Isolation And Functional Study Of Lutein-Protein Complexes From Chlorella Vulgaris

Lutein, a kind of oxycarotenoid which is widely distributed in dark green leafy plants and algas, possesses significant functions such as antioxidant, vision protection, anti-cancer and atherosclerosis preventing. Because of their hydrophobic nature, luteins in plant and animal cells are found in association with lipid-protein complexes to maintain stability and exert their physiological functions. In higher plants and green alages, luteins are associated with chlorophyll-binding proteins to form light-harvesting complexes and play roles in photosynthesis.Algas such as chlorella, which contains 0.2-0.8% lutein. have more and more advantages of being the major sources to extract lutein for their short cycle, high yield and easy to culture in large scale. The objectives of this research are to isolate the natural lutein-protein complexes from chlorella and evaluate the antioxidant properties.Two kinds of lutein-protein complexes LCLPC and HCLPC were finally isolated. The isolation procedure contained solubilization of thylakoid proteins by CHAPS, anion exchange chromatography and gel filtration chromatography. The optics characteristic was analyzed by wavelength scanning. LCLPC possessed a lutein:Chl:protein ratio of about 9.72:0.35:100 (w/w/w) while this ratio in HCLPC was 11.39:6.96:100 according to HPLC and spectrophotometry analysis.The research on scavenging activity against ABTS and DPPH radical, lipid peroxidation inhibition acticity, ferrous ion-chelating activity and reducing power showed that LCLPC and HCLPC had antioxidative effects in vitro to different degrees. The antioxidant activity of the complexes was evaluated in vivo also. The rats were given CCl4 after the complexes treatment for 10 d to induce lipid peroxidation in liver and then related indicators were measured. The CCl4 treatment increased the ALT, AST levels in serum, MDA level in liver and liver index, and also decreased the SOD, CAT and GSH-PX activities in liver. Pretreatment of the complexes with different doses (100 mg/kg BW,50 mg/kg BW) decreased the elevated ALT, AST, MDA levels and liver index and also increased the reduced antioxidant enzyme activities. The results of animal experiment showed that LCLPC and HCLPC could decrease the lipid peroxidation and increase the antioxidant defense system activity in the CCl4-treated rats.Another lutein-protein complex LPC was purified from the crude pigment protein complexes extracted by Tween-20. The purification procedure contained ammonium sulfate precipitation, anion exchange chromatography and gel filtration chromatography. The molecular weight of the peptide component of LPC was 29.0 kDa. The lutein content of the complex was quantified by HPLC. LPC possessed a lutein:protein ratio of about 6.34:100 (w/w), which mean that there were three lutein molecules binding to a protein. The complex showed strong ABTS radical scavenging activity with a half elimination concentration of about 77.7 μg/mL.