We present a density functional theory (DFT) and time-dependent density functional theory (TD-DFT) study on the stability, antioxidant properties with respect to the single electron transfer mechanism, and electronic absorption spectra of some isomers (9-cis, 13-cis, and 15-cis) of carotenoids such as astaxanthin, lycopene, and those present in virgin olive oil (lutein, beta-carotene, neoxanthin, antheraxanthin, violaxanthin, neochrome, luteoxanthin, mutatoxanthin, and violaxanthin). In general, the calculated relative stability of the cis isomers appears to be in line with experimental observations. It is predicted that the above mentioned carotenoids (cis and trans isomers) will transfer one electron to the (OH)-O-center dot radical. However, this transference is not plausible with radicals such as (OOH)-O-center dot, (OC2H5)-O-center dot, (OOC2H5)-O-center dot, (NO2)-N-center dot and (OOCH2CH)-O-center dot=CH2. On the other hand, some carotenoids (beta-carotene, lycopene, lutein, astaxanthin, violaxanthin, and antheraxanthin) will likely accept, in a medium of low polarity, one electron from the radical O-center dot(2)-. However, neoxanthin, auroxanthin, mutatoxanthin, luteoxanthin, and neochrome would not participate in such an electronic transfer mechanism. The TD-DFT studies show that neutral species of the cis and trans isomers maintain the same color. On the contrary, the ionic species undergo a "bleaching" process where the absorption wavelengths shift to longer values (>700 nm). Additionally, the formation of a complex between astaxanthin and Cu2+ is explored as well as the effect that the metal atom will have in the UV-vis spectrum.