Photodegradation of Folate Sensitized by Riboflavin

Author(s)

Scurachio, Regina S. ^[1] ; Skibsted, Leif H. ^[2] ; Metzker, Gustavo ^[1] ; Cardoso, Daniel R. ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Quim Sao Carlos, Sao Paulo - Brazil

^[2] Univ Copenhagen, Dept Food Sci, Fac Life Sci, Frederiksberg C - Denmark

• Document type: Journal article
• Source: Photochemistry and Photobiology; v. 87, n. 4, p. 840-845, JUL-AUG 2011.
• Web of Science Citations: 12

Abstract

Folate is shown to react with singlet-excited state of riboflavin in a diffusion controlled reaction and with triplet-excited state of riboflavin in a somewhat slower reaction with (3)k(q) = 4.8 x 10(8) L mol(-1) s(-1) in aqueous phosphate buffer at pH 7.4, ionic strength of 0.2 mol L(-1), and 25 degrees C. Singlet quenching is assigned as photo-induced reductive electron transfer from ground state folate to singlet-excited riboflavin, while triplet quenching is assigned as one-electron transfer rather than hydrogen atom transfer from folate to triplet-excited riboflavin, as the reaction quantum yield, phi = 0.32, is hardly influenced by solvent change from water to deuterium oxide, phi = 0.37. Cyclic voltammetry showed an irreversible two-electron anodic process for folate, E = 1.14 V versus NHE at a scan-rate of 50 mV s(-1), which appears to be kinetically controlled by the heterogeneous electron transfer from the substrates to the electrode. Main products of folate photooxidation sensitized by riboflavin were pterin-6-carboxylic acid and p-aminobenzoyl-L-glutamic acid as shown by liquid chromatographic ion-trap mass spectrometry (LC-IT-MS). (AU)

• FAPESP's process: 09/00858-0 - Mechanism and consequences of redox process in food: Chemical and Photochemical aspects of the oxidative deterioration and antioxidant activity of beer and dairy products
• Grantee: Daniel Rodrigues Cardoso
• Support Opportunities: Regular Research Grants