Understanding oxidation processes in foods - Oxidation in Foods and Beverages and Antioxidant Applications - page 26

Table 1.5 Physico-chemical properties of carotenoids in comparison with -tocopherol and ascorbic acid a

1 O 2 quenching

Relative tendency d Car ·+ /diadzein 2ÿ R d R a Phenoxyl Eë

k 2 (l mol ÿ1 s ÿ1 ) b to form car ·+ V vs. NHE e k 2 (l mol ÿ1 s ÿ1 ) f scavenging

Relative rate c

4.6 10 9 5.8 10 9 -carotene 1.40 0.46 1 1 0.84

6.8 10 9 8.3 10 9 zeaxanthin 1.44 0.49 0.79 10 0.85

11.2 10 9 5.7 10 10 canthaxanthin 1.93 0.82 ~0 0.95

9.9 10 9 9.2 10 10 astaxanthin 2.10 0.94 ~0 3 0.97

6.9 10 9 lycopene 1.66 8 0.81

2.7 10 7 -tocopherol 0.31 0.15 0.80

ascorbate 1.29 0.11 0.22

a

R d ! ÿ /! ÿ Na and R a ! /! F relative to sodium and fluor, respectively. ! ÿ = (3I + A) 2 /16 (I-A) and ! = (I + 3A) 2 /16 (I-A) is based on I, the (vertical) ionization
energy, and A, the (vertical) electron affinity. From Martinez et al. (2008).
b

Second-order rate constant at 25 ëC. From Min and Boff (2002).

c

In di-tert-butyl peroxide/benzene (7/3, v/v) at 20 ëC, phenoxyl radical generated photochemically. From Mortensen and Skibsted (1997).

d

Laser flash photolysis in CHCl 3 (490 nm, 120 fs pulses). From Han et al. (2002).

e

Standard reduction potential of one-electron oxidized antioxidant, for car ·+ determined in CH 2 Cl 2 , for oxidized -tocopherol in DMF, and for the ascorbyl radical in
water. From Han et al. (2002) and Jùrgensen and Skibsted (1998).
f

Bimolecular regeneration of carotenoid by the isoflavonoid dianion in methanol/chloroform (1/10) at 25 ëC. From Han et al. (2010).