Formation of Toxic α,β-Unsaturated 4-Hydroxy-Aldehydes in Thermally Oxidized Fatty Acid Methyl Esters

To investigate the heat induced formation of α,β-unsaturated 4-hydroxy-aldehydes (4-hydroxy-2-trans-hexenal (HHE), 4-hydroxy-2-trans-octenal (HOE), 4-hydroxy-2-trans-nonenal (HNE) and 4-hydroxy-2-trans-decenal (HDE)) fatty acid methyl esters (FAMEs) of stearic, oleic, linoleic and linolenic acids were heated separately at 185°C for 0 to 6 hrs. The formation of 2,4-decadienal, a suspected intermediate in HNE formation, was also measured in these FAMEs. As expected methyl stearate (MS) and methyl oleate (MO) did not produce any of the α,β-unsaturated 4-hydroxy-aldehydes as a consequence of thermally induced lipid peroxidation. The formation of HHE was detected in both methyl linoleate (ML) and methyl linolenate (MLN), with concentration higher in MLN than in ML. The maximum HHE concentration was 3.99 μg HHE/g ML after 2 h and 50.78 μg HHE/g MLN after 4 h of heat treatment. HOE was detected in both ML and MLN, and the maximum concentration was 102.50 μg HOE/g ML after 6 h and 90.56 μg HOE/g MLN after 2 h of heating. HNE was found only in ML and its highest concentration was 84.82 μg HNE/g ML after 3 h of heating. HDE was not detected in any of the four heat treated FAMEs. 2,4-Decadienal was not found to be an intermediate in the formation of HNE in thermally induced oxidation of FAMEs.     

Potential impact of former Zn ore extraction activities on dissolved uranium distribution in the Riou-Mort watershed (France)

The industrial basin of Decazeville (Riou-Mort watershed, South-West France) is well known for its heavy metal pollution and its subsequent environmental effects on the Lot-Garonne River system. The source of this pollution is the Riou-Mort River, which drains smelting waste areas. A first survey after remediation works has revealed elevated dissolved uranium (U(D)) concentrations in the outlet of the Riou-Mort River. The objective of this research is to identify the origin of U(D) in the Riou-Mort watershed and to evaluate the impact of industrial activities on this element. Uranium was measured at 10 water sampling sites, located upstream and downstream the industrial basin, and in three smelting waste deposits. Uranium concentrations in the smelting waste deposits reach up to 14.4 mg kg(-1) and (234U/238U) activity ratios (AR) are near unity. Dissolved U concentrations in the Riou-Mort River and its main tributaries ranges over two orders of magnitude from 0.02 to 6.1 microg L(-1). The highest levels were measured in a site with no anthropogenic pollution, upstream from the industrial area. This observation suggests that U(D) is mainly linked to weathering; the elevated U concentrations originate from the naturally occurring radioactive materials (NORM) located in the Permian bedrock and no significant U pollution exists, at present, in the Riou-Mort watershed. This work demonstrates that spatial monitoring coupled with a long time-series are an essential prerequisite in assessment of spatiotemporal variations of U(D), prior to a diagnostic of pollution in a small watershed.     

α-tocopherol oxidation mediated by superoxide anion (O 2 − ). II. Identification of the stable α-tocopherol oxidation products

The present paper describes the identification of two stable end products of α-tocopherol oxidation that were previously detected among the products of the reaction of α-tocopherol with superoxide anion (O ₂ ⁻ ) under aprotic conditions. One compound, previously designated compound A, was identified astrans-7-hydroxy-trans-8,8a-epoxy-α-tocopherone, and the other, designated compound B, was identified ascis-7-hydroxy-cis-8,8a-epoxy-α-tocopherone. It was also observed that under protic conditions (10% water in acetonitrile) the reaction of α-tocopherol with O ₂ ⁻ did not produce compounds A and B, but rather α-tocopheryl quinone, α-tocopherol dimer, α-tocopherol dihydroxy dimer, and the previously designated compound C. Compound C was identified in the present study as α-tocopheryl-quinone-2,3-epoxide.     

A glutamic Acid-producing lactic Acid bacteria isolated from malaysian fermented foods

l-glutamaic acid is the principal excitatory neurotransmitter in the brain and an important intermediate in metabolism. In the present study, lactic acid bacteria (218) were isolated from six different fermented foods as potent sources of glutamic acid producers. The presumptive bacteria were tested for their ability to synthesize glutamic acid. Out of the 35 strains showing this capability, strain MNZ was determined as the highest glutamic-acid producer. Identification tests including 16S rRNA gene sequencing and sugar assimilation ability identified the strain MNZ as Lactobacillus plantarum. The characteristics of this microorganism related to its glutamic acid-producing ability, growth rate, glucose consumption and pH profile were studied. Results revealed that glutamic acid was formed inside the cell and excreted into the extracellular medium. Glutamic acid production was found to be growth-associated and glucose significantly enhanced glutamic acid production (1.032 mmol/L) compared to other carbon sources. A concentration of 0.7% ammonium nitrate as a nitrogen source effectively enhanced glutamic acid production. To the best of our knowledge this is the first report of glutamic acid production by lactic acid bacteria. The results of this study can be further applied for developing functional foods enriched in glutamic acid and subsequently γ-amino butyric acid (GABA) as a bioactive compound.     

Temperature Dependence of HNE Formation in Vegetable Oils and Butter Oil

The temperature dependence of the formation of toxic 4-hydroxy-2-trans-nonenal (HNE) was investigated in high and low linoleic acid (LA) containing oils such as corn, soybean and butter oils. These oils contain about 60, 54 and 3–4% of LA for corn, soybean and butter oils, respectively. The oils were heated for 0, 0.5, 1, 2, and 3 h at 190 °C and for 0, 5, 15 and 30 min at 218 °C. HNE concentrations in the oils were analyzed by high performance liquid chromatography (HPLC). The maximum HNE concentrations in heated (190 °C) corn, soybean and butter oils were 5.46, 3.73 and 1.85 μg HNE/g oil, respectively. The concentration of HNE at 218 °C increased continuously for all the three oils, although they were heated for much shorter periods compared to the lower temperature of heating (190 °C). HNE concentration at 30 min reached the maximum of 15.48, 10.72 and 6.71 μg HNE/g oil for corn, soybean and butter oils, respectively. HNE concentration at higher temperature (218 °C) was 4.9, 3.7, and 8.7 times higher than at the lower temperature (190 °C) and 30 min of heating for corn, soybean and butter oils, respectively. It was found that HNE formation was temperature dependant in the tested oils.