Names | |
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IUPAC name myo-Inositol | |
Systematic IUPAC name (1R,2S,3r,4R,5S,6s)-Cyclohexane-1,2,3,4,5,6-hexol | |
Other names cis-1,2,3,5-trans-4,6-Cyclohexanehexol Cyclohexanehexol Mouse antialopecia factor Nucite Phaseomannite Phaseomannitol Rat antispectacled eye factor Scyllite (for the isomer scyllo-inositol) Vitamin B8 | |
Identifiers | |
3D model (JSmol) | |
ChEBI | |
ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.027.295 |
KEGG | |
PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
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Properties | |
C6H12O6 | |
Molar mass | 180.16 g/mol |
Density | 1.752 g/cm3 |
Melting point | 225 to 227 °C (437 to 441 °F; 498 to 500 K) |
Thermochemistry [2] | |
Std enthalpy of formation (ΔfH⦵298) | −1329.3 kJ/mol |
Std enthalpy of combustion (ΔcH⦵298) | −2747 kJ/mol |
Pharmacology | |
A11HA07 ( WHO ) | |
Hazards | |
NFPA 704 (fire diamond) | |
Flash point | 143 °C (289 °F; 416 K) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Inositol, primarily the isomer 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 participates in osmoregulation. [3] Concerning regulation of osmosis, in most mammalian cells the intracellular concentrations of myo-inositol are 5 to 500 times greater than the extracellular concentrations. [4]
It is a sugar alcohol with half the sweetness of sucrose (table sugar). Inositol was once considered to be a B8 vitamin [5] before the discovery that it is made naturally in the human body from glucose, and therefore cannot be a vitamin. A human kidney makes about two grams per day. Other tissues synthesize it too, and the highest concentration is in the brain, where it plays an important role in making other neurotransmitters and some steroid hormones bind to their receptors. [6]
Inositol is promoted as a dietary supplement in the management of polycystic ovary syndrome (PCOS). However, there is only evidence of very low quality for its efficacy in increasing fertility for IVF in women with PCOS. [7]
myo-Inositol plays an important role as the structural basis for a number of secondary messengers in eukaryotic cells, the various inositol phosphates. In addition, inositol serves as an important component of the structural lipids phosphatidylinositol (PI) and its various phosphates, the phosphatidylinositol phosphate (PIP) lipids.
Inositol or its phosphates and associated lipids are found in many foods, in particular fruit, especially cantaloupe and oranges. [8] In plants, the hexaphosphate of inositol, phytic acid or its salts, the phytates, serve as phosphate stores in seed, for example in nuts and beans. [9] Phytic acid also occurs in cereals with high bran content. Phytate is, however, not directly bioavailable to humans in the diet, since it is not digestible. Some food preparation techniques partly break down phytates to change this. However, inositol in the form of glycerophospholipids, as found in certain plant-derived substances such as lecithins, is well absorbed and relatively bioavailable.
myo-Inositol (free of phosphate) was once considered a member of the vitamin B complex, called vitamin B8 in this context. However, because it is produced by the human body from glucose, it is not an essential nutrient. [10]
myo-Inositol is the biologically important form of cyclohexane-1,2,3,4,5,6-hexol. It is a meso compound, meaning it is optically inactive because it has a plane of symmetry. It was formerly called meso-inositol, but because there are other meso isomers, myo-inositol is now the preferred name. Besides myo-inositol, the other naturally occurring stereoisomers are scyllo-, muco-, D-chiro-, L-chiro-, and neo-inositol, although they occur in minimal quantities in nature. The other possible isomers are allo-, epi-, and cis-inositol. As their names denote, L- and D-chiro inositol are the only pair of enantiomers (mirror-image forms). All the others are meso compounds. [11]
In its most stable conformation, the myo-inositol isomer assumes the chair conformation, which moves the maximum number of hydroxyls to the equatorial position, where they are farthest apart from each other. In this conformation, the natural myo isomer has a structure in which five of the six hydroxyls (the first, third, fourth, fifth, and sixth) are equatorial, whereas the second hydroxyl group is axial. [12]
In humans, myo-Inositol is synthesized de novo but D-chiro-inositol is not. [4] myo-Inositol is synthesized from glucose 6-phosphate (G6P) in two steps. First, G6P is isomerised by an inositol-3-phosphate synthase enzyme (for example, ISYNA1) to myo-inositol 1-phosphate, which is then dephosphorylated by an inositol monophosphatase enzyme (for example, IMPA1) to give free myo-inositol. In humans, most inositol is synthesized in the kidneys, followed by testicles, typically in amounts of a few grams per day. [3]
At the peripheral level, myo-inositol is converted to D-chiro-inositol by a specific epimerase. Only a minor fraction of myo-inositol is converted into D-chiro-inositol. [4] The activity of this epimerase is insulin dependent, causing a reduction of D-chiro-inositol in muscle, fat, and liver when there is insulin resistance. [13] [4] D-chiro-inositol reduces the conversion of testosterone to estrogen, thereby increases the levels of testosterone and worsening PCOS. [4]
Inositol hexaphosphate, also called phytic acid or IP6, is a phytochemical and the principal storage form of phosphorus in many plant tissues, especially bran and seed. [14] Phosphorus and inositol in phytate form are not generally bioavailable to non-ruminant animals because these animals lack the digestive enzyme phytase required to remove the phosphate groups. Ruminants are readily able to digest phytate because of the phytase produced by microorganisms in the rumen. [15] Moreover, phytic acid also chelates important minerals such as calcium, magnesium, iron, and zinc, making them unabsorbable, and contributing to mineral deficiencies in people whose diets rely highly on bran and seeds for their mineral intake, such as occurs in developing countries. [16] [17]
Inositol penta- (IP5), tetra- (IP4), and triphosphate (IP3) are also called "phytates".
Inositol, phosphatidylinositol and some of their mono- and polyphosphates function as secondary messengers in a number of intracellular signal transduction pathways. They are involved in a number of biological processes, including:
In one important family of pathways, phosphatidylinositol 4,5-bisphosphate (PIP2) is stored in cellular membranes until it is released by any of a number of signalling proteins and transformed into various secondary messengers, for example diacylglycerol and inositol triphosphate. [24]
At the 1936 meeting of the American Chemical Society, professor Edward Bartow of the University of Iowa presented a commercially viable means of extracting large amounts of inositol from the phytic acid naturally present in waste corn. As a possible use for the chemical, he suggested 'inositol nitrate' as a more stable alternative to nitroglycerin. [25] Today, inositol nitrate is used to gelatinize nitrocellulose in many modern explosives and solid rocket propellants. [26]
When plants are exposed to increasing concentrations of road salt, the plant cells become dysfunctional and undergo apoptosis, leading to inhibited growth. Inositol pretreatment could reverse these effects. [27]
Large doses of inositol have been studied for treatment of depression, but further study is needed to determine whether this is an effective treatment. [28]
Inositol has been found to have modest to moderate effects in patients with panic disorder or obsessive-compulsive disorder. [29] [30]
High doses of inositol are sometimes used to treat trichotillomania (compulsive hair-pulling) and related disorders, [31] but a small (N=38) double-blinded placebo-controlled trial did not find a statistically significant improvement with inositol. [32]
D-chiro-inositol is an important messenger molecule in insulin signaling. [33] Inositol supplementation has been shown to significantly decrease triglycerides and LDL cholesterol in patients with metabolic diseases. [33]
myo-Inositol is important for thyroid hormone synthesis. [34] Depletion of myo-inositol may predispose to development of hypothyroidism. [34] Patients with hypothyroidism have a higher demand for myo-inositol than healthy subjects. [34]
Inositol should not be routinely implemented for the management of preterm babies who have or are at a risk of infant respiratory distress syndrome (RDS). [35] Myo-inositol helps prevent neural tube defects with particular efficacy in combination with folic acid. [36]
Inositol is considered a safe and effective treatment for polycystic ovary syndrome (PCOS). [37] It works by increasing insulin sensitivity, which helps to improve ovarian function and reduce hyperandrogenism. [38] It is also shown to reduce the risk of metabolic disease in women with PCOS. [39] In addition, thanks to its role as FSH second messenger, myo-inositol is effective in restoring FSH/LH ratio and menstrual cycle regularization. [40] myo-Inositol's role as FSH second messenger leads to a correct ovarian follicle maturation and consequently to a higher oocyte quality. Improving the oocyte quality in both women with or without PCOS, myo-inositol can be considered as a possible approach for increasing the chance of success in assisted reproductive technologies. [41] [42] In contrast, D-chiro-inositol can impair oocyte quality in a dose-dependent manner. [43] The high level of DCI seems to be related to elevated insulin levels retrieved in about 70% of PCOS women. [44] In this regard, insulin stimulates the irreversible conversion of myo-inositol to D-chiro-inositol causing a drastic reduction of myo-inositol. myo-Inositol depletion is particularly damaging to ovarian follicles because it is involved in FSH signaling, which is impaired due to myo-inositol depletion. [13] Recent evidence reports a faster improvement of the metabolic and hormonal parameters when these two isomers are administered in their physiological ratio. The plasmatic ratio of myo-inositol and D-chiro-inositol in healthy subjects is 40:1 of myo- and D-chiro-inositol respectively. [45] The use of the 40:1 ratio shows the same efficacy of myo-inositol alone but in a shorter time. In addition, the physiological ratio does not impair oocyte quality. [46]
The use of inositols in PCOS is gaining more importance, and an efficacy higher than 70% with a strong safety profile is reported. On the other hand, about 30% of patients could show as inositol-resistant. [47] New evidence regarding PCOS aetiopathogenesis describes an alteration in the species and the quantity of each strain characterizing the normal gastrointestinal flora. This alteration could lead to chronic, low-level inflammation and malabsorption. [48] A possible solution could be represented by the combination of myo-inositol and α-lactalbumin. This combination shows a synergic effect in increasing myo-inositol absorption. [49] A recent study reported that the myo-inositol and α-lactalbumin combination is able to increase myo-inositol plasmatic content in inositol-resistant patients with a relative improvement of hormonal and metabolic parameters. [50]
Despite its antinutrient effect, phytic acid has potential uses in endodontics, adhesive, preventive, and regenerative dentistry, and in improving the characteristics and performance of dental materials. [51]
Inositol has been used as an adulterant or cutting agent for many illegal drugs, such as cocaine, methamphetamine, and sometimes heroin, [52] probably because of its solubility, powdery texture, or reduced sweetness (50%) compared to more common sugars.
Inositol is also used as a stand-in film prop for cocaine in filmmaking. [53] [54]
myo-Inositol is naturally present in a variety of foods, although tables of food composition do not always distinguish between lecithin, the relatively bioavailable lipid form and the biounavailable phytate/phosphate form. [8] Foods containing the highest concentrations of myo-inositol and its compounds include fruits, beans, grains, and nuts. [8] Fruits in particular, especially oranges and cantaloupe, contain the highest amounts of myo-inositol. [55] It is also present in beans, nuts, and grains, however, these contain large amounts of myo-inositol in the phytate form, which is not bioavailable without transformation by phytase enzymes. Bacillus subtilis, the microorganism which produces the fermented food natto, produces phytase enzymes that may convert phytic acid to a more bioavailable form of inositol polyphosphate in the gut. [56] Additionally, Bacteroides species in the gut secrete vesicles containing an active enzyme which converts the phytate molecule into bioavailable phosphorus and inositol polyphosphate, which is an important signaling molecule in the human body. [57]
myo-Inositol can also be found as an ingredient in energy drinks, [58] either in conjunction with or as a substitute for glucose. [59]
In humans, myo-inositol is naturally made from glucose-6-phosphate through enzymatic dephosphorylation. [55]
Polycystic ovary syndrome, or polycystic ovarian syndrome (PCOS), is the most common endocrine disorder in women of reproductive age. The syndrome is named after cysts which form on the ovaries of some people with this condition, though this is not a universal symptom, and not the underlying cause of the disorder.
Hirsutism is excessive body hair on parts of the body where hair is normally absent or minimal. The word is from early 17th century: from Latin hirsutus meaning "hairy". It usually refers to a male pattern of hair growth in a female that may be a sign of a more serious medical condition, especially if it develops well after puberty. Cultural stigma against hirsutism can cause much psychological distress and social difficulty. Discrimination based on facial hirsutism often leads to the avoidance of social situations and to symptoms of anxiety and depression.
Anovulation is when the ovaries do not release an oocyte during a menstrual cycle. Therefore, ovulation does not take place. However, a woman who does not ovulate at each menstrual cycle is not necessarily going through menopause. Chronic anovulation is a common cause of infertility.
Phosphatidylinositol or inositol phospholipid is a biomolecule. It was initially called "inosite" when it was discovered by Léon Maquenne and Johann Joseph von Scherer in the late 19th century. It was discovered in bacteria but later also found in eukaryotes, and was found to be a signaling molecule.
Hyperandrogenism is a medical condition characterized by high levels of androgens. It is more common in women than men. Symptoms of hyperandrogenism may include acne, seborrhea, hair loss on the scalp, increased body or facial hair, and infrequent or absent menstruation. Complications may include high blood cholesterol and diabetes. It occurs in approximately 5% of women of reproductive age.
Fertility medications, also known as fertility drugs, are medications which enhance reproductive fertility. For women, fertility medication is used to stimulate follicle development of the ovary. There are very few fertility medication options available for men.
Phytic acid is a six-fold dihydrogenphosphate ester of inositol, also called inositol hexaphosphate, inositol hexakisphosphate (IP6) or inositol polyphosphate. At physiological pH, the phosphates are partially ionized, resulting in the phytate anion.
Inositol phosphates are a group of mono- to hexaphosphorylated inositols. Each form of inositol phosphate is distinguished by the number and position of the phosphate group on the inositol ring.
A phytase is any type of phosphatase enzyme that catalyzes the hydrolysis of phytic acid – an indigestible, organic form of phosphorus that is found in many plant tissues, especially in grains and oil seeds – and releases a usable form of inorganic phosphorus. While phytases have been found to occur in animals, plants, fungi and bacteria, phytases have been most commonly detected and characterized from fungi.
Inositol oxygenase, also commonly referred to as myo-inositol oxygenase (MIOX), is a non-heme di-iron enzyme that oxidizes myo-inositol to glucuronic acid. The enzyme employs a unique four-electron transfer at its Fe(II)/Fe(III) coordination sites and the reaction proceeds through the direct binding of myo-inositol followed by attack of the iron center by diatomic oxygen. This enzyme is part of the only known pathway for the catabolism of inositol in humans and is expressed primarily in the kidneys. Recent medical research regarding MIOX has focused on understanding its role in metabolic and kidney diseases such as diabetes, obesity and acute kidney injury. Industrially-focused engineering efforts are centered on improving MIOX activity in order to produce glucaric acid in heterologous hosts.
1D-chiro-Inositol is a member of a family of related substances often referred to collectively as "inositol", although that term encompasses several isomers of questionable biological relevance, including 1L-chiro-inositol. myo-Inositol is converted into DCI by an insulin dependent NAD/NADH epimerase enzyme. It is known to be an important secondary messenger in insulin signal transduction. DCI accelerates the dephosphorylation of glycogen synthase and pyruvate dehydrogenase, rate limiting enzymes of non-oxidative and oxidative glucose disposal. DCI may act to bypass defective normal epimerization of myo-inositol to DCI associated with insulin resistance and at least partially restore insulin sensitivity and glucose disposal. One pilot study found males taking it had increased androgens and reduced estrogen.
The enzyme 3-phytase (EC 3.1.3.8) catalyzes the reaction
The enzyme 4-phytase (EC 3.1.3.26) catalyzes the following reaction:
The enzyme 5-phytase (EC 3.1.3.72) catalyzes the reaction
Hyperthecosis, or ovarian hyperthecosis, is hyperplasia of the theca interna of the ovary. Hyperthecosis occurs when an area of luteinization occurs along with stromal hyperplasia. The luteinized cells produce androgens, which may lead to hirsutism and virilization in affected women.
Ovarian drilling, also known as multiperforation or laparoscopic ovarian diathermy, is a surgical technique of puncturing the membranes surrounding the ovary with a laser beam or a surgical needle using minimally invasive laparoscopic procedures. It differs from ovarian wedge resection, which involves the cutting of tissue. Minimally invasive ovarian drilling procedures have replaced wedge resections. Ovarian drilling is favored over wedge resection because cutting into the ovary might result in adhesions, potentially complicating postoperative outcomes. Ovarian drilling and ovarian wedge resection are treatment options to reduce the amount of androgen producing tissue in women with polycystic ovarian syndrome (PCOS). PCOS is the primary cause of anovulation, which results in female infertility. The induction of mono-ovulatory cycles can restore fertility.
Infertility in polycystic ovary disease (PCOS) is a hormonal imbalance in women that is thought to be one of the leading causes of female infertility. Polycystic ovary syndrome causes more than 75% of cases of anovulatory infertility.
Obesity is defined as an abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight. This is often described as a body mass index (BMI) over 30. However, BMI does not account for whether the excess weight is fat or muscle, and is not a measure of body composition. For most people, however, BMI is an indication used worldwide to estimate nutritional status. Obesity is usually the result of consuming more calories than the body needs and not expending that energy by doing exercise. There are genetic causes and hormonal disorders that cause people to gain significant amounts of weight but this is rare. People in the obese category are much more likely to suffer from fertility problems than people of normal healthy weight.
The HAIR-AN syndrome is a rare subtype of polycystic ovary syndrome (PCOS) characterized by hyperandrogenism (HA), insulin resistance (IR) and acanthosis nigricans (AN). The symptoms of the HAIR-AN syndrome are largely due to severe insulin resistance, which can be secondary to blocking antibodies against the insulin receptor or genetically absent/reduced insulin receptor number/function. Insulin resistance leads to hyperinsulinemia which, in turn, leads to an excess production of androgen hormones by the ovaries. High levels of androgen hormones (hyperandrogenism) in females causes excessive hair growth, acne and irregular menstruation. Patients with both underlying mechanisms of insulin resistance may have more severe hyperandrogenism. Insulin resistance is also associated with diabetes, heart disease and excessive darkening of the skin
β-propeller phytases (BPPs) are a group of enzymes (i.e. protein superfamily) with a round beta-propeller structure. BPPs are phytases, which means that they are able to remove (hydrolyze) phosphate groups from phytic acid and its phytate salts. Hydrolysis happens stepwise and usually ends in myo-inositol triphosphate product which has three phosphate groups still bound to it. The actual substrate of BPPs is calcium phytate and in order to hydrolyze it, BPPs must have Ca2+ ions bound to themselves. BPPs are the most widely found phytase superfamily in the environment and they are thought to have a major role in phytate-phosphorus cycling in soil and water. As their alternative name alkaline phytase suggests, BPPs work best in basic (or neutral) environment. Their pH optima is 6–9, which is unique among the phytases.
An isomer of glucose that has traditionally been considered to be a B vitamin although it has an uncertain status as a vitamin has not been identified in man