Lutein is one of over 600 known naturally occurring carotenoids. Found in green leafy vegetables such as spinach and kale, lutein is employed by organisms as an antioxidant and for blue light absorption. Lutein is present in the plant as fatty-acid ester, with one or two fatty acids bound to the two hydroxyl-groups. Saponification of lutein esters yields lutein in approximately a 1:2 molar ratio. Lutein is also found in egg yolks, animal fats and the corpus luteum. Lutein is a lipophilic molecule and is generally insoluble in water. The presence of the long chromophore of conjugated double bonds (polyene chain) provides the distinctive light-absorbing properties. The polyene chain is susceptible to oxidative degradation by light or heat and is chemically unstable in acids.