Starch, /3-amylase action oxidation

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). 

D-Glucose and malto-oligosaccharides (DP 9) in starch hydrolysates have been separated by h.p.l.c. Oxidized (sodium hypochlorite) starch has been degraded by the joint actions of amyloglucosidase and a- and 3-amylases. An unidentified, modified trisaccharide, which resisted further enzymic degradation, was isolated. 

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