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Soy sauce is a traditional fermented seasoning in Asian countries, that has high antioxidant activity in vitro and some antioxidant activity in vivo. We attempted to identify the major antioxidants present, using the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay as a guide. 3-Hydroxy-2-methyl-4H-pyran-4-one (maltol) was one of several active compounds found in an ethyl acetate extract of dark soy sauce (DSS) and was present at millimolar concentrations in DSS. However, most of the antioxidant activity was present in colored fractions, two of which (CP1 and CP2) were obtained by gel filtration chromatography. Their structural characteristics based on nuclear magnetic resonance (NMR) and electrospray-ionization time-of-flight mass spectrometry (ESI-TOF-MS) analysis suggest that carbohydrate-containing pigments such as melanoidins are the major contributors to the high antioxidant capacity of DSS.

No abstract is provided for this article.

The antioxidant action of a series of benzylisoquinoline alkaloids has been investigated. Laudanosoline, protopapaverine, anonaine, apomorphine, glaucine, boldine, bulbocapnine, tetrahydroberberine and stepholidine produced a dose-dependent inhibition of microsomal lipid peroxidation induced by Fe2+/ascorbate, CCl4/NADPH or by Fe3+ADP/NADPH. Apomorphine exerted the highest inhibitory effects in the three systems of induction used, with a potency higher than propyl gallate. Laudanosoline was particularly effective in the first system, while bulbocapnine and anonaine were more potent when CCl4/NADPH or Fe3+ -ADP/NADPH were used as inducers. Laudanosoline, protopapaverine, apomorphine, tetrahydroberberine and stepholidine were also potent inhibitors of nitroblue tetrazolium (NBT) reduction. The presence of a free hydroxyl group or preferably of a catechol group is a feature relevant for inhibition of lipid peroxidation and NBT reduction, nevertheless the antioxidant activity of benzylisoquinoline alkaloids cannot be only ascribed to the formation of phenoxy radicals and other free radical species may be formed during aporphine and tetrahydroprotoberberine oxidation. The influence of this series of compounds on the time course of lipid peroxidation suggests that some of them, like apomorphine and boldine act as chain-breaking antioxidants.

In addition to excretion of metabolic waste products, organic ionic transporters facilitate uptake of specific compounds of physiological importance. In animals, the organic cation transporter, OCTN1 was found to enable the specific uptake of the unique amino acid, ergothioneine (EGT). EGT can accumulate in the body at up to millimolar concentrations and is believed to function as a physiological antioxidant. However the main function of EGT and the reasons for its active accumulation in the body remain obscure. Through bioinformatic approaches, we identified an analogous EGT transporter in the nematode, Caenorhabditis elegans. The present study investigated and characterized deletion mutants of this gene, OCT-1, in the nematodes. Gene deletion mutations of the OCT-1 transporter were shown to decrease overall lifespan of the worms and increase oxidative damage. However the absence of impaired EGT uptake and the inability of excess EGT to rescue the debilitating phenotype indicate that EGT transport does not explain the deleterious effects of the gene deletion.

In the present study, we investigated the effect of the dopaminergic neurotoxin 6‐hydroxydopamine (6‐OHDA) on hydroxyl free radical and peroxynitrite formation in vivo using d ‐phenylalanine as a novel mechanistic probe. In vivo microdialysis was carried out in the striatum of freely moving male Wistar rats. The microdialysis probes were perfused with artificial cerebrospinal fluid containing 5 m m d ‐phenylalanine (flow rate 2 µL/min). After obtaining a stable baseline 6‐OHDA was delivered into the striatum via reverse microdialysis for 60 min. HPLC measurements of the effluent were performed using photodiode array detection for determination of phenylalanine derived o ‐tyrosine and m ‐tyrosine (as hydroxylation markers) as well as of nitrotyrosine and nitrophenylalanine (as nitration markers). The basal levels of the hydroxylation derived products of phenylalanine were approximately 100‐fold higher than those of the nitration derived products. 6‐OHDA (0.1, 1, 10 m m ) significantly increased o ‐ and m ‐tyrosine up to nine‐ and 13‐fold, respectively, whereas levels of 3‐nitrotyrosine and 4‐nitrophenylalanine were significantly increased up to 422‐ and 358‐fold, respectively. The results demonstrate that phenylalanine is a sensitive in vivo marker for 6‐OHDA‐induced hydroxylation and nitration reactions which are clearly concentration dependent. We conclude that peroxynitrite formation is involved in 6‐OHDA‐induced neurochemical effects.

Peroxisome proliferators have been found to induce hepatocarcinogenesis in rodents, and may cause mitochondrial damage. Consistent with this, clofibrate increased hepatic mitochondrial oxidative DNA and protein damage in mice. The present investigation aimed to study the mechanism by which this might occur by examining the effect of clofibrate on freshly isolated mouse liver mitochondria and a cultured hepatocyte cell line, AML-12. Mitochondrial membrane potential (ΔΨm) was determined by using the fluorescent dye 5,5′,6,6′-tetrachloro-1,1′, 3,3′-tetraethyl-benzimidazolylcarbocyanine iodide (JC-1) and tetramethylrhodamine methyl ester (TMRM). Application of clofibrate at concentrations greater than 0.3 mM rapidly collapsed the ΔΨm both in liver cells and in isolated mitochondria. The loss of ΔΨm occurred prior to cell death and appeared to involve the mitochondrial permeability transition (MPT), as revealed by calcein fluorescence studies and the protective effect of cyclosporin A (CsA) on the decrease in ΔΨm. Levels of reactive oxygen species (ROS) were measured with the fluorescent probes 5-(and-6)-carboxy-2′,7′-dichlorofluorescein diacetate (DCFDA) and dihydrorhodamine 123 (DHR123). Treatment of the hepatocytes with clofibrate caused a significant increase in intracellular and mitochondrial ROS. Antioxidants such as vitamin C, deferoxamine, and catalase were able to protect the cells against the clofibrate-induced loss of viability, as was CsA, but to a lesser extent. These results suggest that one action of clofibrate might be to impair mitochondrial function, so stimulating formation of ROS, which eventually contribute to cell death.