Hydroxyethyl starch, preparation

In Europe, several hydroxyethyl starch preparations are available commercially. Pentastarch, one of the more commonly used preparations, has been... 

Since granulocytes prepared by centrifugation are markedly contaminated with erythrocytes, the ABO compatibility between donor and recipient will be important unless the erythrocytes can be removed before use. Some reactions, particularly allergic and febrile complications, are associated with the presence of macromolecular agents (hydroxyethyl starch, modified gelatin, dextran), used to increase the yield of centrifugal techniques. ABO incompatibility does not alter the in vivo fate of granulocytes (39). 

Jiang G, Qin W, DeLnca P P (2003). Preparation and in vitro/in vivo evaluation of insnlin-loaded poly(acryloyl-hydroxyethyl starch)-PLGA composite microspheres. Pharm. Res. 20 452-459. 

For these and a variety of special non-food purposes esters with higher fatty acids, succinic, adipic and citric acids and carbamates (reaction products with urea), have also been prepared. Examples of starch ethers are 2-hydroxyethyl and 2-hydroxypropyl starches prepared by reaction of starch with oxirane (ethylene oxide) and methyloxirane (propylene-l,2-oxide). The reaction occurs preferentially at the secondary hydroxyl groups at C-2, with less on the C-3 and C-6 hydroxyl groups. The most common products are those shown in Figure 4.15. The degree of substitution tends to be <0.2. According to the reaction conditions, polyoxaalkyl starches ... 

Hydroxylall l Starch Ethers. Starch hydroxyethyl ethers with a degree of substitution (DS) of 0.05—0.10 ate produced in various ways, but usually their preparation begins at the end of the wet-milling process, utilizing a high soHds-starch suspension. The ether modification of ungelatinized starch is filterable and can be produced economically in a pure form. 

Phosphates are also known that have the phosphoric acid moiety in a side chain bound to glucose units. Such compounds have been prepared from diethyl 2-chloro-l-hydroxyethyl phosphonate [ClCH2CH(OH)PO(OEt)2].1585 The starch phosphonate ethers had a DS of 0.0138. In addition, 2-methyl-3-phosphono-2-oxazolinium chloride sodium salt was reacted with starch to produce stable, aqueous dispersions.1586... 

Like cellulose and starch, locust bean gum is able to form derivatives through reaction of the hydroxyl groups. The methyl ether has been prepared for constitutional work. For the time being only the water-soluble derivatives (hydroxyethyl and carboxymethyl ether) are of practical interest. They are used as alkali-resistant printing thickeners. 

The methods of g.l.c. have also been extended to 2-hydroxyethyl, 2-aminoethyl, and similar ethers. Such compounds have usually been encountered in work concerned with the preparation of modified starch or cellulose. These types of compound have litde direct bearing on the theme of the present article and will therefore not be discussed in detail, but representative applications are given in Table XXX (see p. 102). 

Methyl-, hydroxyethyl-, hydroxypropyl-, and carboxymethyl starches, starch acetates, succinates, alkenyl succinates (Fig. 2), adipates, and phosphates, are all well-known products. Furthermore, special derivatives have also been prepared, such as vinyl-, silyl-, ° or propargyl starches, as reactive intermediates for fiirther fime-tionalization. Unusual substitution patterns can also be established by highly selective deacetylation with alkyldiamines and subsequent introduction of such functional groups as sulfates. From die analytical point of view, the most important aspects are stability under alkaline (mediylation) and acidic or Lewis-acidic (depolymerization) conditions, reactivity (such as migration, rearrangement, further substitution or addition reactions, or any intramolecular reaction), and polarity (lipophilic/hydrophilic, ionic/nonionic, acidic/basic). These properties mainly determine the analytical... 

Hydroxyethylstarch (HES) is prepared from the amylopectin of waxy maize starch by hydrolysis and subsequent treatment with ethylene oxide. Amylopectin is a branched polyglucose composed of chains of a 1-4 linked glucose residues, to which a number of branches are attached by a 1-6 linkages (Aspinall 1970). When soluble amylopectin is intravenously injected into animals, it is rapidly degraded by a-amylase and is therefore unsuitable as a plasma substitute. For this reason Wiedersheim (1957) suggested substitution of amylopectin with hydroxyethyl groups to slow down the action of amylase and so extend its persistence in the circulation. He showed that such HES preparations had useful properties as plasma expanders and were relatively nontoxic. These results were subsequently confirmed and extended (Thompson et al. 1962, 1964, 1970). 

---