title: Antioxidant capacity of (+)-catechin visible-light photoirradiated in the presence of vitamin B2.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.affiliation: a Unidad Académica Río Gallegos, Universidad Nacional de la Patagonia Austral , Santa Cruz , Argentina.
authors.forename: M G
authors.identifier: http://orcid.org/0000-0002-7341-4162
authors.initials: MG
authors.lastname: Barua
authors.affiliation: a Unidad Académica Río Gallegos, Universidad Nacional de la Patagonia Austral , Santa Cruz , Argentina.
authors.forename: J P
authors.identifier: http://orcid.org/0000-0002-9822-9844
authors.initials: JP
authors.lastname: Escalada
authors.affiliation: a Unidad Académica Río Gallegos, Universidad Nacional de la Patagonia Austral , Santa Cruz , Argentina.
authors.forename: M
authors.identifier: http://orcid.org/0000-0002-0354-9424
authors.initials: M
authors.lastname: Bregliani
authors.affiliation: a Unidad Académica Río Gallegos, Universidad Nacional de la Patagonia Austral , Santa Cruz , Argentina.
authors.forename: A
authors.identifier: http://orcid.org/0000-0003-4772-9184
authors.initials: A
authors.lastname: Pajares
authors.affiliation: b Departamento de Química , Universidad Nacional de Río Cuarto , Córdoba , Argentina.
authors.forename: S
authors.initials: S
authors.lastname: Criado
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D002392:Catechin / Q000737:chemistry*; D008027:Light; D017319:Photosensitizing Agents / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000737:chemistry; D012256:Riboflavin / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D017319:Photosensitizing Agents; D017382:Reactive Oxygen Species; D002392:Catechin; D012256:Riboflavin
keywords: Antioxidants; catechins; photodegradation; reactive oxygen species; riboflavin; vitamin B2