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Composition of tomatoes and tomato products in antioxidants (WG1) page 64
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Carotenoid λmax (nm) Ε 1%
5-cis-lycopene 362 443 470 502 3466
7-cis-lycopene 362 443 470 502 2901
15-cis-lycopene 362 443 470 502 2072
13-cis lycopene 360 437 463 494 -
9-cis-lycopene 360 438 464 495 -
7,9,7’,9’-cis-lycopene - 414 436 463
Table 23 Spectrophotometric parameters of cis isomers of lycopene
(in hexane containing 2% (v/v) dichloromethane or toluene), main maxima are underlined
From Hengartner et al. 1992; Aebisher et al. 1999; Giger 1994; Schierle et al. 1997
Cis isomers tend to cristallize or aggregate much less easily than all-trans isomers, this
improves their solubility in lipophilic organic solvants.
7.1.4 Antioxidant properties
7.1.4.1 Quenching of singlet oxygen
Because of its highly unsaturated structure, lycopene has the capacity of accepting
energy from various electronically excited species in particular singlet oxygen : 1 O2, thus
acting as an antioxidant molecule.
The mechanism of quenching of singlet oxygen by carotenoids (figure 9) is mainly a
physical process involving the transfer of excitation energy from singlet oxygen to the
carotenoid, resulting in ground state oxygen and excited carotenoid. In turn, the energy is
dissipated through physical interaction (rotation and vibration) between the excited carotenoid
and its surroundings, yielding ground state carotenoid and heat.
1
O2 + Carotenoid ➔ 3 O2 + 3 Carotenoid
3
Carotenoid ➔ Carotenoid + heat
Figure 9 : Physical quenching of singlet oxygen by a carotenoid