Abstract:
Objective Extraction of polysaccharides from Shifocui tea leaves harvested in summer and autumn were optimized and antioxidant activity of CSTP-1 and CSTP-2 fractions determined.
Method Based upon polysaccharide extraction rate, conditions of the process were optimized by an experiment using the single factor and response surface methods. Purified polysaccharide fractions, CSTP-1 and CSTP-2 were obtained by CL-4B column chromatography on an agarose gel, and contents determined by phenol sulfuric acid and m-hydroxybiphenyl methods, molecular weight by HPLC, and antioxidant activities by scavenging rates on free radicals, DPPH· , · OH, and O2−.
Results The optimized extraction process applied a liquid to solid ratio of 23:1 (mL·g−1) at 71.6℃ for 4.2 h to yield 1.31% of CSTP. The obtained homogeneous polysaccharides were CSTP-1 with a molecular weight of 9.23×105 Da and CSTP-2 with a molecular weight of 4.56×104 Da. The optimization significantly increased uronic acids, especially neutral sugar in CSTP-1. Both fractions of the polysaccharides were glycoprotein conjugates containing pyran rings with some structural differentiations between them, as shown by infrared spectroscopy. The free radical scavenging ability of CSTP-2 was higher than that of CSTP-1, and the activity on ·OH at 800 µg·mL−1 was comparable to Vc.
Conclusion The optimized polysaccharide extraction, separation, and purification developed under this study seemed highly plausible to be used for producing functional foods that would conceivably extend the utilization of Shifucui tea.