Isomerization of Cholecalciferol through Energy Transfer as a Protective Mechanism Against Flavin-Sensitized Photooxidation

Author(s)

Scurachio, Regina S. ^[1] ; Santos, Willy G. ^[1] ; do Nascimento, Eduardo S. P. ^[1] ; Skibsted, Leif H. ; Cardoso, Daniel R. ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560470 Sao Carlos - Brazil

• Document type: Journal article
• Source: Journal of Agricultural and Food Chemistry; v. 63, n. 18, p. 4629-4637, MAY 13 2015.
• Web of Science Citations: 1

Abstract

Cholecalciferol, vitamin D-3, was found to isomerize to 5,6-trans-vitamin-D-3 with a quantum yield of 0.15 +/- 0.01 in air-saturated 7/3 tert-butyl alcohol/water (v/v) at 25 degrees C, increasing to 0.32 +/- 0.02 in the absence of oxygen, through quenching of triplet excited state flavin mononucleotide, FMN, rather than becoming oxidized. The quenching was found by laser flash photolysis to have a rate constant of 1.4 x 10(8) L mol(-1) s(-1) in 7/3 tert-butyl alcohol/water (v/v) at 25 degrees C, assigned to energy transfer from (FMN)-F-3{*} to form a reactive vit.D-3 diradical. vit.D-3 forms a 1/1 precomplex with FMN by hydrophobic stacking with Delta H degrees = -36 +/- 7 kJ mol(-1) and Delta S degrees = -4 +/- 3 J mol(-1) K-1, as shown by single photon counting fluorescence spectroscopy and steady-state fluorescence spectroscopy. Both ground-state precomplex formation and excited-state energy transfer seem important for vit.D3 protection against flavin-sensitized photooxidation of nutrients in food and biological systems. (AU)

• FAPESP's process: 11/51555-7 - Bread and meat for the future
• Grantee: Daniel Rodrigues Cardoso
• Support Opportunities: Regular Research Grants