Antioxidant effects of chlorophyll and pheophytin on the autoxidation of oils in the dark. I. Comparison of the inhibitory effects

The effects of chlorophyll and pheophytin on the autoxidation of oils in the dark were investigated by oven tests. The results indicated that both chlorophyll and pheophytin show antioxidant activity when methyl linoleate is used as substrate. Furthermore, chlorophyll retarded the oxidative deterioration of triglycerides in rapeseed and soybean oils at 30 C. Among the four chlorophyll derivatives (chlorophylls a and b and pheophytins a and b), chlorophyll a showed the strongest antioxidant activity. The antioxidant effects of chlorophyll and pheophytin depended on the storage temperature and the kinds of oil used as substrate.     

Crystalline complex between poly(γ-methyl l-glutamate) and dimethyl phthalate

The crystalline complex between poly(γ-methyl l-glutamate) (PMLG) and dimethyl phthalate (DMP) has been formed in films cast from a solution in dichloroethane. It has the stoichiometry of 1 mol of DMP to three or four residues of PMLG and shows two definite characteristics in X-ray diffraction patterns; one is the large hexagonal unit cell with the edge of around 28 Å and another the ‘extra’ 5.07 Å meridional reflection which can not be interpreted by a PMLG α-helical conformation. The structural examination for the films with various DMP contents is carried out by X-ray, viscoelastic, and d.s.c. measurements and the following structure is proposed for the crystalline complex. Four PMLG are associated to form a group which is hexagonally packed and DMP molecules, located in the gaps between groups, form a specific favourable helical structure along PMLG chains in which the van der Waals stacking of benzene rings of DMP is significant.     

Cationic copolymerization behavior of a bicyclic orthoester having hydroxy group with glycidyl phenyl ether and volume change on their copolymerization

This article describes cationic ring‐opening copolymerization of a bicyclic orthoester having hydroxy group (BOE‐OH) and glycidyl phenyl ether (GPE), and the volume shrinkage behavior during the copolymerization. THF soluble polyethers [poly(BOE‐OH‐co‐GPE)] were obtained by the copolymerizations at 80–180°C, while crosslinked poly(BOE‐OH‐co‐GPE) was obtained by the copolymerizations at 220–250°C. This crosslinking reaction may originate from the dehydration of methylol groups in the side chain of poly(BOE‐OH‐co‐GPE). The volume shrinkage during the cationic copolymerization reduced as the increase of the BOE‐OH feed ratio. By contrast, the volume shrinkage on the crosslinking polymerization was almost independent on the BOE‐OH feed ratio. Poly(BOE‐OH‐co‐GPE)s with higher BOE‐OH composition showed lower thermal weight loss temperature owing to the release of H₂O by dehydration of methylol groups. The BOE‐OH component in the THF soluble poly(BOE‐OH‐co‐GPE)s lowered the glass transition temperature (T_g), while that in the crosslinked poly(BOE‐OH‐co‐GPE) increased the T_g probably because of the higher crosslinking density. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1356–1361, 2006     

Synthesis of poly(tetrahydrofuran-b-ε-caprolactone) macromonomer via the Sml2-induced transformation

Summary A novel well-defined macromonomer consisting of different types of monomers in polymerization mechanisms was synthesized for the first time through the SmI₂-induced transformation. The macromonomer, -methacryloylpoly-(tetrahydrofuran-b--caprolactone), was prepared by the reaction of methacryloyl chloride with living poly(tetrahydrofuran-b--caprolactone) [poly(THF-b-CL)] which was obtained by the two-electron reduction of the cationic growing center of poly(THF) by samarium iodide (SmI₂) followed by the polymerization of CL. ¹H NMR analysis indicated the quantitative introduction of the methacryloyl group onto the polymer end. The molecular weight distribution of the macromonomer was relatively narrow, and the unit ratio of THF to CL could be controlled by both polymerization time of THF and the amount of CL, resulting from the living nature of both CL- and THF-polymerizations. Radical copolymerization of the produced macromonomers with methyl methacrylate in the presence of AIBN resulted in a polymethacrylate backbone grafted with poly(THF-b-CL) block copolymers.     

Rearrangement of the main chain of the organocobalt polymers

The polymers 3 having pyridine moieties in the main chain were synthesized by the reaction of the organocobalt polymers 1 having cobaltacyclopentadiene moieties in the main chain with various nitriles 2. When brown colored 1 and excess 2 were heated in tetrahydrofuran at 80 °C for 24 h and then at 150 °C for 12 h in a sealed tube, the polymers 3 were obtained by the precipitation with methanol in good yields. From the spectroscopic measurements, the resulting polymers 3 were found to contain 35 – 90% of the pyridine moieties depending on the structures of 1. Received: 7 July 1997/Revised: 14 August 1997/Accepted: 25 August 1997     

Oxidation of synthetic triacylglycerols containing eicosapentaenoic and docosahexaenoic acids: Effect of oxidation system and triacylglycerol structure

Thirteen synthetic triacylglycerols (TAG) containing eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) were oxidized in the presence of 2,2′-azobis(2,4-dimethyl-valeronitrile) (AMVN) and 2,2′-azobis(2-amidinopropane)dihydrochloride (AAPH) as aqueous and nonaqueous radical initiators to investigate the influence of TAG structure and oxidation system on the oxidative stability of TAG that contain highly unsaturated fatty acids (HUFA). A 2:1 (mol/mol) mixture of trieicosapentaenoylglycerol and tripalmitoylglycerol was most susceptible to the AMVN-initiated oxidation among three types of TAG that contained EPA and palmitic acid (2:1, mol/mol). Compared with 1,2 (or 2,3)-dieicosapentaenoyl-3(or 1)-palmitoylglycerol (EEP) and 1,3-dieicosapentaenoyl-2-palmitoylglycerol (EPE), the oxidative rate of EEP was somewhat higher. A similar result was obtained for DHA-containing TAG. The oxidative rate of TAG that contained EPA and palmitic acid (1:2, mol/mol) showed a positive correlation with the amount of EPA in a single TAG molecule. Moreover, in the nonaqueous system, the oxidative rate of EPA-containing TAG was affected by unsaturation and carbon chainlength of constituent fatty acids. In the AAPH-initiated oxidation in the aqueous system, the oxidative rate of TAG with EPA and palmitic acid was higher with the increased quantity of EPA in a single TAG molecule. Also, constituent fatty acids modified the oxidative rate of EPA-containing TAG in an aqueous system. The glycerol position of EPA and DHA also affected the oxidative rate of the TAG. EPA and DHA located at the 1,2 (or 2,3)-position of glycerol were more oxidizable than those at the 1,3-position during AAPH-initiated oxidation. Thus, 1,2(or2,3)-dipalmitoyl-3(or 1)-eicosapentaenoylglycerol was oxidized faster than 1,3-dipalmitoyl-2-eicosapentaenoylglycerol. These observations suggest that the oxidative stability of TAG that contain HUFA could be modulated by the oxidation system and TAG structure.     

Effect of Agglomeration on Mechanical Properties of Porous Zirconia Fabricated by Partial Sintering

Porous ZrO₂ ceramics were fabricated by compacting a fine ZrO₂ powder, followed by pressureless sintering. Two unidirectional pressures of 30 and 75 MPa were used to prepare the green compacts. The strength and the fracture toughness of porous ZrO₂ specimens sintered from the compacts prepared by 75 MPa were substantially higher than those by 30 MPa, especially for the specimens with low porosity. However, the corresponding Young's moduli were identical. This caused the strain to failure of these porous bodies to increase significantly with increasing compaction pressure. Microstructural analyses showed that a number of voids and small flaws existed in the green compacts prepared by the lower pressure, due to the agglomeration of fine ZrO₂ grains. It was revealed that the ZrO₂ agglomeration resulted in a localized nonuniform shrinkage and degraded the mechanical properties of porous ZrO₂ ceramics.     

Retardation of volatile aldehyde formation in the exhaust of frying oil by heating under low oxygen atmospheres

Volatile aldehydes were generated in the exhaust of high-oleic safflower oil during heating at 180°C by spraying water into atmospheres with four levels of oxygen concentrations (2, 4, 10, and 20%). These aldehydes were quantitatively analyzed by HPLC after the conversion to 2,4-dinitrophenyl hydrazones. Ten alkanals (C₂ through C₁₀), eight 2-alkenals (C₃ through C₁₀) and three 2,4-alkadienals (C₇, C₉, and C₁₀) were found. These aldehyde levels were found to be positively correlated with both the heating time and the atmospheric oxygen concentration. The total amounts of aldehydes were the lowest in the oil heated in an atmosphere with 2% O₂, and corresponded to 1/10 of those in the atmosphere with 20% O₂. Acrolein was not found in oils heated in the atmosphere with 2% oxygen. These results suggest that frying in atmospheres with low oxygen levels can effectively decrease the generation of volatile aldehydes in the exhaust.     

High oleic acid oil suppresses lung tumorigenesis in mice through the modulation of extracellular signal-regulated kinase cascade

This study was undertaken to estimate the effect of dietary high oleic acid oil (OA) on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in mice. Diet containing 10% oil was fed to mice through experimental periods. On day 30 after NNK injection (100 mg/kg body weight, i.p.), the treatment increased the level of prostaglandin E₂ (PGE₂) as well as proliferating cell nuclear antigen, a marker of cell proliferation in a high linoleic acid oil (LA)-fed group but not in an OA-fed group. The NNK treatment also induced the activation of an extracellular signal-regulated kinase (Erk) cascade (Erk, Mek and Raf-1) in an LA-fed group. On the other hand, OA feeding abolished the NNK-induced activation of the Erk cascade. In conjugation with these events, OA feeding reduced lung tumor incidence and tumor multiplicity (percentage of mice with tumors) in mice compared with LA feeding at the 20th experimental week. These results suggest that OA suppresses lung tumorigenesis and that this suppression is correlated with the inhibition of PGE₂ production and inactivation of the Erk cascade.     

Polymeric phosphonium salts as a novel class of cationic biocides. VII. Synthesis and antibacterial activity of polymeric phosphonium salts and their model compounds containing long alkyl chains

Various polymeric phosphonium salts containing long alkyl chains (C₁₀? C₁₈) and their corresponding model compounds were prepared, which possess the same hydrophobic structure as that of the common disinfectants (quaternary ammonium salts), and their antibacterial activities were evaluated by means of the viable cell counting method against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). The polymer with the decyl group exhibited a higher activity than that of the corresponding model compound, particularly against the Gram-positive strain. Furthermore, antibacterial activity of the polymers was found to decrease as the chain length increased. In contrast with the polymers, the antibacterial activity of the corresponding model compounds increased as hydrophobicity of the substituents increased. The antibacterial activity was strongly dependent on the structure, particularly on the length of the alkyl chain. © 1994 John Wiley & Sons, Inc.