Starch carboxylic esters

Besides substances linked to a polymeric carrier by amide-like bonds, drugs with ester-like bonds cannot be split off. Thus, Kratzl and Kaufmann (77) have not detected any splitting or liberation of the nervous system attacking analepticum Ethamivan (Emivan , Vandid ) in the physiological system, if it is bound to starch through a carboxylic ester bridge which is very easily hydrolyzed in vitro (15). 

Starch complexes with aromas and flavoring agents are usually synthetic in origin. In nature, starch sometimes includes some aroma- and flavor-genic components that generate flavor and aroma on processing (see, for instance, ref. 678). Such agents include mainly aldehydes, ketones, and carboxylic esters however, hydrocarbons, alcohols, carboxylic acids, and haloalkanes have also been used. 

The class of compounds called polyesters consists of aU heterochain macromolecular compounds that possess repeat carboxylate ester groups in the backbones. This excludes all polymers with ester groups located as pendant groups, like acrylic and methacrylic polymers, poly(vinyl esters), and esters of cellulose, or starch. What remains, however, is still a large group of polymeric materials that can be subdivided into saturated and unsaturated polyesters. 

Starch acetates and some other carboxylate esters, symbolized by the introduction of R-CO-0-groups, are the most important organic esters. They are prepared by heterogeneous phase reaction of granular starch in slightly alkaline media (pH 8-8.5) at 15-25 °C with the respective acid anhydrides... 

Starch esters have been obtained by reactions of starch and carboxylic or sulfonic acid imidazolides in aqueous NaOH or nonaqueous solutions, as described in reference [226]. The esterification of dextran with butyric or palmitic acid using CDI in DMSO or formamide is discussed in reference [174]. 

Poly(vinyl alcohol) is utilized as a component of starch-based adhesives.11121114 Other patents report the use of partially oxidized starch,1115 dextrins,1116 dextrins and urea,1117 borax,1118 boric acid,1119 and vinyl methyl ether-maleic acid copolymers.1120 Other patents indicate the use of poly (vinyl alcohol) with partially hydrolyzed poly(vinyl acetate),1121 nonhy-drolyzed poly(vinyl acetate),1122 and poly(vinyl chloride).1123 A few patents have reported such poly acrylic additives as poly (acrylic acid)1124 and its salts,1125 poly(acrylamide),1126 1127 A-methylacrylamide or poly(A-acryl-amide),1128 and polyethyleneimine.1129 Polystyrene has also been used,1130 as well as more complex copolymers such as a maleic acid monobutyl ester-methyl vinyl ether copolymer, together with dextrin and polyacrylamide),1131 carboxylated ethyl acrylate-styrene zinc salt copolymer,1132 ethylene-methyl acrylate-vinyl acetate copolymer,1133 vinyl acetate-vinyl pyr-rolidone copolymer,1134 and ethylene-vinyl acetate copolymer.1135 Some adhesives are compounded with SBR latex1136 1138 and phenol-formaldehyde resins.1139... 

The mechanism of the action of beta-amylase involves interaction of the starch with imidazole and carboxyl groups of the enzyme, resulting in a glycosyl ester intermediate (fi form of the D-glucose residue) that is hydrolyzed by addition of water to the carboxyl group, thus releasing the maltose in the /3-anomeric configuration. 

As used in this chapter, a starch modification refers to starch molecules which have a general change in the polyglucan structure without the addition of a chemical sustituent. Examples include depolymerized starches and dextrins (including pyrodextrins and cycloamylases). Derivatized starches have had the addition of chemical groups at the hydroxyls. These include the starch ethers and esters. Oxidized starches can be both modified (when depolymerized) and derivatized (with carboxyl and carbonyl groups). 

National Starch Chemical UV radiation of hot melt comprised of at least one 3-(chlorinated aryloxy)-2-hydroxy-propyl ester of an alpha, beta unsaturated carboxylic acid with acrylate based copolymer izable monomers. PSA properties. 

The benzotriazolide of the succinic half-ester of starch was prepared by reaction with 1-H-benzotriazole in the presence of ci-cyclohexylcarbodiimide. The reaction yield was about 66%, i.e., only about two out of three carboxyl groups were transformed into benzotriazolide groups ... 

Starch esters are synthesized by reaction of a carboxylic acid or an acyl chloride or an acid anhydride with the hydroxyl groups of amylose or amylopectin chains. As in the case of cellulose derivatives, there are organic and inorganic esters depending on the origin of the substituent. 

FT-IR spectra (9) of pectin/starch/glycerol (P/S/G) films were taken to provide information concerning the microstructure around ester and carboxylic acid side chains in the backbone of pectin. Pectin, unlike starch and glycerol, exhibits infrared absorption bands in the regions near 1610 and 1740 cm For pectin dissolved in D2O, absorption bands occur at about 1730, 1740, and 1607 cm. These arise from the carboxylic acid C=0 stretching band, the methyl ester C=0 stretching band, and iht antisynunetric COO stretching band, respectively. The carboxylic acid band overlaps the ester band sufficiently that these appear as one broad band (22). 

Polysaccharides with strongly acidic residues, present as esters along the polymer chains (sulfuric, phosphoric acids, as in furcellaran, carrageenan or modified starch), are also very soluble in water and form highly viscous solutions. Unlike polysaccharides with carboxyl groups, in strongly acidic media these solutions are distinctly stable. 

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