Bruce L. May

Apple pomace, a by-product of juice production, is a high-fibre, high-polyphenol functional food ingredient. Extrusion (barrel moisture 15%, 20% or 30%) of apple pomace, followed by drying, allows it to be supplied in a convenient form. Extrusion caused degradation of the apple pomace cell wall structure. Water solubility was significantly increased by extrusion but oil holding capacity was reduced. Total extractable polyphenols, measured as gallic acid equivalents, were reduced by extrusion (barrel moisture 30%) but were not affected by extrusion at lower barrel moisture contents (15% or 20%). However, individual sub-groups of extractable flavanols, flavonols, phenolic acids and dihydrochalcones were increased by extrusion. There was little effect of extrusion on the release of total polyphenols from the matrix into the supernatant, as measured by total extractable polyphenols (measured as gallic acid equivalents) released during in vitro digestion. There was a marked increase in total flavanols, phenolic acids and dihydrochalones released into the supernatant during the gastric phase but changes in flavonoids were less obvious. The changes in the bioaccessibility of individual polyphenols released during intestinal digestion were dependent on the type of polyphenol and extrusion conditions. The antioxidant activity, as measured using oxygen radical absorbance capacity (ORAC) of the bioaccessible nutrients released upon in vitro intestinal digestion, was significantly enhanced by extrusion (from 78.2 to 400–500 μmol Trolox equivalents per mL at the ileal phase). The increased ORAC may be attributed in part to the increased release of individual polyphenols.

The preparation of the Zn2+ specific fluorophore 2-((E)-2-phenyl)ethenyl-8-(N-4-methylbenzene-sulfonyl)aminoquinol-6-yloxyacetic acid, H23, is described. The protonated form, H33+, is characterized by pKa values of 2.71 ± 0.03, 4.92 ± 0.03, and 10.46 ± 0.03 in 25% (v/v) aqueous ethanol 0.10 mol L–1 in NaClO4 at 298.2 K determined by potentiometric titration. At pH 6.6, but otherwise under the same conditions, the dianion, 32–, forms the fluorescent complexes [Zn(3)] and [Zn(3)2]2–, characterized by log(K1/L mol–1) = 10.5 ± 0.20 and log(K2/L mol–1) = 11.1 ± 0.1, respectively, as determined by fluorimetry. These data are compared with analogous data for the structurally similar and widely used fluorophore 2-methyl-8-p-toluenesulfonamido-6-quinolyloxyacetic acid (Zinquin A).

A ¹H NMR and rheological study of host‐guest complexation interactions between three β‐cyclodextrin and three adamantyl substituted poly(acrylate)s, and also between them and adamantan‐1‐carboxylate and native β‐cyclodextrin, respectively, is reported. A close correllation between molecular level interactions and macroscopic characteristics of polymer networks in aqueous solution exists. It is found that intra‐ and intermolecular host‐guest complexation between the host β‐cyclodextrin and guest adamantyl substituents and the length of the aliphatic tether between them and the poly(acrylate) backbone have important roles. Dominantly, steric effects and competitive intra‐ and intermolecular host‐guest complexation are found to control poly(acrylate) isomeric interstrand linkage in polymer network formation. The preparations of five new 3% randomly substituted poly(acrylate)s are reported. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1818–1825, 2010

A close correllation between molecular-level interactions and macroscopic characteristics of polymer networks exists. The characteristics of the polymeric hydrogels assembled from β-cyclodextrin (β-CD) and adamantyl (AD) substituted poly(acrylate)s can be tailored through selective host–guest complexation between β-CD and AD substituents and their tethers. Dominantly, steric effects and competitive intra- and intermolecular host–guest complexation are found to control poly(acrylate) isomeric inter-strand linkage in polymer network formation. This understanding of the factors involved in polymeric hydrogel formation points the way towards the construction of increasingly sophisticated biocompatible materials.

This study shows that stereochemical factors largely determine the extent to which 6-(4′-t-butylphenylamino)-naphthalene-2-sulphonate, BNS⁻  and its dimer, (BNS⁻ )₂, are complexed by β-cyclodextrin, βCD, and a range of linked βCD dimers. Fluorescence and ¹H NMR studies, respectively, show that BNS⁻  and (BNS⁻ )₂ form host–guest complexes with βCD of the stoichiometry βCD.BNS⁻  (10^− 4 K ₁ = 4.67 dm³ mol^− 1) and βCD.BNS₂ ^2 −  (10^− 2 K ₂′ = 2.31 dm³ mol^− 1), where the complexation constant K ₁ = [βCD.BNS⁻ ]/([βCD][BNS⁻ ]) and K ₂′ = [βCD. (BNS⁻ )₂]/([βCD.BNS⁻ ][BNS⁻ ]) in aqueous phosphate buffer at pH 7.0, I = 0.10 mol dm³ at 298.2 K. (The dimerisation of BNS⁻  is characterised by 10^− 2 K _d = 2.65 dm³ mol^− 1.) For N,N-bis((2^AS,3^AS)-3^A-deoxy-3^A-β-cyclodextrin)succinamide, 33βCD₂su, N-((2^AS,3^AS)-3^A-deoxy-3^A-β-cyclodextrin)-N′-(6^A-deoxy-6^A-β-cyclodextrin)urea, 36βCD₂su, N,N-bis(6^A-deoxy-6^A-β-cyclodextrin)succinamide, 66βCD₂su, N-((2^AS,3^AS)-3^A-deoxy-3^A-β-cyclodextrin)-N′-(6^A-deoxy-6^A-β-cyclodextrin)urea, 36βCD₂ur, and N,N-bis(6^A-deoxy-6^A-β-cyclodextrin)urea, 66βCD₂ur, the analogous 10^− 4 K ₁ = 11.0, 101, 330, 29.6 and 435 dm³ mol^− 1 and 10^− 2 K ₂′ = 2.56, 2.31, 2.59, 1.82 and 1.72 dm³ mol^− 1, respectively. A similar variation occurs in K ₁ derived by UV–vis methods. The factors causing the variations in K ₁ and K ₂ are discussed in conjunction with ¹H ROESY NMR and molecular modelling studies.