A polyol or polyalcohol or glycol is a chemical compound organic characterized by a certain number of groups - OH (groups Hydroxyle S).

Of general Chemical formula; C n H 2n+2 O n, they have at least two groupings alcohol.

Aldehyde gold Ketone, Reducing sugar) has been reduced to has primary gold secondary Hydroxyl group. They are commonly used for replacing sucrose in foodstuffs, often in combination with high intensity Artificial sweetener S to counter the low sweetness. -->

Toxicology

Some ethers of glycol are particularly Toxique S, just as some of their Métabolite S.

Ecotoxicology

Examples

(The maltitol and the lactitol are not completely hydrogenated; it is about Monosaccharide S combined with an alcohol polyhydric.)

The term is however also used for a certain number of Polymère S which one obtains by addition of oxides of olefinic hydrocarbons to a sugar for example but also of glycerol. Typical examples are the Oxyde of polyethylene or Polyéthylène glycol (PEG), the Polypropylène glycol (PPG) and the Polytétraméthylène glycol (PTMG).

Polyurethane foams

The polyols are used as bases in industry for the realization of polyurethane foams while adding to it of isocyanate for polymerization.

The polyol is used as basic chain with the polymer, whose property vary according to the length of chain.

Polyols as food additives

Candy gold Chewing gum. Sugar alcohols boat oral Be metabolized by bacteria, and so they C not contribute to tooth decay.

Internal Sugar alcohols are usually incompletely digested in the S by Insulin - independent means, resulting in little changes in blood glucose. This property makes them popular sweeteners among diabetic S and people one Low-carbohydrate diet S. However, digestible ace for many other incompletely substances (such ace Dietary fiber), overconsumption off sugar alcohols edge lead to Bloating and Diarrhea. With continued uses, most people develop has tolerance to sugar alcohols and No to skirt experiment thesis symptoms. Ace year exception, erythritol is lost through urine.

The counts At right off present the relative sweetness and measured caloric content the most widely-used sugar alcohols. Although the caloric been worth differ, HAVE labeling requirements assign has off blanket been worth 2.4 kcal/g to all sugar alcohols. -->

Polyols at the Plants

The plants have faculty to synthesize their biomass starting from the simple mineral molecules (water, rock salt of the ground and carbon dioxide). This autotrophie rests on a pigment located in the Chloroplaste, the chlorophyl which uses the light as energy source and transforms it into chemical energy via the chain of the Photosynthèse. During photosynthesis, the atmospheric carbon dioxide absorptive by the stomata of the sheets is combined with hydrogen coming from the photolysis of water. This reaction leads to an oxygen release and the reduction of the carbonic gas which results in the formation of trioses precursory phosphates of the Cycle of Calvin in the chloroplast. The trioses phosphates are transformed into starch transitory or exported in the cytosol to give saccharose, principal transport with long distance of carbon forms. The night, the starch is evacuated towards the cytoplasm in the form of glucose which can be degraded by the Glycolyse to provide energy to the cell, or synthesized in Saccharose. At certain plants, the role of transport with long distance of carbon is ensured, parallel to saccharose, by tridiholosides drifting of saccharose by addition of one or two molecules of galactose or by polyols like the mannitol and the sorbitol.

Natural biochemical of the polyols

The polyols are regarded as derivatives of Ose S and are obtained by the reduction of the grouping aldehyde or ketone of a glucid. The polyols can be classified in two groups:

- aliphatic alditols or polyols which have a linear chain of carbon atoms

- cyclic cyclitols or polyols which are derivatives of cyclohexane.

According to the length of their carbonaceous chain, the alditols are indicated under the name of pentitols, hexitols, heptitols, etc the most current alditols at the plants are the hexitols (chain with six carbon atoms). Each aldose produces only one alditol whose name derives from this ose, for example mannose gives the mannitol.

It was estimated that approximately 30% of the primary production of carbon on ground passed by the polyol synthesis at the plants and the algae (Bieleski, 1982). The polyols are present in the whole of the vegetable world and mycelial. Thus, at mushrooms, the lichens and much of marine algas, the polyols often constitute the main thing assimilat. At the higher plants, 17 alditols were identified including 13 at the angiospermes (LEWIS, 1984). Most frequently met are:

- the galactitol, especially present at Célastracées (charcoal), Scrofulariacées (muflier, digital) and Orobanchacées (broomrape)

- the sorbitol, the main thing produces photosynthetic at several woody species of Rosacées like the apple tree (Malus), the pear tree (Pyrus), the plum tree (Prunus).

- the mannitol, present in a hundred species of higher plants of which Rubiacées (coffee-tree), Oléacées (privet, ash, olive-tree) and Apiacées (celery, carrot, parsley).

Roles of the polyols

At the plants, the physiological roles suggested for polyols are multiple: intervention in the tolerance with the abiotic and biotic stresses and forms transport and of storage of carbonaceous skeletons.

Tolerance with the saline stress:

Many environmental stresses to which the plants are subjected seem to lead to a reduction in the hydrous potential. According to the plant species, the sensitivity of the plants and their answer to the changes of hydrous potential which had with the dryness, the low temperatures or a raised salinity, vary. However, one of the means used by organizations such as mushrooms, the algae, the higher plants to tolerate these stresses is the synthesis and the accumulation of soluble compounds of weak molecular weights to increase the osmotic Potentiel cells and to maintain the Turgescence. These compounds are called compatible aqueous solutions. They are osmotiquement active and they can accumulate with very high concentrations in the cytosol without to interfere with the cellular metabolism. Among these compounds the mannitol (acyclic polyol) is, as well as other inorganic substances (ions) or organics (hexoses and unquestionable amino-acid) also being able to intervene in the osmotic adjustment.

See too

  • Ether of glycol

External bonds

  • page of caducée.net
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