Preparation, identification and their antitumor activities in vitro of polysaccharides from Chlorella pyrenoidosa

Ultrafiltration membranes of different pore size were applied to fractionate Chlorella pyrenoidosa polysaccharides (CPPS) and the main fraction could be separated by a membrane with nominal molecular weight cut-off (NMWCO) of 30 kDa. Ultrafiltration parameters of 40 degrees C 14.0 psi were optimized for obtaining the main fraction. The resulting sample was further purified by anion-exchange chromatography and size exclusion chromatography, and two distinctive polysaccharides, CPPS la and IIa were recovered. CPPS IIa had infrared spectral characteristic of polysaccharides similar to CPPS la, and the symmetrical stretching peak at 1408-1382 cm(-1) was an indication of the presence of carboxyl groups. The peak molecular weights were 69658 Da and 109406 Da, for CPPS la and CPPS IIa, respectively. Both CPPS la and IIa were composed of rhamnose.. mannose, glucose, galactose and an unknown monosaccharide. Galactose (relative mass 46.5%) was the predominant monosaccharide of CPPS la and in UPS IIa, rhamnose (37.8%) was predominant. CPPS la and IIa presented significantly higher antitumor activity against A549 in vitro than did a blank control, in a dose-dependent manner. Both fractions might be useful for developing natural safe antitumor drugs from C pyrenoidosa resources. (c) 2007 Elsevier Ltd. All rights reserved.