M G Barua1, J P Escalada1, M Bregliani1, A Pajares1, S Criado2. 1. a Unidad Académica Río Gallegos, Universidad Nacional de la Patagonia Austral , Santa Cruz , Argentina. 2. b Departamento de Química , Universidad Nacional de Río Cuarto , Córdoba , Argentina.
Abstract
OBJECTIVES: Catechins are important components of human diet and have received special attention due to their antioxidant capacity. The purpose of this paper was to study the antioxidant action of (+)-catechin (CTQ) in the presence of vitamin B2 (riboflavin) as light-absorbing agent. Furthermore, two model compounds, catechol (CTC) and resorcinol (RSC), were selected in order to elucidate the reactive target of the CTQ molecule. The influence of pH-medium was investigated. METHODS: Stationary photolysis, polarographic detection of dissolved oxygen, reactive oxygen species (ROS)-scavengers, time-resolved near-IR phosphorescence detection, stationary, and time-resolved fluorescence and laser flash photolysis techniques were employed. RESULTS: CTQ interacts with riboflavin under visible-light photoirradiation as well as with different ROS which are generated in this mechanism. Radical-scavenging activity increases with increasing of pH-medium. DISCUSSION: pH-effect of the medium on radical-scavenging activity comes from the increased electron-donating ability of CTQ upon deprotonation. These results are very interesting due to the fact that the pH of the food products displays important variations. The [Formula: see text]-scavenging ability of CTQ, would be equal to the additive contribution of each reactive center, CTC, and RSC, present at the molecule of CTQ. However, CTQ would have a moderate ability to removal of [Formula: see text]-species at pH 7.
OBJECTIVES:Catechins are important components of human diet and have received special attention due to their antioxidant capacity. The purpose of this paper was to study the antioxidant action of (+)-catechin (CTQ) in the presence of vitamin B2 (riboflavin) as light-absorbing agent. Furthermore, two model compounds, catechol (CTC) and resorcinol (RSC), were selected in order to elucidate the reactive target of the CTQ molecule. The influence of pH-medium was investigated. METHODS: Stationary photolysis, polarographic detection of dissolved oxygen, reactive oxygen species (ROS)-scavengers, time-resolved near-IR phosphorescence detection, stationary, and time-resolved fluorescence and laser flash photolysis techniques were employed. RESULTS:CTQ interacts with riboflavin under visible-light photoirradiation as well as with different ROS which are generated in this mechanism. Radical-scavenging activity increases with increasing of pH-medium. DISCUSSION: pH-effect of the medium on radical-scavenging activity comes from the increased electron-donating ability of CTQ upon deprotonation. These results are very interesting due to the fact that the pH of the food products displays important variations. The [Formula: see text]-scavenging ability of CTQ, would be equal to the additive contribution of each reactive center, CTC, and RSC, present at the molecule of CTQ. However, CTQ would have a moderate ability to removal of [Formula: see text]-species at pH 7.
Authors: María P Montaña; Walter A Massad; Susana Criado; Alicia Biasutti; Norman A García Journal: Photochem Photobiol Date: 2010-06-07 Impact factor: 3.421
Authors: Juan P Escalada; Adriana Pajares; José Gianotti; Alicia Biasutti; Susana Criado; Patricia Molina; Walter Massad; Francisco Amat-Guerri; Norman A García Journal: J Hazard Mater Date: 2010-11-12 Impact factor: 10.588
Authors: Eduardo Silva; Leonardo Herrera; Ana María Edwards; Julio de la Fuente; Eduardo Lissi Journal: Photochem Photobiol Date: 2005 Jan-Feb Impact factor: 3.421