Synthesize Lutein Disuccinate From High-Purity Lutein Extracted From Marigold Flowers

Lutein is a dihydroxy carotenoid with ionone ring, existing in plant tissue in the form of lutein fatty acid ester (referred to as lutein ester). It involves many enzymes, such as pancreatic lipase, pancreatic carboxylester lipase, phospholipase B, and other retinyl ester hydrolases to hydrolyze lutein esters into lutein. After intestinal absorption and subsequent transport in plasma within lipoproteins, a fraction of the lutein is transferred to the retina and functions as potent antioxidant and effective screeners of high energy blue light to contribute to risk reduction of retinal diseases such as age-related macular degeneration and cataracts. To improve the solubility and stability of lutein, lutein disuccinate was synthesized from lutein to satisfy people’s demand for lutein and succinate.The crystals with trans-lutein content90.42%were finally gained from marigold dried flower particles after extraction, saponification and purification process. N, N-diisopropylethylamine was added to catalyze the lutein crystals completely dissolving in dichloromethane to esterify with succinic anhydride. After washing and concentration, a red-orange lutein disuccinate concretes was obtained. The chemical structure of lutein disuccinate was elucidated by UV-Vis, HPLC-Mass, IR, NMR. Use quantum chemistry theory PBE density functional method to optimize molecular model of lutein and succinic anhydride before and after the reaction. The feasibility of lutein esterifying with succinic anhydride was proved from the microscopic electron density level, revealing the reaction mechanism.An method with C18as stationary phase,0.05%acetic acid in water and0.05%acetic acid in acetonitrile (5:95, V/V) as the mobile phase was used to purify lutein disuccinate. After purification, the purity of lutein disuccinate was up to97.9%, which reached the purity of standard product. An accurate and reproducible C30-HPLC quantitative method of lutein disuccinate was achieved with a binary mobile phase consisting of0.05%acetic acid in methanol:0.05%acetic acid in acetonitrile (50:50, v/v) in the linear range of200～1000ng. This economical and effective method can be used to monitor its yield during synthesis. The ultrasonic technology was introduced into the lutein disuccinate synthesis process, greatly improving the yield and shortening the reaction time. The effects of the molar ratio of acid with alcohol, ultrasonic power, ultrasonic frequency, the molar ratio of the catalyst with lutein were investigated by single factor test. Based on the single factor experiments, the effects of the molar ratio of acid with alcohol, ultrasonic power and time were optimized with Uniform Design Experiment. The result showed that the optimum synthesis parameters were as follows:the molar ratio of acid with alcohol200, ultrasonic power300W and time175min. Under the optimum conditions, the production rate of lutein disuccinate reached71.64%, which51.32%higher than that of conventional reaction. The relationship between reaction temperature and the rate of chemical reaction was tested to create the Arrhenius formula of lutein disuccinate synthesis: Lnvo=41.38-11.43/T The reaction activation energy of the reaction was71.67kJ/mol.