Neuroprotective effects of white tea against oxidative stress-induced toxicity in striatal cells.

Tea is one of the most widely consumed beverages in the world and represents an important source of antioxidants mainly catechins that confer beneficial effects in reducing the risk of cardiovascular diseases, age-related disorders or cancer. In the central nervous system, oxidative stress caused by increased production of reactive oxygen and nitrogen species represents an important mechanism for neuronal dysfunction and cell loss in different neurodegenerative disorders. The neuroprotective effects of green-tea-derived polyphenols have extensively been demonstrated in different models of neurotoxicity. However, few data have been reported on the antioxidant activity of white tea extracts in the nervous system. In the present study, we demonstrate that white tea extracts protect striatal cell lines against oxidative stress-mediated cell death. The effects of white tea on protection of striatal cell cultures are likely associated with the antioxidant properties of white tea components since neuronal cell loss induced by nonoxidative insults such as D1 dopamine receptor activation cannot be prevented by pre-treatment with white tea. Altogether our results suggest that regular consumption of white tea may contribute to reduce oxidative stress associated with brain injury and be clinically useful for treating age-related and neurodegenerative disorders.

Effect of pH on the antimicrobial activity and oxidative stability of oil-in-water emulsions containing caffeic acid.

Antioxidant properties in food are dependent on various parameters. These include the pH value and interactions with food components, including proteins or metal ions. Food components affect antioxidant stability and also influence the properties of microorganisms and their viability. This paper describes an investigation of the effect of pH on the antioxidant and antibacterial properties of caffeic acid in different media. The pH values studied, using an oil-in-water emulsion as model system, were 3, 5 (with and without phosphate buffer), and 9. Effects of mixtures of caffeic acid, bovine serum albumin (BSA), and Fe (III) on oxidative deterioration in the emulsion samples were studied. The results show that the antioxidant activity of caffeic acid was increased by the presence of BSA. This effect was pH dependent and was affected by the presence of iron ions. Antibacterial properties were also pH dependent. The minimum concentration of caffeic acid required to inhibit some microorganisms in the pH range of 5 to 7 was determined. A concentration of 0.4% (w/w) caffeic acid was enough to inhibit the growth of some of the studied microorganisms in the pH range of 5 to 7. However, near-neutral pH concentrations higher than 0.4% were needed to inhibit some microorganisms, including Listeria monocytogenes, E. coli, and Staphylococcus aureus, in the medium.