Use of a modified cyclodextrin host for the enantioselective detection of a halogenated diether as chiral guest via optical and electrical transducers

In an alkaline rebreathing circuit, the inhalation anesthetic sevoflurane degrades into at least two products, one of them being the chiral halodiether 1,1,1,3,3-pentafluoro-2-(fluoromethoxy)-3-methoxypropane (halodiether B). Using octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-y-cyclodextrin (Lipodex E) as chiral host diluted in the polysiloxane PS255, an exceptional large chiral separation factor alpha of 9.7 at 30 degrees C was found for halodiether B by capillary gas chromatography (cGC). Hence, the interaction of the single enantiomers and the racemic mixture of the halodiether B with Lipodex E was selected as a model system to study the enantioselective recognition by thickness shear mode resonators (TSMR), surface acoustic wave sensors, surface plasmon resonance (SPR), and reflectometric interference spectroscopy. Further investigations of the recognition process by using chemical sensors confirmed the preferential enrichment of the S-enantiomer resulting in 9-fold higher signals. Based on the distinction between enantioselective and nonenantioselective sorption, thermodynamic complexation constants of the single enantiomers with Lipodex E could be determined. The difference in Gibbs free energy -deltaE2,E1(deltaG) of the complexation of the enantiomers of halodiether B with pure Lipodex E was determined at 30 degrees C by TSMR and SPR to be 5.7 or 5.9 kJ/mol, respectively, agreeing well with that determined by cGC, i.e., 5.7 kJ/mol at 30 degrees C.     

Gut health benefits of kiwifruit pectins: Comparison with commercial functional polysaccharides

The role of kiwifruit pectin as a functional food ingredient capable of beneficial gut health effects in vitro was investigated. Six different pectins were obtained from the kiwifruit cultivar Actinidia deliciosa ‘Hayward’ (ZESPRI? GREEN) by selective re-solubilisation of the fruit fibre with different chemical treatments. The potential gut health benefit of kiwifruit pectin was tested with respect to its influence on bacterial adhesion to intestinal epithelial cells (Caco-2) in vitro. The most effective kiwifruit pectin (monoK pectin), obtained by re-solubilisation with monopotassium phosphate, was compared with three commercial functional polysaccharides - citrus pectin, guar gum and inulin. The monoK pectin was superior to inulin, a standard prebiotic in enhancing the adhesion of Lactobacillus rhamnosus and decreasing the adhesion of Salmonella typhimurium to Caco-2 cells. The adhesion of Bifidobacterium bifidum was significantly enhanced only by inulin and citrus pectin, while guar gum had no effect on adhesion of any of these bacteria.