phytate form are not

bioavailable In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation. By definition, when a medication is administered intravenously, its bioavailability is 100%. Ho ...

to non- ruminant animals because these animals lack the enzyme phytase required to hydrolyze the inositol-phosphate linkages. Ruminants are able to digest phytate because of the phytase produced by rumen microorganisms. In most commercial

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...

, non-ruminant livestock, such as swine,

fowl Fowl are birds belonging to one of two biological orders, namely the gamefowl or landfowl (Galliformes) and the waterfowl (Anseriformes). Anatomical and molecular similarities suggest these two groups are close evolutionary relatives; together ...

, and fish, are fed mainly grains, such as maize, legumes, and soybeans. 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. Excess phosphorus excretion can lead to environmental problems, such as eutrophication. The use of sprouted grains may reduce the quantity of phytic acids in feed, with no significant reduction of nutritional value. 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. 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. Phytate variants also have the potential to be used in soil remediation, to immobilize uranium, nickel, and other inorganic contaminants.

Biological and physiological roles

Although indigestible for many animals as they occur in seeds and grains, phytic acid and its metabolites 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. 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. 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. The best evidence from these studies suggests an intracellular role for phytic acid as a cofactor in DNA repair by nonhomologous end-joining. Other studies using yeast mutants have also suggested intracellular phytic acid may be involved in mRNA export from the nucleus to the cytosol. 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.

Dentistry

IP6 has potential use in endodontics, adhesive, preventive, and regenerative dentistry, and in improving the characteristics and performance of dental materials.

Food science

Phytic acid, mostly as phytate in the form of phytin, is found within the

hull Hull may refer to: Structures * Chassis, of an armored fighting vehicle * Fuselage, of an aircraft * Hull (botany), the outer covering of seeds * Hull (watercraft), the body or frame of a ship * Submarine hull Mathematics * Affine hull, in affi ...

s and kernels of seeds, including nuts, grains, and pulses. In-home food preparation techniques may 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 Sourdough or sourdough bread is a bread made by the fermentation of dough using wild lactobacillaceae and yeast. Lactic acid from fermentation imparts a sour taste and improves keeping qualities. History In the ''Encyclopedia of Food Microbiolo ...

and pickling. 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. As a food additive, phytic acid is used as the preservative, E391. : :

Dietary mineral absorption

Phytic acid has a strong affinity to the

, iron, and zinc, inhibiting their

from the small intestine. Phytochemicals such as polyphenols and tannins also influence the binding. When iron and zinc bind to phytic acid, they form insoluble precipitates and are far less absorbable in the intestines. Because phytic acid also can affect the absorption of iron, "dephytinization should be considered as a major strategy to improve iron nutrition during the weaning period". 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 Plant breeding is the science of changing the traits of plants in order to produce desired characteristics. It has been used to improve the quality of nutrition in products for humans and animals. The goals of plant breeding are to produce cro ...

to increase mineral density (

biofortification Biofortification is the idea of breeding crops to increase their nutritional value. This can be done either through conventional selective breeding, or through genetic engineering. Biofortification differs from ordinary fortification because it ...

) or reducing phytate content are under preliminary research.

References