Abstract:

Objective: To the study physico-chemical characteristics and antioxidant activities of acidic polysaccharide
extracted from Cyanobacteria from the Chaohu Lake. Methods: Acidic polysaccharide was extracted by hot water (60 ℃)
from Cyanobacteria. After deproteinization by ammonium sulfate method, the neutral and acidic polysaccharides were
pooled from the elutes of DEAE-52 gel column. Then, the acidic polysaccharides were further loaded onto Sephadex G-150
column and a purified acidic polysaccharide, CHAP, was obtained. HPLC, UV, IR, and IC were used for the analysis of
CHAP for purity, molecular weight, monosaccharide composition, spectroscopic characteristics and antioxidant activity.
Results: The CHAP obtained contained 91.49% polysaccharides and 0.18% proteins without the presence of nucleic
acids. The mean molecular weight of CHAP was 2.209 × 105 D. The monosaccharide composition of CHAP included
L-arabinose (6.36%), glucose (35.47%), D (+) xylose (5.03%), D-mannose (27.36%), D-galactose (17.09%), and unknown
monosaccharides. Infrared spectrum showed that CHAP was mainly composed of pyranose-polysaccharides and had a
characteristic absorption peak of α-D-galactopyranosyl. The results of antioxidant activity indicated that CHAP had a strong
ability to scavenge both superoxide anion free radicals and DPPH free radicals, with IC50 values of 186.05 and 276 μg/mL,
respectively. However, almost no scavenging effect against hydroxyl free radical was observed.

Key words: Cyanobacteria from the Chaohu Lake, acidic polysaccharide, physico-chemical characteristics, antioxidant activity