Gentiobiose structure

Two cell-wall fractions were obtained from mycelia of Neurospora crassa by differential extraction with alkali (soluble in 4%, and insoluble in 24%) on incubation with endo-(l - 3)-/3-D-glucanase, both gave473 D-glucose, laminara-biose and -triose, and 62-/3-D-glucosyllaminarabiose (118). exo-(1 - 3)-/3-D-Glucanase released D-glucose and gentiobiose. Structures were proposed for both fractions when this evidence and the results of methylation analysis were considered. 

With three linkage bonds as in the molecular mechanics study of the 1-6 disaccharide gentiobiose (12), the lowest 24 minima within 7 kcal mole which were reported did not include that observed in the crystal structure (20). Had the crystal structure conformation been one of the sets of starting parameters, it would have been included, but it is reasonable to assume that the conformational population in solution was also not fully represented. 

Figure 2. Schematic diagram of the hydrogen-bond structure in the crystal structure of gentiobiose (GENTOSOl REFCODE in Cambridge Crystallographic Data Base). The arrows indicate infinite chains. Distances are H—O in A, angles are 0-H—O in degrees. The covalent 0-H bond lengths have been normalized to 0.97 A.

A short presentation of the Consistent Force Field is given, with emphasis on parametrization and optimization of energy function parameters. For best possible calculation of structure, potential energy functions with parameter values optimized on both structural and other properties must be used. Results from optimization with the Consistent Force Field on alkanes and ethers are applied to glucose, gentiobiose, maltose and cellobiose. Comparison is made with earlier and with parallel work. The meaning and use of conformational maps is discussed shortly. 

Saffron extract contains many carotenoids such as crocetin, crocetin di-glucose ester, crocetin gentiobiose glucose ester, and crocin (crocetin di-gentiobiose ester), whose chemical structures are shown in Figure 58.1. These carotenoids scavenge free radicals, especially superoxide anions, and so may protect cells from oxidative stress. Indeed, it has been demonstrated that these carotenoids are useful in sperm cryoconservation and in protecting heptocytes from toxins. 

FIGURE 58.1 Chemical structures of crocetin (A), crocetin diglucose ester (B), crocetin gentiobiose glucose ester (C), and crocin (D). 

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