Cyclodextrins starch

Szejtli, J. Sebestyen, G. Resorption, metabohsm and toxicity studies on the peroral application of P-cyclodextrin. Starch/Staerke 1979, 31 (11), 385-389. 

Szejtli, J, A Liptik and 1 Jodal (1980). Synthesis and 13C-NMR spectroscopy of methylated beta-cyclodextrins. Starch, 32(5), 165-169. 

Cyclodextrins are macrocyclic compounds comprised of D-glucose bonded through 1,4-a-linkages and produced enzymatically from starch. The greek letter which proceeds the name indicates the number of glucose units incorporated in the CD (eg, a = 6, /5 = 7, 7 = 8, etc). Cyclodextrins are toroidal shaped molecules with a relatively hydrophobic internal cavity (Fig. 6). The exterior is relatively hydrophilic because of the presence of the primary and secondary hydroxyls. The primary C-6 hydroxyls are free to rotate and can partially block the CD cavity from one end. The mouth of the opposite end of the CD cavity is encircled by the C-2 and C-3 secondary hydroxyls. The restricted conformational freedom and orientation of these secondary hydroxyls is thought to be responsible for the chiral recognition inherent in these molecules (77). 

Of particular importance for modifications of starch are the enzyme degradation products such as glucose symps, cyclodextrins, maltodextrins, and high fmctose com symps (HFCS). Production of such hydrolysis products requites use of selected starch-degrading enzymes such as a-amylase,... 

Low cholesterol egg products are formed by extraction of cholesterol from the egg. Attempts have been made to extract cholesterol by using hexane or by supercritical CO2 extraction methods (24,25). A whole egg product in which 80% of the cholesterol is removed by a process using beta-cyclodextrin, a starch derivative, added to egg yolks has been introduced. The cyclodextrin binds up to 80% of the cholesterol, the mixture is centrifuged, and the Hquid separated. The cholesterol-reduced yolk is then blended with egg white, pasteurized, and packed in asceptic containers to give a Hquid whole egg product having a shelf Hfe of 60 days under refrigeration (see Eood packaging). 

The cyclodextrins are produced by the partial degradation of starch followed by the enzymatic coupling of the glucose units into... 

Cyclodextrins (CDs) are inclusion compounds formed by enzymatic decomposition of starch to the cyclic oligosaccharides containing six to eight... 

Thus, despite all the work carried out on starch-iodine, the exact nature of the guest iodine atoms is still not totally resolved. Teitelbaum, Ruby and Marks 156) have examined the compound using Raman and 129I Mossbauer spectroscopy and concluded that the pentaiodide ion 1 was the major chromophore present. However work based on iodine compounds of cyclodextrins 3-134 135) has shown that a variety of polyiodide species is possible, and the starch-iodine inclusion compound could conceivably involve I2 If, I2 I- I2, or I5 species 157). The anhydrous amylose-iodine compound has recently been found to exhibit semiconductor behaviour 158). 

Figure 4.15 Selective adsorption synthesis of a-cyclodextrin from starch applying a hatch process using a sequence of stirred-tank reactor, heat exchanger modules and adsorption step...

Sucrase-type (non-Leloir-type) enzymes that operate both regio- and stereo-selectively, using sucrose as a cheap substrate, or, in some cases (such as cyclodextrin (CD) transferases) starch these enzymes are, however, limited to the transfer of only glucose or fructose... 

It should be noted that molecular complexes of the cyclodextrins may be isolated as crystalline solids for example, a crystalline complex is obtained with iodine (which resembles the well known blue complex between iodine and starch) as well as with a large number of other inorganic and organic guests. 

Lopez-Nicolas JM, Bru R and Garcia-Carmona F. 1997. Enzymatic oxidation of linoleic acid by lipoxygenase forming inclusion complexes with cyclodextrins as starch model molecules. J Agric Food Chem 45 1144-1148. 

These water-soluble molecules are cyclic oligomers of a-D-glucose formed by the action of certain bacterial amylases on starches (Bender and Komiyama, 1978 Saenger, 1980 Szejtli, 1982). a-Cyclodextrin (cyclohexa-amylose) has six glucose units joined a(l, 4) in a torus [1], whereas /3-cyclodextrin (cycloheptaamylose) and y-cyclodextrin (cyclooctaamylose) have seven and eight units, respectively. 

This starch derivative is a water-soluble polymer of D-glucose with a largely helical structure. Therefore, like cyclodextrins, it has the ability to bind alkyl chains and to catalyse reactions through the involvement of ionized hydroxyl groups in basic solution (Hui et al., 1982 Cheng et al., 1985). 

The first report in the literature of the isolation of a substance recognizable as a cyclodextrin was that of Villiers which appeared in 1891. From digests of Bacillus amylobacter on potato starch, Villiers obtained a small amount (3 g per 1000 g of starch) of a crystalline material, which he named cellulosine because of its resemblance in some respects to cellulose. The foundations of cyclodextrin chemistry were laid down, however, in the period 1903-1911 by Schardinger, and, in fact, some of the older literature frequently refers to the cyclodextrins as Schardinger dextrins. 

Since the time of Schardinger, one of the most important reasons for studying the cyclodextrins was for the information they might yield on the structure of starch and of the well known blue iodine-starch complex. In fact, the similarity between the iodine-starch reaction and the iodine-alpha cyclodextrin reaction was first noted by Schardinger in 1911, in his final paper on the cyclodextrins. 

Prior to 1939, however, it was not known whether the cyclodextrins were products of the synthetic metabolism of Bacillus macerans, and therefore, perhaps, quite different from the components of starch, or whether they were formed by a single enzyme and therefore closely related to the starch structure. Then, Tilden and Hudson announced the discovery of a cell-free enzyme preparation from cultures of Bacillus macerans which had the ability to convert starch into the Schardinger dextrins without the production of maltose, glucose, or any other reducing sugars. They thus concluded that the Schardinger dextrins were either the true components of starch or closely related to such true components. 

Thus, Freudenberg concluded that the cyclodextrins are not preformed in starch, but that their formation is made possible by the helicity of the starch chain. Freudenberg s hypotheses concerning the starch structure (that is, the amylose fraction) and the Bacillus macerans amylase mechanism have been confirmed by X-ray crystallography and chromatographic techniques. ... 

Among the best known and most versatile hosts are the various cydodextrins [1,2] of which a-, P- and y-cyclodextrins are the most available. These are cyclic oligosaccharides built up of six, seven, or eight glucopyranose units, respectively. These compounds can be prepared by enzymatic hydrolysis of starch. The undoubtedly most important member of the cyclodextrin family is P-cyclodextrin (P-CD) which has become a cheap and easily available chemical, suitable for large scale applications. Schemes... 

Mol. weight (xlO Optimum pH pH stability Optimum temp. Thermostability Isoelectric point Product from pullulan from starch Activator Inhibitor Cyclodextrin (B- and y-)... 

Cyclodextrins (CDs) were first observed by Villiers (i) nearly a century ago. First thought to be a mysterious crystalline form of starch, the structure and chemistry of these unique cyclic glucan oligosaccharides have been elucidated through the contributions of Schardinger, Freudenburg, Cramer and French (2). 

Starch Liquefaction with a Highly Thermostable Cyclodextrin Glycosyl Transferase from Thermoanaerobacter Species... 

During secondary liquefaction at 95 C or 90 C, a r id reduction in viscosity was observed. At 90 C, the viscosity reduction was monitored over time with a Nametre viscometer. The results demonstrated there was a r id reduction in viscosity to 400 centipoise x gm/cm by 7 minutes into secondary liquefaction (Figure 6). The action patterns of the liquefied starches following secondary liquefaction demonstrated the characteristic cyclodextrin action pattern at both temperatures. DE values were < 1.0 indicating the absence of reducing end-groups consistent with the mechanism of a CGTase. 

---