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| Identifiers | |
|---|---|
| ChemSpider |
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| ECHA InfoCard | 100.029.694 |
| KEGG |
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| UNII | |
| Properties | |
| H(C6H10O5)xOH | |
| Molar mass | Variable |
| Pharmacology | |
| B05AA05 (WHO) | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Dextran is a complex branchedglucan (polysaccharide derived from the condensation ofglucose), originally derived fromwine.IUPAC defines dextrans as "Branched poly-α-d-glucosides of microbial origin having glycosidic bonds predominantly C-1 → C-6".[1] Dextran chains are of varying lengths (from 3 to 2000kilodaltons).
The polymer main chain consists of α-1,6glycosidic linkages between glucose monomers, with branches from α-1,3 linkages. This characteristic branching distinguishes a dextran from adextrin, which is a straight chain glucose polymer tethered by α-1,4 or α-1,6 linkages.[2]
Dextran was discovered byLouis Pasteur as a microbial product in wine,[3] but mass production was only possible after the development byAllene Jeanes of a process usingbacteria.[4]Dental plaque is rich in dextrans.[5] Dextran is a complicating contaminant in the refining of sugar because it elevates the viscosity ofsucrose solutions and fouls plumbing.[6]
Dextran is now produced from sucrose by certainlactic acid bacteria of the family lactobacillus. Species includeLeuconostoc mesenteroides andStreptococcus mutans. The structure of dextran produced depends not only on the family and species of the bacterium but on the strain. They are separated by fractional precipitation from protein-free extracts usingethanol. Some bacteria coproducefructans, which can complicate isolation of the dextrans.[6]
Dextran 70 is on theWHO Model List of Essential Medicines, the most important medications needed in ahealth system.[7]
Medicinally it is used as anantithrombotic (antiplatelet), to reduce bloodviscosity, and as a volume expander inhypovolaemia.[8]
These agents are used commonly by microsurgeons to decrease vascularthrombosis. The antithrombotic effect of dextran is mediated through its binding oferythrocytes,platelets, and vascularendothelium, increasing theirelectronegativity and thus reducingerythrocyte aggregation andplatelet adhesiveness. Dextrans also reduce factor VIII-AgVon Willebrand factor, thereby decreasing platelet function. Clots formed after administration of dextrans are more easily lysed due to an altered thrombus structure (more evenly distributed platelets with coarserfibrin[citation needed]). By inhibiting α-2 antiplasmin, dextran serves as aplasminogen activator, so possessesthrombolytic features.
Outside of these features, larger dextrans, which do not pass out of the vessels, are potent osmotic agents, thus have been used urgently to treathypovolemia[citation needed]. The hemodilution caused by volume expansion with dextran use improves blood flow, thus further improving patency of microanastomoses and reducing thrombosis. Still, no difference has been detected in antithrombotic effectiveness in comparison of intra-arterial and intravenous administration of dextran.
Dextrans are available in multiple molecular weights ranging from 3 kDa to 2 MDa. The larger dextrans (>60,000 Da) are excreted poorly from the kidney, so remain in the blood for as long as weeks until they are metabolized. Consequently, they have prolonged antithrombotic andcolloidal effects. In this family, dextran-40 (MW: 40,000 Da), has been the most popular member foranticoagulation therapy. Close to 70% of dextran-40 is excreted in urine within the first 24 hours after intravenous infusion, while the remaining 30% are retained for several more days.
Although relatively few side effects are associated with dextran use, these side effects can be very serious. These includeanaphylaxis,[14] volume overload,pulmonary edema,cerebral edema, or platelet dysfunction.
An uncommon but significant complication of dextran osmotic effect isacute kidney injury.[15] The pathogenesis of this kidney failure is the subject of many debates with direct toxic effect on tubules andglomerulus versus intraluminal hyperviscosity being some of the proposed mechanisms.[citation needed] Patients with history ofdiabetes mellitus,chronic kidney disease, or vascular disorders are most at risk. Brooks and others recommend the avoidance of dextran therapy in patients with chronic kidney disease.
Efforts have been made to develop modified dextran polymers. One of these hasacetal modifiedhydroxyl groups. It isinsoluble in water, but soluble in organicsolvents. This allows it to be processed in the same manner as manypolyesters, likepoly(lactic-co-glycolic acid), through processes like solvent evaporation andemulsion.Acetalated dextran is structurally different fromacetylated dextran. As of 2017 several uses fordrug delivery had been exploredin vitro and a few had been tested in animal models.[16]
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