2.1.6 Dextran
Dextran is a carbohydrate substance made up predominantly of D-glucose units i.e. (C6H10O5)n. It is α–1, 6 linked polyglucan.
Synonyms Dextraven; Expandex; Gentran;Hemodex; Intradex; Macrose; Onkotin; Plavolex; Polyglucin.
Biological Source A number of organisms produce dextrans; however, only two of them, namely; Leuconostoc mesenteroides and L. dextranicum, belonging to the family Lactobacteriaceae, have been used commercially.
Preparation Commercially, dextrans are manufactured by the process of fermentation of sucrose (a disaccharide) either by cell-free enzymatic fermentation technique or by whole culture technique. The enzymes that are responsible for producing dextrans from sucrose as a substrate are collectively known as ‘dextran-sucrases’.
Native dextran possesses a very high moleculer weight, whereas the clinical dextrans have lower moleculer weights, for instane; Dextran 40 [Gentran 40(R) (Baxter); Rheomacrodex(R) (Pharmacia)]; Dextran 70 [Hyskon(R) & Macrodex(R) (Kabi Pharmacia)]; Dextran 75 [Gentran 75(R) (Baxter)]; These may be accomplished by controlled depolymerization e.g., ultrasonic vibration, fungal dextranase and acid hydrolysis.
Description Dextrans obtained by the precipitation from methanol vary considerably with regard to their characteristic physical and chemical properties which solely depends upon the individual method of preparation.
Chemical Constituents The interaction between ‘n’ molecules of sucrose and ‘x’ number of glucose moieties yields dextran together with ‘n’ molecules of fructose as shown in the following equation:
nSucrose + (Glucose)x → (Glucose)x+n + nFructose
Primer Dextran
Uses
1. Dextran 40 is employed as an isotonic solution either to prime pumps or to improve flow in surgery concerned with cardiopulmonary bypass. Thus, it exerts its effect by lowering the viscosity of blood and improving flow; and the latter is caused due to hemodilution.
2. Dextrans as a whole helps in minimising platelet adhesiveness, which property is gainfully exploited in their usage for prophylaxis of thrombosis and thromoembolism both during and after surgery.
3. Both Dextran 70 and Dextran 75 find their extensive use as plasma extender for the control and management of hypovolemic shock. Hypertonic solutions usually afford the dehydration of tissues, whereby the abstracted water being added to the plasma causing increase in its volume. For this reason they are quite useful in the prevention and treatment of toxemia of pregnancy and nephrosis.
4. Dextran 70 and Dextran 75 are used in 6% solutions to prevent pending shock caused by hemorrhage, trauma, and severe burns.
5. Dextran 40 (10% solution) is not only used to lower blood viscosity but also to improve microcirculation at low flow rates.
6. Dextrans are employed in the formulation of fat-soluble vitamins (viz. Vitamin A, D, E, K).
7. It is also used in preparing sustained released tablets.
8. Dextrans find their abundant applications in various types of confectionaries, for instance: icecreams, candies, jellies, syrups and cake–topings.
9. It is employed as an adjunct in cosmetic preparation exclusively meant for soothening wrinkles.
