Xylitol

• Xylitol
• (2R, 3R, 4S) -pentane -1 ,2,3,4,5 - pentol
• Xylo -1 ,2,3,4,5 - pentanepentol
• E 967

Colorless, sweet-tasting crystals

Fixed

1.52 g · cm -3

94 ° C

216 ° C

• Slightly soluble in water and pyridine
• Little in alcohol

12,500 mg · kg -1 ( LD50, rat, oral)

Template: Infobox chemical / molecular formula search available

Xylitol, also called xylitol or birch sugar, is a common name of pentanepentol stereoisomer, a sugar alcohol as a sugar substitute ( E 967 ) is used. The discovery dates back to the later Nobel Prize winner Emil Fischer.

The specificity of xylitol is its proven in several clinical studies cariostatic and anti-cariogenic activity. In some mammals, especially dogs, xylitol acts, however, toxic ( see veterinary importance ).

Discovery

Xylitol was first isolated in 1890 by Emil Fischer and his Ph.D. student Rudolf Stahel from beech wood chips. Their discovery, which they called xylitol, they published in 1891. Around the same time as Fischer and Stahel isolated by the French chemist MG Bertrand from wheat and oat straws a kind of xylitol syrup.

Occurrence and production

Xylitol is next sorbitol as a natural sugar alcohol in many vegetables ( and Others cauliflower) and fruits ( inter alia, plums, strawberries, raspberries ), where the proportion is less than 1 % in the dry matter, and in the bark of certain species of wood (eg birch). Industrial Xylitol is obtained by chemical modification of xylans ( rubber wood ) over the wood sugar xylose. The industrial production is complex, xylitol is a relatively more expensive sugar substitute. Today, the collection is often carried out remains of corn cobs after harvesting the grains. Another possible the use of genetically modified maize.

As intermediate 5-15 grams daily are produced in the liver in the human body during the carbohydrate degradation.

Properties

Chemically, xylitol is a pentitol and is one of the sugar alcohols. The molecule is located in a pseudoasymmetrisch achiral meso form. The achiral form of pentitol is ribitol, arabitol the chiral form.

Xylitol has a similar taste and nearly the same sweetening power as sucrose. Xylitol dissolves in the mouth in saliva, it draws heat from the environment and produces a cooling effect on the tongue ( endothermic heat of solution ) of -153.2 J / g, which is similar to that described the effect of menthol.

The related nutritional value of 10 kJ / g (2.4 kcal / g) is 40 % lower than table sugar (sucrose). The metabolic pathway in the human body runs independently from insulin, affects blood sugar and insulin levels only slightly and is therefore suitable for diabetics.

Xylitol is heat stable and caramelized only when it is heated to over 200 ° C for several minutes. At temperatures of about 100 ° C, no caramelisation takes place. In the pure state, it is in the form of hygroscopic crystals.

Xylitol is a molecule that is able to bind much water per se. It is only passive, so absorbed slowly and incompletely in the small intestine. With regular use of the rate of absorption can be increased by enzyme induction in the small intestine. Taking more than 0.5 g of xylitol per kg of body weight a laxative effect may occur, which may disappear after the adaptation of the organism. There were tolerated in studies revenue of 200 g of xylitol daily problems. When this adjustment is not sorbitol, sorbitol therefore always acts laxative.

In the large intestine, the remaining xylitol (about 2/3 of the occupied volume) divided by bacteria and fatty acid components into small degraded and absorbed. These are metabolized to carbon dioxide (CO2 ) and water.

Medical importance

Anti- cariogenic effect

Xylitol was discovered as a potential carbohydrate kariesreduzierendes the early 1970s. At the University of Turku ( Finland), in the years 1972 to 1975 two clinical trials (known as Turku sugar studies) carried out which have demonstrated a highly significant reduction of caries.

In the first two years of nutritional study sugar (sucrose) was replaced in all foods with fructose or xylitol. A total of 115 people in total 3 groups participated. The consumption of sweeteners amounted to 50 to 67 g per day. According to the study, a caries reduction of 30% fructose, and from about 85% with the use of xylitol could be determined. For comparison, the so-called DMFS index was used. The increase in the index was 7.2 in the sucrose group, 3.8 in the fructose group and 0.0 in the Xylitolgruppe.

The second study was started after a marked reduction in DMFS values ​​were observed in subjects during the first study, that is, that they had a so-called Kariesreversion, with certain caries lesions had undergone a Wiedererhärtungsprozess. Around 100 people were divided into sucrose and Xylitolgruppen. The sweetener was administered in the course of a year in chewing gum, about 7 grams per day per person. In comparison to the sucrose group, a reduction of caries growth rate by more than 82 % was determined in the Xylitolprobanden. The Kaueffekt could be excluded, as both groups consumed the same amount of gum. One conclusion of the study is that already enough small amounts of xylitol and a complete change of the sweetener is not necessary.

These effects are explained by the fact that the cariogenic bacteria of the genus Streptococcus mutans can not metabolize xylitol and thus die. Further, they are also prevented to attach as plaque bacteria on the tooth surface. The optimum xylitol portions were determined 5 to 10 grams per day in several. These can be recorded by means of gum or lozenges.

In addition, Xylitol stimulates saliva production and promotes the formation of complexes with calcium and saliva proteins in the oral cavity, resulting in remineralization of tooth structure.

In another study from Turku 2000, the interactions between mothers who chewed xylitol chewing gum regularly were, and (up to 2 years old ) were examined for their children. One result of the study was that the regular consumption of xylitol chewing gum by mothers significantly inhibit infection by Streptococcus mutans in children.

A double-blind study conducted in 2013 with 538 people who were given 5 grams of xylitol per day, however, no preventive effect against caries found in patients with an adequate fluoride intake.

Use in acute otitis media

In some studies, could be achieved with the administration of high doses of xylitol prophylactic effect regarding acute otitis media otitis media acuta. Xylitol inhibits the growth of pneumococci and the binding of pneumococci and Haemophilus influenzae to the cells in the nasopharynx. The Xylitoldosis ranged from 10 g / day.

Osteoporosis Preventive effect

In the intestine, xylitol forms complexes with calcium and facilitates its absorption. This could be a little -studied way to prevent osteoporosis.

Veterinary Importance

Xylitol has in some animal species (dogs, cattle, goats, rabbits ) can cause a strong insulin - distributing effect of a life-threatening drop in blood sugar levels (hypoglycemia ). In dogs, severe liver injury were observed in addition to liver failure and coagulation disorders. Even a dose of 0.1 g per kg body mass is toxic to the animal, a lethal dose is achieved at about 3-4 g xylitol per kg of body weight. Eating a bag of xylitol -containing candies can even be fatal for a big dog, when the animal is not as fast as possible in intensive care.

Mechanism and resistance

Xylitol affects Streptococcus mutans by two mechanisms:

Another suspected but not confirmed mechanism of action for the anti- cariogenic effect is that not all strains of S. mutans are sensitive to xylitol and therefore resistant strains can proliferate preferably at Xylitolverwendung. It is believed that these are less cariogenic.

However, the resistance effect is not so strong to bear as with antibiotics, because xylitol has an additional effect, namely the reduction of the biofilm, the mucus layer on the teeth and in the oral cavity, which is caused by lack of necessary carbohydrates and chewing gum use. This self- refer patients with resistant strains mainly to a reduced settlement.