Lars Müller

In vitro antioxidant activity of tocopherols and tocotrienols and comparison of vitamin E concentration and lipophilic antioxidant capacity in human plasma.

A comparative study investigated four tocopherols, four tocotrienols, and alpha-tocopheryl acetate on their antioxidative activities in five different popular assays, which were adapted to non-polar antioxidants. alpha-Tocopherol, used as calibration standard, showed the highest ferric reducing antioxidant power. Greater ring methyl substitution not only led to an increase of scavenging activity against the stable 2,2-diphenyl-1-picrylhydrazyl radical, but also to a decrease in oxygen radical absorbance capacity. Regarding alpha-tocopherol equivalent antioxidant capacity no significant differences in the antioxidant activity of all vitamin E isoforms were found. In contrast, a significantly lower peroxyl radical-scavenging activity of alpha-tocochromanols was determined in a chemiluminescence assay. Except oxygen radical absorbance capacity, no significant differences of the antioxidant activity related to the side chain could be detected. The data show that the reducing ability and radical chain-breaking activity of the several vitamin E forms depends on the circumstances under which the assays are performed. In our opinion, the used lipophilic methods can be useful for estimating the antioxidant activity of strong non-polar antioxidants, e.g. carotenoids, too. Furthermore, we could show a significant correlation between the total tocopherol content in human plasma and the lipophilic antioxidant capacity measured by alpha-tocopherol equivalent antioxidant capacity and 2,2-diphenyl-1-picrylhydrazyl.

Lack of effects of tomato products on endothelial function in human subjects: results of a randomised, placebo-controlled cross-over study.

Epidemiological studies suggest that consumption of tomato products reduces the risk of CVD via antioxidant, hypocholesterolaemic and anti-inflammatory mechanisms. Although experimental data also describe beneficial effects on endothelial function, clinical data in human subjects are lacking. To test the hypothesis that tomato ingestion ameliorates endothelial function, we randomised healthy non-smoking postmenopausal women to consume a buttered roll with and without tomato purée (70 g) in a cross-over design. Endothelial-dependent flow-mediated dilation (FMD) and endothelial-independent nitro-mediated dilation of the brachial artery were assessed with high-resolution ultrasound (13 MHz linear array transducer). Acute (24 h) and long-term (7 d) effects were examined after daily consumption of the described meal. Nineteen volunteers completed the protocol and provided technically suitable ultrasound measurement data. Plasma lycopene levels increased from 0·30 (sem 0·04) (baseline) to 0·42 (sem 0·04) and to 0·74 (sem 0·06) μm after 24 h and 7 d, respectively, with tomato purée consumption. These data indicated an effective absorption of the tomato product. However, both acute and long-term tomato purée consumption had no effects on endothelium-dependent or -independent dilation of the brachial artery. In addition, we found no correlation between lycopene plasma levels and FMD. In conclusion, consumption of tomato products associated with a significant increase in plasma lycopene levels had no effects on endothelial function in healthy postmenopausal women.

Antioxidant capacity of tomato seed oil in solution and its redox properties in cultured macrophages

The health benefits of tomato seed oil (TSO) have been suggested to be related to its antioxidant activity, although at the moment not much information is available on the antioxidant effects of TSO in biological systems. In this paper, we evaluated the antioxidant capacity of TSO using different spectrophotometrical antioxidant assays (LPSC, FRAP, αTEAC, DPPH). Moreover, we determined the ability of TSO in inhibiting oxidative stress in human cultured macrophages. The peroxyl radical scavenging LPSC assay was the most sensitive assay to detect the antioxidant capacity of the TSO, followed by the DPPH, FRAP, and αTEAC assay. TSO was able to counteract spontaneous and H₂O₂-induced oxidative stress in human macrophages, limiting intracellular ROS production and controlling oxidative stress signaling. In particular, TSO was able to decrease the phosphorylation of the MAPK ERK1/2, JNK, and p-38, activation of the redox-sensitive NF-kB, and expression of the heat shock proteins 70 and 90. When the antioxidant capacity of TSO was compared with that of purified lycopene, inhibition of ROS production by TSO was remarkably higher. This was due to the high content of other antioxidants in TSO, including (5Z)-, (9Z)-, (13Z)-, and (15Z)-lycopene isomers, β-carotene, lutein, γ-tocopherol, and α-tocopherol.

Two approaches of studying singularity of projective conics

The singularity of a projective conic can be determined via the associated matrix to the implicit equation of the projective conic. In this expository article, we will first derive a known result for determining the singularity of a projective conic via the associated matrix. Then we will introduce the concepts of μ-basis of the parametric projective conics, and close with the same criteria via μ-basis method.