Guy Yardeni

Role of Radicals in the Lipid Peroxidation Products of Commercial Infant Milk Formula

Four commercial brands of infant milk formula were investigated, and the amount of shelf lipid peroxidation was determined by measuring malondialdehyde (MDA) or, more exactly, thiobarbituric acid reactive substance (TBARS) levels, which are the end products of lipid peroxidation. TBARS level, indicated by MDA concentration, was higher in the vegetarian brands. The vegetarian brands are, as expected, more prone to oxidation than dairy brands, as they contain more unsaturated fats. The introduction of formate anion diminishes the peroxide amounts initially present in the milk samples as well as those induced by radiation-induced oxidation.

Effect of Hydrogen Pretreatment of Platinum Nanoparticles on their Catalytic Properties: Reactions with Alkyl Radicals – A Mechanistic Study

Methyl radicals react with platinum nanoparticles (NPs) suspended in aqueous solutions to form (Pt0‐NPs)‐(CH3)n as a stable major product. Hydrogen gas treatment of the Pt0‐NPs affects the composition of the products and the surface reactions. The results clearly point out that pretreatment of Pt0‐NPs and (Pt0‐NPs)‐(CH3)n with H2 considerably affects their reactions with methyl radicals. The implications of the results on catalytic processes are discussed.

H/D kinetic isotope effect as a tool to elucidate the reaction mechanism of methyl radicals with glycine in aqueous solutions.

The H/D kinetic isotope effect (KIE) for the reaction of methyl radicals with glycine in aqueous solutions at pH 10.6 equals 16 ± 3. This result proves that the methyl radical abstracts a hydrogen atom from the methylene group of glycine and not an electron from the unpaired couple on the nitrogen atom. The rate constant of the reaction of methyl radicals with glycine at pH 7.0 is orders of magnitude smaller than that at pH 10.6.

Copper(II) catalyses the reduction of perchlorate by both formaldehyde and by dihydrogen in aqueous solutions

Abstract During an effort to synthesize the trans-III-copper(II) complex with 1,4,8,11-tetramethyl-pyro-phosphonate-1,4,8,11-tetra-aza-cyclo-tetradecane, using only perchlorate salts, it was noted that the perchlorate is reduced to chloride. Analysis of the reactions leading to this surprising result points out that Cu(H2O)42+ catalyzes the reduction of perchlorate by H2 and by CH2O. These reactions are slow at room temperature and ambient pressures. A plausible mechanism, supported by DFT calculations, is proposed pointing out that the role of CuH+ under mild conditions cannot be ignored.

Crystal structure of (acetato-κO)(ethanol-κO)[(9S,17S,21S,29S)-9,17,21,29-tetra­hydroxy-18,30-dioxa­octa­cyclo­[18.10.0.02,7.08,19.09,17.011,16.021,29.023,28]triaconta-1,3,5,7,11(16),12,14,19,23(28),24,26-undeca­ene-10,22-dione-κ3O18,O21,O22]caesium ethanol monosolvate

The title compound, C28H16O8·Cs+CH3O−·2CH3CH2OH, was formed in the supramolecular reaction between a vasarene analogue and caesium fluoride, where the F− ion has been replaced by acetate.

Role of lycopene in preventing lipid peroxidation products, in commercial infant milk formula

Abstract Objectives: The aim of the study was to investigate whether lycopene from natural sources (tomato extract) is able to protect newborns milk formula, against oxidative damage caused by exposure to hydroxyl radicals, and is there a difference between milk substitutes from various sources. Methods: Four commercial brands of infant milk formula: two of the formulas were dairy milk (A-d and B-d) and two were based on soy bean vegan milk (A-s and B-s), were exposed to ionizing radiation radical (·OH). Lipid peroxidation was determined by measuring malondialdehyde (MDA) using thiobarbituric acid reactive substance test (TBARS). Results: When suspensions containing the four brands of formula were subjected to oxidizing media produced by ionizing radiation (hydroxyl radicals), lipid peroxidation increased linearly as a function of the irradiation dose (R = 0.99). It was found that lycopene in a concentration of 0.6 mM, reduced the radiation damage only in the soy-based formula; decrease of ∼40% of the damage achieved in B-s, and ∼20% reduction in the damage caused to A-s, significantly p < 0.01. Conclusions: Lycopene in dairy milk did not protect against hydroxyl radicals; however, lycopene found to protect against hydroxyl radicals in soy milk. This result suggests different mechanisms of radical production that arises from high iron levels present in the soy milk and involving the high-valent iron peroxo species.