Study of antioxidant activities of sulfated polysaccharides from Laminaria japonica |
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Authors: | Xue Zhao Chang-Hu Xue Ba-Fang Li |
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Institution: | (1) College of Food Science and Technology, Ocean University of China, No.5, Yu Shan Road, Qingdao, Shandong Province, 266003, People’s Republic of China |
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Abstract: | The composition, molecular weight and in vitro antioxidant activity of various sulfated polysaccharides obtained by anion
exchange chromatography, acid hydrolysis and radical process degradation of the crude sulfated polysaccharide extracted from
Laminaria japonica were compared. The low sulfated F-A2, with a peak-molecular weight (Mp) of 5–15 kDa, 14.5% sulfated ester and 21.8% glucuronic
acid, exhibited a very strong antioxidant activity on superoxide and hydroxyl radicals, with activity even higher than that
of large molecular weight fractions F-A and F-B. However, highly sulfated fractions with a peak-molecular weight below 15 kDa
had much lower antioxidant activities than other fractions. These results indicated that the sulfate group of the low molecular
weight fractions represents a physical block for the reaction with oxygen radicals. The chemical properties and antioxidant
activities of sulfated polysaccharide fractions obtained by radical process degradation of crude sulfated polysaccharide were
quite different from those obtained by acid hydrolysates. By radical process degradation, the high molecular weight was decreased
to give LM2 (Mp 8 kDa) and LM1 (Mp 1.5 kDa), with a yield of 40% and 15%, respectively. LM2 was enriched with fucose and sulfated
ester, while containing low amounts of glucuronic acid. The antioxidant activity showed that LM2 was unable to scavenge either
superoxide or hydroxyl radical, which suggested that radical process degradation targeted mainly ascopyllan-like species rich
in glucuronic acid, while the fraction rich in sulfated l-fucose remained unchanged. However, LM1 with Mp 1.5 kDa still retained apparent scavenging ability for superoxide radical,
although it contained no glucuronic acid and certain amounts of galactose and mannose as main neutral sugars. These result
suggest that the antioxidant activity of sulfated polysaccharides is apparently related not only to molecular weight and sulfated
ester content, as previously determined, but also to glucuronic acid and fucose content. |
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Keywords: | Laminaria japonica Sulfated polysaccharide Free radical Antioxidant Radical process degradation |
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