Preparation of polysaccharides from cyanobacteria Nostoc commune and their antioxidant activities.

In this study, water soluble polysaccharides were prepared from cyanobacteria Nostoc commune by water extraction. Factors affecting the polysaccharide yields were investigated, and the optimum extraction conditions were determined as follows: time, 4h; temperature, 90 °C; the ratio of liquid to solid, 60:1 (v/w); and extraction times, 4. The extract was filtered, concentrated to ∼10% (w/v), precipitated with 3 volumes of ethanol, freeze-dried, and ground to yield a water soluble power. The polysaccharide content of the product was 96.7%, and the yield was 9.18% (w/w). Fourier transform infrared spectra demonstrated that the product samples were mainly composed of polysaccharides. The polysaccharides showed high hydroxyl radical scavenging activity (92.71%) and reducing capacity (0.445) at the concentration of 10 mg/mL.