title: Effects of Environmental pH on Antioxidant Interactions between Rosmarinic Acid and α-Tocopherol in Oil-in-Water (O/W) Emulsions.
abstract: Antioxidant regeneration could be influenced by various factors such as antioxidant locations and pH conditions. The effects of environmental pH on the antioxidant interaction between rosmarinic acid and α-tocopherol in oil-in-water (O/W) emulsions were investigated. Results showed that the combined antioxidants at pH 7 exhibited the strongest synergistic antioxidant activity in comparison with the combinations at other pH conditions as indicated by the interaction index. A drop in pH from 7 to 3 resulted in a reduction in the synergistic effect. However, in the case of pH 3, an additive effect was obtained. Moreover, the effect of the pH on the regeneration of α-tocopherol by rosmarinic acid in heterogeneous Tween 20 solutions was studied using EPR spectrometer. The same was true for the regeneration efficiency, where the reaction at pH 7 exhibited the highest regeneration efficiency of 0.3 mol of α-tocopheroxyl radicals reduced/mol of phenolics. However, the study on depletions of rosmarinic acid and α-tocopherol revealed that the formation of caffeic acid, an oxidative degradation product of rosmarinic acid, could be involved in enhancing the antioxidant activity observed at pH 7 rather than the antioxidant regeneration. This study has highlighted that the importance of pH-dependent antioxidant interactions does not solely rely on antioxidant regeneration. In addition, the formation of other oxidative products from an antioxidant should be taken into account.
authors: Department of Agro-Industry Technology and Management, Faculty of Agro-Industry, King Mongkut's University of Technology North Bangkok , Bangkok 10800, Thailand.
authors: Ketinun
authors: K
authors: Kittipongpittaya
authors: Food Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC) , 113 Thailand Science Park, Phaholyothin Road, Khlong Nueng, Khlong Luang, Pathumthani 12120, Thailand.
authors: Atikorn
authors: A
authors: Panya
authors: Food Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC) , 113 Thailand Science Park, Phaholyothin Road, Khlong Nueng, Khlong Luang, Pathumthani 12120, Thailand.
authors: Natthaporn
authors: N
authors: Phonsatta
authors: Department of Food Science, Chenoweth Laboratory, University of Massachusetts , 100 Holdsworth Way, Amherst, Massachusetts 01003, United States.|Bioactive Natural Products Research Group, Department of Biochemistry, Faculty of Science, King Abdulaziz University , P.O. Box 80203, Jeddah 21589, Saudi Arabia.
authors: Eric A
authors: EA
authors: Decker
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D002934:Cinnamates / Q000737:chemistry*; D053630:Depsides / Q000737:chemistry*; D004655:Emulsions / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009821:Oils / Q000737:chemistry*; D010084:Oxidation-Reduction; D014867:Water / Q000737:chemistry*; D024502:alpha-Tocopherol / Q000737:chemistry*; D000097123:Rosmarinic Acid
chemical_list: D000975:Antioxidants; D002934:Cinnamates; D053630:Depsides; D004655:Emulsions; D009821:Oils; D014867:Water; D024502:alpha-Tocopherol; D000097123:Rosmarinic Acid
keywords: antioxidant interaction; regeneration; rosmarinic acid; α-tocopherol