Ben-Gurion University of the Negev

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(Lee, 2002a; Archetti, 2009). Many additional possible functions have been proposed
that rely on an interaction between plants and animals (biotic factors) (Archetti, 2009):
coevolution, fruit flag, direct defense, camouflage, anticamouflage and tritrophic
mutualism.
1.2.1.1. Anthocyanins as antioxidants
Anthocyanins have been shown to function as in vivo antioxidants, effectively
neutralizing various ROS (Lee and Gould, 2002; Nagata et al., 2003; Kytridis and
Manetas, 2006). Hydrogen peroxide is the most probable target for neutralization by
anthocyanins, because it is the only ROS known to be able to penetrate both
chloroplasts, where ROS are produced, and vacuole, where anthocyanins are stored
(Ougham et al., 2005). Experiments using leaf extracts have, however, yielded
conflicting results. Neil et al. (2002a) reported that leaf extracts from red varieties of
Elatostema rugosum had higher antioxidant capacity compared to green morphs and
anthocyanins contributed to that capacity more than the other low molecular weight
antioxidants. This, however, was not the case in Quintinia serrata, where both red and
green leaf extracts displayed the same antioxidative capacities (Neil et al., 2002b).
A critical point concerning antioxidative function of anthocyanins is their cellular
localization. One could argue that effective in vivo antioxidants should reside as close as
possible to the source of oxy-radical production. However, in leaves, the illuminated
chloroplasts of the mesophyll cells are the main source of ROS (Asada, 2000), while
anthocyanins are located in the upper and/or lower epidermis (Lee and Collins, 2001).
Moreover, the intracellular location of anthocyanins is the vacuole, although colorless
tautomers appear in the cytoplasm during the transit time between their biosynthesis and
transport to the vacuole (Hrazdina et al., 1978). As much as is known, there is no report
for the presence of anthocyanins in chloroplasts (Manetas, 2006). Flavonoids and