Lycopene light

Many organic compounds such as lycopene are colored because their HOMO-LUMO energy gap is small enough that appears m the visible range of the spec trum All that is required for a compound to be colored however is that it possess some absorption m the visible range It often happens that a compound will have its k m the UV region but that the peak is broad and extends into the visible Absorption of the blue to violet components of visible light occurs and the compound appears yellow... 

A molecule of lycopene can absorb blue light because the electrons are not orbiting a single atom, they are sloshing around orbiting many atoms, and the energy needed to move them is a lot less than in a smaller molecule, or one without conjugated bonds. 

Only 6% of the iifitial total lycopene prepared as a thin film on the surface of each vial remained after 144 hr under fluorescent light (2000 to 3000 lux) at 25°C under N2. Lycopene degradation occurred as a first-order reaction at 2.93 x 10" /min, and the concentration of aU lycopene mono-c isomers already present in the sample, 5-cis-, 9-cis-, l3-cis- and 15-d5 -, showed an inconsistent change in this period. Nevertheless, formation of lycopene di-c isomers was observed after 32 hr of light exposure and when considering relative percentage, loss of 13% of all-trani-lycopene occurred while an increase of 11% for total cis isomers was found after 144 hr. ... 

Lycopene had a protective effect on the oxidative stress-mediated damage of the human skin after irradiation with UV light (Ribaya-Mercado and others 1995). 

Fig. 3. Pump-deplete-probe spectroscopy on lycopene in hexane, a) Experimental setup After excitation and depletion of Car S2 with a delay of r=50fs, a white-light probe pulse at delay tprob<.=2ps measures the transient absorption spectrum, b) Spectra without (solid curve) and with depletion pulse (dotted) and their difference (shaded area). Only the Car Si state is depleted the ground state bleach (S0-S2) and positive absorption feature on its low energy side (hotSo-S2) are unaffected.

Carotenoids are sensitive to heat, light, acid, oxygen and chemicals. They may react in various ways during the process of isolation. The most important change is the formation of cis-isomers. Lycopene is said to form 1056 isomers (36), each with different properties. In some cases, cis-isomers separate more easily than carotenoids that differ by rearrangement of a double bond, i.e., zeaxanthin and lutein. However, a mixture of isomers can often be identified by their failure to crystallize and to give sharp separations on chromatographic columns. 

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