title: A comparative study of the antioxidant scavenging activity of green tea, black tea and coffee extracts: a kinetic approach.
abstract: The antioxidant activities of three beverages, coffee, black tea and green tea, along with their major components, were investigated in terms of their reaction with the stable radical 2,2'-diphenyl-2-picrylhydrazyl (DPPH). We used a kinetic approach in parallel with quantification methods based on a fixed end-point to determine the scavenging efficiency of compounds abundant in these beverages during their reaction with DPPH using a stopped-flow spectrophotometer-based method. Ascorbic acid, (+)-catechin, (-)-epigallocatechin, tannic acid, and caffeic acid were selected as model antioxidants to study in coffee, black tea and green tea. We applied a second-order model to demonstrate similarities in the kinetics behavior of beverages and related compounds. Our findings showed the slopes k2(')((mol/L)(-1)s(-1)) and k2max(')((mol/L)(1)s(-1)) exhibited similar and correlated values; we suggest the variation in k2(') as a function of time is more informative about antioxidant properties than reaction with DPPH alone. We also used IC100 to test the reliability of the relative stoichiometry using a new comparative parameter "n", which was calculated as: n=c0DPPHIC100 (mol/L(mol/L)(-1), (mol/L)mlmg(-1) or molg(-1)).
authors.affiliation: Al Akhawayn University, School of Science and Engineering, Laboratory of Biotechnology, Av. Hassan II, P.O. Box 104, Ifrane, Morocco; Université Sidi Mohamed Ben Abdellah, Faculté des Sciences Dhar el Mehrez, Laboratoire de Biotechnologie, Unité de Biotechnologie des Microorganismes, Fés, Morocco.
authors.forename: Jaouad
authors.initials: J
authors.lastname: Anissi
authors.affiliation: Université Sidi Mohamed Ben Abdellah, Faculté des Sciences Dhar el Mehrez, Laboratoire de Biotechnologie, Unité de Biotechnologie des Microorganismes, Fés, Morocco.
authors.forename: Mohammed
authors.initials: M
authors.lastname: El Hassouni
authors.affiliation: Al Akhawayn University, School of Science and Engineering, Laboratory of Biotechnology, Av. Hassan II, P.O. Box 104, Ifrane, Morocco.
authors.forename: Abdelkrim
authors.initials: A
authors.lastname: Ouardaoui
authors.affiliation: Al Akhawayn University, School of Science and Engineering, Laboratory of Biotechnology, Av. Hassan II, P.O. Box 104, Ifrane, Morocco. Electronic address: k.sendide@aui.ma.
authors.forename: Khalid
authors.initials: K
authors.lastname: Sendide
mesh_terms: D028241:Camellia sinensis / Q000737:chemistry*; D040503:Coffea / Q000737:chemistry*; D003069:Coffee / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry*; D007700:Kinetics; D010936:Plant Extracts / Q000737:chemistry*; D013662:Tea / Q000737:chemistry*
chemical_list: D003069:Coffee; D016166:Free Radical Scavengers; D010936:Plant Extracts; D013662:Tea
keywords: Black tea; Coffee; DPPH() free-radical; DPPH() scavenging efficiency comparison; Green tea; Kinetic behavior; Second-order model