(684c) Investigation of the Polymorphy Phenomenon of the Carotene Lutein

Carotene is a special group of hydrocarbon pigments characterized with Ï€-Ï€ conjugated double bonds in the molecular backbone. This group of compounds is supposed to have great potential in pharmaceutical, healthcare and optical materials because of its excellent properties in antioxidative, light-harvesting, photo-protective, and conductive. Carotene is unstable, due to the conjugated double bonds intend to abstract electron by photo-oxidation. Several methods such as encapsulation have been employed to enhance the stability of carotene. However, seldom studies concerned crystal engineering of carotene to improve its stability has been reported. Nonetheless, H and J aggregation phenomenon of carotene moleculars have been investigated with specific solvents. Recently, β-carotene were reported to have the ability to bind decanuclear homo-and heterometal chain through μ₁₀-briding Ï€-coordination. These findings suggested that the Ï€-Ï€ conjugated bond in carotene molecular might have strong plasticity in molecular self-assembling process. As a member of the carotene family, lutein also posseses two hydroxy group (which is easy to occurs polymorph due to the H-bonds between molecular chains) in the molecular structure besides the conjugated double bonds.Thus, cooling crystallization, diffusion zone process and vapor diffusion crystallization methods with selected solvents were tested for lutein, and crystal powders of lutein with needle like, platelet and pyramids morphylogy were obtained. By XRD, TG and DSC analyzing, three crystalline polymorphic forms of lutein were identified. The three crystalline forms of lutein exhibited distinct characters in morphylogy and stability, and the correlation between the stability and the crystal form will be investigated further.