Antioxidant Mobilization Research Articles

Antioxidant Activity of Foods: Development of Singlet Oxygen Absorption Capacity (SOAC) Assay Method.

Recently a new assay method that can quantify the singlet oxygen absorption capacity (SOAC) of antioxidants (AOs) and food extracts was proposed. Singlet oxygen (1O2) quenching rates (kQ) and the relative SOAC values were measured for many carotenoids and phenolic AOs in ethanol/chloroform/D2O (50 : 50 : 1, v/v/v) solution at 35ºC using UV-vis spectrophotometry. It has been clarified that the SOAC method is useful to evaluate the 1O2-quenching activity of lipophilic and hydrophilic AOs having 5 orders of magnitude different rate constants (kQ). Measurements of the kQ and SOAC values were also performed for 39 kinds of food extracts. The results indicate that the SOAC method is useful to evaluate the 1O2-quenching activity of food extracts having two orders of magnitude different kQ values. Further, the kQ values for the reaction of 1O2 with 8 carotenoids and 8 vitamin E homologues were measured in an aqueous Triton X-100 (5.0 wt %) micellar solution (pH 7.4). Results obtained demonstrate that the kQ values of AOs in homogeneous and heterogeneous solutions vary notably depending on (i) polarity (dielectric constant (ε)) of the reaction field between AOs and 1O2, (ii) local concentration of AOs, and (iii) mobility of AOs in solution. Measurements of kQ and SOAC values in a micellar solution may be useful for evaluating the 1O2-quenching activity of AOs in biological systems. Furthermore, measurements of the SOAC values were performed for 32 kinds of food extracts using a microplate reader. The SOAC assay method was validated by inter-laboratory validation study due to 14 laboratories.

Measurements of Singlet Oxygen-Quenching Activity of Vitamin E Homologs and Palm Oil and Soybean Extracts in a Micellar Solution.

Recently, a new assay method that can quantify the singlet oxygen-absorption capacity (SOAC) of antioxidants (AO) and food extracts in homogeneous organic solvents has been proposed. In the present study, second-order rate constants (kQ ) for the reaction of singlet oxygen (1 O2 ) with vitamin E homologs (α-, β-, γ-, and δ-tocopherols [Toc] and α-, β-, γ-, and δ-tocotrienols [Toc-3]) were measured in an aqueous Triton X-100 (5.0 wt%) micellar solution (pH 7.4). Toc-3 showed kQ values larger than those of Toc in a micellar solution, although Toc and Toc-3 showed the same kQ values in a homogeneous solution. Similar measurements were performed for 5 palm oil extracts 1-5 and one soybean extract 6, which contained different concentrations of Toc, Toc-3, and carotenoids. It has been clarified that the 1 O2 -quenching rates (kQ ) (that is, the relative SOAC value) obtained for extracts 3-6 may be explained as the sum of the product <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mfenced><mml:mrow><mml:mi>Σ</mml:mi><mml:msubsup><mml:mi>k</mml:mi><mml:mi>Q</mml:mi><mml:mrow><mml:mi>AO</mml:mi><mml:mo>-</mml:mo><mml:mi>i</mml:mi></mml:mrow></mml:msubsup><mml:mfenced><mml:mrow><mml:mi>AO</mml:mi><mml:mo>-</mml:mo><mml:mi>i</mml:mi></mml:mrow></mml:mfenced><mml:mo>/</mml:mo><mml:mn>100</mml:mn></mml:mrow></mml:mfenced></mml:math> of the rate constant ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>k</mml:mi><mml:mi>Q</mml:mi><mml:mrow><mml:mi>AO</mml:mi><mml:mo>-</mml:mo><mml:mi>i</mml:mi></mml:mrow></mml:msubsup></mml:math> ) and the concentration ([AO-i]/100) of AO-i contained. The UV-vis absorption spectra of Toc and Toc-3 were measured in a micellar solution and chloroform. The results obtained demonstrated that the kQ values of AO in homogeneous and heterogeneous solutions vary notably depending on (1) polarity (dielectric constant [ε]) of the reaction field between 1 O2 and AO, (2) the local concentration of AO, and (3) the mobility of AO in solution. The results suggest that the SOAC method is applicable to the measurement of 1 O2 -quenching activity of general food extracts in a heterogeneous micellar solution.

Plasma antioxidants and lipid oxidation after submaximal resistance exercise in men.

An increased generation of reactive oxygen species occurs during exercise. We investigated whether changes in plasma antioxidants and lipid oxidation products after submaximal resistance exercise are detectable, and whether training status has any effect on changes. Seven resistance trained (RT, 31.3 +/- 10.2 yrs) and ten non-resistance trained male subjects (NRT, 28.2 +/- 3.9 yrs) performed a submaximal resistance exercise circuit (10 different exercises, 75% of 1-repetition maximum, 18.6 +/- 1.1 minutes). Blood samples were taken before and immediately after exercise. Plasma antioxidants (AO), lipid oxidation products malondialdehyde (MDA) and conjugated dienes (CD) were measured using HPLC and/or photometric detection. Groups were compared using the Mann-Whitney U test, the exercise effect was tested using the Wilcoxon signed ranks test. P < 0.05 was regarded as significant. alpha-Tocopherol, gamma-tocopherol, beta-carotene, lycopene, ascorbic acid,MDA and CD concentrations did not differ between groups at rest. There was a similar increase of fat soluble plasma AO in both groups after exercise, but not ascorbic acid. MDA increased also in both groups after exercise, but CD increased only in NRT. There is no difference in plasma AO and lipid oxidation products in RT and NRT at rest. After short time resistance exercise there is a mobilization of fat soluble AO. Despite mobilization of AO, oxidative stress occurs during submaximal resistance exercise, which is indicated by increased MDA and CD concentrations. As exercise induced an increase of CD only in NRT, it seems that regular resistance training partly prevents lipid peroxidation during exercise.