title: Implementation of response surface methodology to assess the antiradical behaviour in mixtures of ascorbic acid and α-tocopherol with grape (Vitis vinifera) stem extracts.
abstract: The efficiency of grape stem extracts to express antiradical activity was assessed using two different approaches and DPPH as the radical probe. In addition, the mixture effects when the extracts were combined with ascorbic acid (AA) and α-tocopherol (α-Tcp) were also evaluated. The approaches included a simple linear regression analysis between the response (antiradical activity) and concentration, but also a response surface methodology, which permitted the monitoring of the response upon simultaneous variation of both the concentration of the total polyphenols of the extracts and either of the antioxidants (AA and α-Tcp). The deployment of linear regression poses important constraints with regard to concentration ranges, whereas response surface methodology might be a valuable statistical tool for similar assessments and credible modelling of binary mixtures of antioxidants. In all combinations tested it was found that an antagonism was manifested, presumably as a result of AA and α-Tcp regeneration by the extract polyphenols, at the expense of the latter.
authors.affiliation: Department of Science of Dietetics-Nutrition, Harokopio University, 70, El. Venizelou, 17671 Kallithea, Athens, Greece.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Karvela
authors.affiliation: Department of Food Science & Nutrition, University of the Aegean, 2, Mitr. Ioakim, 81400 Myrina, Lemnos, Greece. Electronic address: dmakris@aegean.gr.
authors.forename: Dimitris P
authors.initials: DP
authors.lastname: Makris
authors.affiliation: Department of Science of Dietetics-Nutrition, Harokopio University, 70, El. Venizelou, 17671 Kallithea, Athens, Greece.
authors.forename: Vaios T
authors.initials: VT
authors.lastname: Karathanos
mesh_terms: D000975:Antioxidants; D001205:Ascorbic Acid / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*; D018547:Plant Stems / Q000737:chemistry*; D059808:Polyphenols / Q000032:analysis / Q000737:chemistry*; D013678:Technology, Pharmaceutical / Q000379:methods*; D027843:Vitis; D024502:alpha-Tocopherol / Q000032:analysis / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D010936:Plant Extracts; D059808:Polyphenols; D024502:alpha-Tocopherol; D001205:Ascorbic Acid
keywords: AA; Antagonism; Antioxidants; Grape stems; ME; Polyphenols; Response surface methodology; TP; ascorbic acid; mixture effect; total polyphenols expressed as mg gallic acid equivalentsL(−1); α-Tcp; α-tocopherol