| Pumpkin (Cucurbiat moschata Duch) is the fruit of cucurbitaceous plants. Due to its easy growth, high yield, long shelf life and abundant nutriments, pumpkin is very popular in China. In this study, Chinese Huanglang pumpkin was selected as raw material. After the composition analysis of the natural food yellow pigment extracted from the pumpkin powder, the result indicated that there were three major carotenoids: a -carotene, B -carotene and lutein. Lutein can effectively reduce the risks of age-related macular degeneration (AMD). By filtering blue light and quenching free radicals, lutein protects against cataracts and cancers. The extraction processing of pumpkin yellow pigment from pumpkin powder was optimized. Besides, a simple method for isolation and purification of lutein from pumpkin yellow pigment was developed. The stabilities of the pigment were conducted. To testify its function, the scavenging free radical activities were evaluated. All the studies provide the basic theory for the general utilization of pumpkin. The results were shown as follows:First of all, the extractability of 9 organic solvents were compared by the wavelengh scanning. The sequence from the better to the worse was: tetrahydrofuran (THF) > chloroform > dichloroform > ethanol > ethyl ether > benzene > petroleum ether > cyclohexane > acetone. Furthermore, when ethanol was added to THF, the OD450nm value of the extract increased rapidly. Taking the factors of temperature, organic agent and ratio of material and solvent for combined experiment, the best extraction processing was as follows: THF-EtOH (3:1,v/v) as solvent, temperature at 20℃, ratio at 1:5. Ultrasonic processing for 40min, repeating for 5 times, can improve the extraction processing. Evaporating solvent of the extract at low temperature (<40℃), the last yield of pumpkin yellow pigment was 4.94%.After saponification of the pigment, the extract was analysed by HPLC.The HPLC system used throughout this study consist of a Waters 510 pump (Waters, Milford, MA), a sample injector with a 20ul loop, and a Waters 996 photodiode array detector, Millenium chromatography data system. The column used was a reversed phase ultrasphere C18 column. The mobile phase was methanol/dicholomethane/acetonitrile/water (38:32:29:1,v/v), and the flow rate was 0.6ml/min. The fluent was monitored at 450nm. The chromatography showed that there were three carotenoids: a -carotene, b -carotene and lutein. The contents of lutein and B -carotene in the pigment were 27.364mg/g and 6.802mg/g respectively. Due to the solubility of lutein in hexane, lutein was isolated and purified from the saponified extract. By HPLC analysis, the average yield of lutein was 85.4% and the purity was 92.5%.The pigment was stable to pH, preservatives, temperature not more than 100癈 and most metal ions. When there was Fe3+, it was destroyed badly. Otherwise, Ba2+ can produce the undefined precipitate. The pigment was sensitive to sunlight and high temperature (>100癈). Spectrophotometer measuring, the total content of caroteinoids in saponified product was 29.22%, and in the crude extract was 5.07%.Using VC-CUSO4-H2O2 system to study its scavenging activity, the result indicated that both the saponified extract and the purified lutein could quench the hydroxyl radical ( OH). The best concentration of scavenging was 0.2mg/ml. In the lipid self-oxidation experiment, the product showed a strong inhibition of oxidant at low concentration (<0.2%). Furthermore, VC can enhance the antioxidant ability of the pigment.In general, pumpkin yellow pigment was natural carotenoids. Extracting the pigment from pumpkin powder, especially isolation and purification of lutein, provide a new way for developing pumpkin products.
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