Table.
Chemical Assessments of the Antioxidant Abilities of Tocopherols in Organic Solution and Aqueous Suspension of Phospholipids
Rates | Antioxidant Efficiencies | Fetal Resorption Assay | |||||||
---|---|---|---|---|---|---|---|---|---|
ks ·10-3M-1 s-1 | ks ·10-5 M-1 s-1 | k5 ·10-4 M-1 s-1 | K1 ·10-4 M-1 s-1 | k1 ·10-4 M-1 s-1 | |||||
[52] | [55] | [51] | [50] | [50] | [53] | [53] | [54] | [56] | |
EtOH | Triton Micelle | IAS | LKEPR | 0.10 M HDTBr | 0.10 M SDS | 0.5 M SDS | % of all rac α-tocopheryl acetate | ||
Footnotes: | {a} | {b} | {c} | {d} | {d} | {e} | {e} | {f} | {g} |
Conjugated dienes | Conjugated dienes | O2uptake | |||||||
α-Tocopherol | 5.12 | 5.12 | 235 ± 50 | 320 | 260 | 1770 ± 90 | 1830 ± 50 | 1000 | 80 |
β-Tocopherol | 2.24 | 1.05 | 166 ± 33 | 130 | 970 ± 140 | 950 ± 30 | 590 | 45 | |
γ-Tocopherol | 2.42 | 1.00 | 159 ± 42 | 140 | 70 | 1020 ± 40 | 980 ± 60 | 590 | 13 |
δ-Tocopherol | 1 | 0.149 | 65 ± 13 | 44 | 33 | 530 ± 30 | 570 ± 50 | 240 | <0.4 |
Tocol | 0.56 | 0.0353 | |||||||
PMC | 214 ± 81 | 380 | 2850 ± 100 | 2880 ± 120 | 4050 | ||||
Trolox | 110 | 8300 ± 360 | 1320 ± 90 | 2970 |
PMC = 2,3,5,7,8-pentamethylchromanol, Tocol = 2-methyl-2-(4,8,12-trimethyltridecyl)chroman-6-ol, Trolox = 6-Hydroxy-2,5,7,8- tetramethylchroman-2-carboxylic acid
ks is the second-order rate constant (in ethanol) for the H-atom abstraction of the various chromanols by the stable phenoxy radical of 3,5-di-tert-butyl-4’-methoxybiphenyl-4-ol at 25°C.
ks is the second-order rate constant (in 5% Triton X-100 micelles) for the H-atom abstraction of the various chromanols by the stable phenoxy radical of 3,5-di-tert-butyl-4’-methoxybiphenyl-4-ol at 25°C.
k5 is the second order rate constant for the H-atom abstraction of the various chromanols with peroxyradicals produced by the 2,2′-azo-bis(isobutyronitrile) (AIBN) initiated oxidation of styrene in chlorobenzene solution at 30°C
k1 is the second order rate constant for the H-atom abstraction of the various chromanols with peroxyradicals produced by AIBN initiated oxidation of styrene in chlorobenzene solution at 30°C; the so-called inhibited autoxidation of styrene (IAS) method essentially similar to that used in [51]. The laser kinetic electron paramagnetic resonance (LKEPR) method uses a laser pulse to decompose di-tert-butyl ketone in the presence of oxygen to quickly produce peroxyl radicals whose decay rate due to H-atom abstraction of the chromanols could be monitored by EPR.
Antioxidant Efficiencies (AE) are defined as kinh/kp where kinh is the second order rate constant for the reaction of peroxyl radicals from linoleic acid with the chromanols and kp is the second order propagation rate constant for the autoxidation of linoleic acid. Consequently, the AE values are without units. Linoleic acid was provided in hexadecyltrimethylammonium bromide (HDTBr) or sodium dodecylsulfate (SDS) supported micelles in the presence of the radical initiator 2,2′-azobis(2- amidinopropane) (ABAP) at pH 7.4. Rates of reactions were monitored by following conjugated diene formation at 234 nm [53] or O2-uptake [54].
Biological activities of orally provided chromanols are presented relative to all-rac-α-tocopheryl acetate (100%).