Free radical scavenging properties of phytofluene and phytoene isomers as compared to lycopene: a combined experimental and theoretical study.

Free radical scavenging properties of Lycopene (LYC), Phytofluene (PF), and Phytoene (PE) are studied experimentally, considering the electron transfer mechanism and using the ABTS(•+) decolouration assay. Density Functional Theory is used to obtain the theoretical UV-visible spectra of ABTS (neutral and cation) and to determine the free radical scavenger capacity in terms of the electron donor mechanism and the deactivation of singlet oxygen. The experimental data agreed very well with the theoretical results. Considering both mechanisms, LYC, PF, and PE can be considered good free radical scavengers, with LYC turning out to be the best and PE the worst antiradical. However, the triplets that formed following the deactivation of singlet oxygen presented similar capacity for donating electrons. In the case of triplets, the antiradical capacity of LYC, PF, and PE is similar in terms of the electron donor mechanism. Although the results indicated that PF and PE are not as effective antiradicals as LYC, which is to be expected due to the number of conjugated double bonds, they do present a higher antioxidant capacity than expected considering the small number of conjugated double bonds.