Raffinose crystallization

Raffinose crystallizes from water, or from aqueous alcohols or acetic acid, as the pentahydrate, of m.p. 78°, [a]20D + 105.2° (c 4, in water). No crystalline, characterizing derivatives of raffinose are known. Raffinose may be exactly identified by comparison of its x-ray diffraction powder pattern with that of an authentic standard.28 Other information of value in the identification of raffinose is its extreme ease of acid hydrolysis... 

Figure 2 Micrographs of a raffinose crystal (left), showing pronounced birefringence, and the same crystal (right) after dehydration by vacuum treatment at room temperature. The ultrastructure resembles that of the crystal, but the absence of birefringence is evidence of the amorphous state from Kajiwara and Echlin, Pafra Biopreservation, unpublished...

Hungerford (51) determined the solubility in water from 0 to 78". At temperatures below 78° raffinose crystallizes from water with 5 moles of water of crystallization. This hydrate melts at 78.0 0.05°. Solubilities are expressed as the anhydride although the determinations were made on the pentahydrate ... 

D-galactose, C HiiOe. Crystallizes in the pyranose form m.p. 1I8-120 C (monohydrate), 165-5" C (anhydrous). An isomer of glucose which is fairly widely distributed in plants. It is a constituent of raffinose and slachyose, of hemicelluloses, of pectin, of gums and mucilages, and of some glycosides. In animals it forms half the lactose molecule and is the sugar found in the brain. Chemically it is very similar to glucose. It has the structure... 

F. Alberto, E. Jordi, B. Henrissat, and M. Czjzek, Crystal structure of inactivated Thermotoga maritima invertase in complex with the trisaccharide substrate raffinose, Biochem. J., 395 (2006) 4574-62. 

Figure 19. Packing arrangement of sucrose delineated by the observed crystal faces, as viewed along the c axis. The emerging galactose moiety of a raffinose inhibitor molecule has been inserted at the (110) face in the exo conformation. Note that the corresponding hydroxyl of sucrose adopts an endo conformation. The sugar ring inserted at the (lTO) face indicates the position that would be taken by the galactose moiety of a raffinose inhibitor molecule in the endo conformation.

Smythe (72) observed that the trisaccharide 1-kestose (7a), which bears an additional fructose moiety bound to Cl, binds at the —b pole of the crystal of sucrose. This result implies an extended antiplanar conformation (7b) of the group Cl -C-O-C(fiructose) such that the O-C(fructose) bond (filled circles in 7b) of the additive would point toward - b, away from the crystal interior. Note that, as in the sucrose-raffinose system, the Cl -C-O-H group of sucrose 5b (filled circles) adopts a gauche conformation with the C-OH bond pointing in the +b direction. It is gratifying that the necessary extended conformation of Cl -C-O-C was later demonstrated in an X-ray crystallographic study of 1-kestose 7b (74). 

Figure 5. Morphology of sucrose crystal grown in pure solution (b) and in the presence of raffinose (a) 100 projection.

Considering these problems, we tested a computer extrapolation (6) for sucrose, shown in the conformation maps in Figure 4. Four sets of crystal parameters were used, those from the structure of sucrose (S) (45) and those from the sucrose component of raffinose pentahydrate... 

Table 1.6.1 Glass transition temperature Tg and crystallization temperature Tc for amorphous sucrose, trehalose, lactose, raffinose and amorphous sucrose in the presence of absorbed water...

Crystallization of raffinose from Eucalyptus manna Johnston 1843 i... 

Ditto ( melitose ) Crystallization of raffinose from beet-sugar molasses and Berthelot 1856 2... 

Improves yield of sucrose from beet molasses by eliminating raffinose interference in crystallization of sucrose... 

Sucrose crystallizes from aqueous solutions as monoclinic, hemimor-phic crystals. The presence of raffinose or dextran impurities, if present in quantity, produces long needle-like shapes. 

Only one tri-saccharose is important. It is known as raffinose and has the composition Ci8H320]6. It is found in beets and is present in the molasses after the sucrose sugar is crystallized out. It is also found in barley and in cotton seeds. When this tri-saccharose hydrolyzes it yields first a di-saccharose known as melibiose and a monosaccharose fructose. The di-saccharose is then further hydrolyzed and yields two molecules of mono-saccharose, viz., glucose and galactose. The complete hydrolysis of the tri-saccharose, therefore, is as follows. 

Many drugs and excipients (cephalexin monohydrate, quinidine sulfate dihydrate, ampicillin trihydrate, codeine sulfate trihydrate, morphine sulfate dihydrate, dicalcium phosphate trihydrate, raffinose pentahy-drate, lactose monohydrate) utilize water as an integral part of their crystal structure. Solids that form specific crystal hydrates tend to sorb relatively small amounts of water to their external surface below a characteristic relative humidity, when initially dried to an anhydrous... 

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