TY - JOUR
T1 - Isomerization of cholecalciferol through energy transfer as a protective mechanism against flavin-sensitized photooxidation
AU - Sccurachio, Regina S
AU - Santos, Willy G.
AU - do Nascimento, Eduardo S.P.
AU - Skibsted, Leif Horsfelt
AU - Cardoso, Daniel R
PY - 2015/5/13
Y1 - 2015/5/13
N2 - Cholecalciferol, vitamin D3, was found to isomerize to 5,6-trans-vitamin-D3 with a quantum yield of 0.15 ± 0.01 in air-saturated 7/3 tert-butyl alcohol/water (v/v) at 25 °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 × 108 L mol-1 s-1 in 7/3 tert-butyl alcohol/water (v/v) at 25 °C, assigned to energy transfer from 3FMN∗ to form a reactive vit.D3 diradical. vit.D3 forms a 1/1 precomplex with FMN by hydrophobic stacking with ΔH° = -36 ± 7 kJ mol-1 and ΔS° = -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.
AB - Cholecalciferol, vitamin D3, was found to isomerize to 5,6-trans-vitamin-D3 with a quantum yield of 0.15 ± 0.01 in air-saturated 7/3 tert-butyl alcohol/water (v/v) at 25 °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 × 108 L mol-1 s-1 in 7/3 tert-butyl alcohol/water (v/v) at 25 °C, assigned to energy transfer from 3FMN∗ to form a reactive vit.D3 diradical. vit.D3 forms a 1/1 precomplex with FMN by hydrophobic stacking with ΔH° = -36 ± 7 kJ mol-1 and ΔS° = -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.
U2 - 10.1021/jf505958c
DO - 10.1021/jf505958c
M3 - Journal article
C2 - 25891983
SN - 0021-8561
VL - 63
SP - 4629
EP - 4637
JO - Journal of Agricultural and Food Chemistry
JF - Journal of Agricultural and Food Chemistry
IS - 18
ER -