Hexopyranosyl-(1->6)hexopyranosyl-(1->6)hexose

DescriptionDextran, a glucose polymer composed predominantly of ol-1,6-glucopyranosidic linkages, is produced from sucrose by Leuconostoc mesenteroides and related organisms and from dextrins by other bacteria. Dextran is used in a bead form to aid in bioreactor applications, some size-exclusion chromatography matrices and in osmotic stress technique study involved in biological molecules. It can be used as a stabilizing coating to protect metal nanoparticles from oxidation. Dextrans are long-chain glucose polysaccharides of various relative molecular masses. Dextran 70 (relative molecular mass 70 000) is retained in the intravascular space where, like albumin, it contributes to the colloid oncotic pressure of plasma. Unlike albumin, dextran 70, when given in large amounts, prevents platelet aggregation and facilitates fibrinolysis.

HistoryIn the early 1940's, at the same time as Stacey and his associates in Birmingham were studying bacterial dextrans and Hehre and colleagues in the USA were pursuing the dextran producing activity of cell-free extracts of Leuconostoc , a young Swedish biochemist, B. Ingelman, at the Department of Biochemistry and Physical Chemistry, University of Uppsala began probing the polysaccharides and proteins of sugar beet juice. One of the critical episodes was the discovery of dextran in an infected sample of the juice. This initiated a series of investigations on the polysaccharide. At the end of 1942, a recently qualified M.D., A. Grönwall, joined the laboratory to study tuberculin. Considerable effort was being devoted at the time to the freeze-drying of blood plasma for military medicine. Within the space of months, Ingelman and Grönwall had stumbled on the idea of using a hydrolyzed dextran as a plasma substitute. After studies on the partial hydrolysis, fractionation, and extensive biological studies, a Swedish pharmaceutical company adopted the project in 1943, and later that year, preliminary clinical trials began. In 1944, under the direction of the surgeon, G. Bohmansson, extensive clinical trials were started at the Regional Hospital in Örebro. The dextran used at that time was derived from Leuconostoc mesenteroides , strain 7E, and was slightly more branched than the present one. By 1947, about four years after the innovation, a 6% solution of a dextran fraction had been approved for clinical use in Sweden and, shortly thereafter, in the U.K., an achievement that would be inconceivable under the present regulatory climate.The product was gradually improved and was designated Dextran 70. Samples of the Swedish product were soon tested clinically in the USA. Dextran 70 is generally marketed as a 6% solution in normal saline and as such continues to maintain its position worldwide as the plasma volume expander of choice. It is recommended for the treatment of shock or impending shock due, for example, to hemorrhage, burns, surgery or trauma. Dextran 70 also reduces the risk for thrombosis and numerous studies testify to its value in significantly reducing the risk of post-operative fatal pulmonary emboli.

UsesThe demand for technical dextrans from industry has shown a significant increase in the past decade. Since household sucrose, fruits or fruit beverages could be contaminated with traces of dextrans, ingestion of dextrans, albeit in small amounts, may not be uncommon. Dextran is degraded by dextran-splitting bacteria in the human gut and most of the hydrolysis products can be absorbed to produce a rapid increase in blood sugar and liver glycogen However, in the food industry, where innumerable applications of dextrans in foodstuffs were patented in the 50's and 60's, no application appears to have been pursued and the mandatory toxicological studies to gain FDA approval were not performed. Hence in 1977, the GRAS (generally recognized as safe) status of dextrans was deleted. Dextrans are not permitted in the UK or Europe as foodstuff additives, and dextrans do not seem to have been considered by the Joint FAO/WHO Expert Committee on Foodstuff Additives (JECFA). Dextrans are, however, considered as safe as components of food packaging materials. Dextran fractions do not appear to be included in the lists of permitted additives (ingredients) for pharmaceutical formulations such as ointments and creams for topical use and tablets and capsules for oral use. However, providing the appropriate documentation is presented, there are no a priori reasons why they may not be used. Indeed several products in which a dextran fraction is used as a non-active ingredient are on the market. Purified dextran fractions with high clarity and low chloride levels find extensive applications in the photographic industry. Addition of low concentrations of dextran to the silver emulsion is found to enhance significantly the quality of the images. The effect is presumably attributable to the effect of dextran on the conformation of the gelatin molecules. Since Albertsson revealed the enormous potential of 2-phase polymer systems, especially dextran-PEG systems, for the partition of sub-cellular particles and macromolecules, an immense number of applications has evolved. These systems offer a means of fractionation beyond the range of conventional techniques. Some recent applications are: the separation of peripheral blood cells, distinguishing erythrocytes from multiple sclerosis patients, the separation of enzymes, for example pullulanase, from Klebsiella pneumoniae cells, and the partitioning of murine lymphoblasts. Dextran has been recommended as a cryoprotective agent for human, animal and plant cells. Thus a mixture of 5% methyl sulphoxide and 9% Dextran 70 was found to afford optimal cryoprotection of human bone marrow committed stem cells. The effect of dextrans as adjuvants for prolonging local anesthetic block has been a matter of some debate. Early results had proved somewhat contradictory. Recent reexamination by

DescriptionDextrans are glucose polymers produced by bacteria linked in an α-1,6 chain and having an α-1,3 or α-1,4 branch about every fifth residue. The specific positioning of the branching varies by the bacterium producing it. The molecular weights of these chains generally are 40 or 70 kDa (dextran-40 and dextran-70, respectively), and the compounds work via an osmotic gradient similar to the colloids and hypertonic crystalloid solutions. Dextrans have a longer intravascular residence time than albumin, which limits interstitial edema. As with the crystalloids and other colloids, the dextrans have no oxygen-carrying capacity. Furthermore, because they are bacterial products, the dextrans have the potential to be potent antigens and induce anaphylaxis.

Usesexhibit borad spectrum of biological activities, with very low anticoagulant capacity: they activate lipoprotein elimination by lipase stimulation, inhibit cell proliferation in vascular wall, regulate transport of plasmatic proteins and inhibit depositi

UsesDextran is a polysaccharide composed of glucose molecules used as an antithrombotic to reduce blood viscosity and as a volume expander in anemia. Studies show that it inhibits the mannose receptor-med iated clearance of tissue-type plasminogen activator (t-PA).

Usesalso available in pharma grade

Usesantiinflammatory veterinary drug

Usesdextran is a polysaccharide with water-binding properties. It is also used to control product viscosity. Some studies indicate a capacity to enhance the anti-aging activity of formulations containing weak acids, as well as to reduce possible skin irritation arising from such acids.

General DescriptionDextrans are polysaccharides with molecular weights ≥1,000 Dalton, with a linear backbone of α-linked D-glucopyranosyl repeating units. Dextrans are found as bacterial extracellular polysaccharides. They are synthesized from sucrose by Leuconostoc mesenteroides and Lactobacillus brevis. Bacteria employ dextran in biofilm formation or as a protective coating to evade host phagocytes in the case of pathogenic bacteria.Dextran from Leuconostoc mesenteroides (Mw: 12,000) may be used as an analytical standard to calibrate the column for gel permeation chromatography (GPC).

Definitiondextran: A glutinous glucose polymerproduced by certain bacteria. Itcan be made by fermenting sucrose(cane sugar) and is used as a thickeningagent, as a stabilizer in ice cream,and as a substitute for plasma inblood transfusions. Esters with sulphuricacid yield sodium salts thatare employed as anticoagulant drugs.