| The okra plant, Abelmoschus esculentus (L.) Moench, an annual herb which belongs to the family of Malvaceae, is original in Africa. Okra was introduced to China in the early of1990s and now widely cultivated in many areas. Its fruits are rich in nutrients and phytochemicals and are commonly used in traditional medicine. Due to its potential economic value and profound social significance, chinese should pay great attention on its systematic study and deep exploitation regarding its bioactive constituents.Objectives:To study on extraction, separation and content determination of polysaccharide of okra, general physical and chemical properties, structure analysis and antioxidant activity in vitro.Methods:1. The polysaccharides content of the okra plant was determined by the anthrone-sulfuric acid method.2. The protein was removed by Sevag method, TCA method and TCA-butanol method at first and then the decolorization process used by activated carbon and hydrogen peroxide was also studied. The DEAE-Cellulose52column was used to further purify the okra polysaccharides.3. By solubility determination, anthrone-sulfuric acid reaction, Coomassie Brilliant Blue reaction, iodine-potassium iodide reaction and ferric trichloride reaction, general physical and chemical properties of okra polysaccharides were assayed, and their structures were analyzed by U V, IR.4. By adopting Fenton reaction system for measuring hydroxyl radicals (·OH) clearance, pyrogallol autoxidation method for determining superoxide anion free radicals (O2-·) clearance,1,1-dipheny-2-picrylhy-drazyl (DPPH) oxidation method for measuring the DPPH free radicals (DPPH·) clearance, the reducing power and the inhibition of the polysaccharides (RPS, RPS-1, RPS-2, RPS-3) to the peroxidation of polyunsaturated fatty acid from yolk lipoprotein induced by Fe2+, the antioxidant activities in vitro were evaluated. Results:The polysacharides content of the okra plant was11.231％；The TCA-butanol method had a better effect to remove protein,and the amount of protein removed was73.05％while polysaccharides remained83.74％during the deproteinization process； and it was the activated carbon attaching process that had the most effect in decolorizing the polysaccharides,the decolouration rate was about86.25％while polysaccharides retention rate was66.07％.Three factions(RPS-1,RPS-2and RPS-3) were obtained after DEAE-Cellulose52chromatography,they are an white-floc, soluble in water,insoluble in absolute ethyl alcohol,acetone and other organic solvents,and anthrone-sulfuric acid reaction was positive,Coomassie Brilliant Blue reaction,iodine-potassium iodide reaction and ferric trichloride reaction were all negative.Analysis of UV, IR showed that RPS-1,RPS-2and RPS-3were B-heteromorphic acid nonprotein polysaccharides with acetyl amino；RPS,RPS-1, RPS-2and RPS-3showed stronger scavenging abilities against·OH and DPPH.than O2-·,and they owed certain reducing power and good ability of anti-lipid peroxidation. RPS showed stronger antioxidant activities in vitro than RPS-1,RPS-2,RPS-3while the latter three’s activity on each index were not completely the same.In addition, antioxidant activities in vitro of the samples had certain dosage-dependent.Conclusions:RPS-1,RPS-2and RPS-3were β-heteromorphic acid polysaccharides with acetyl amino,while no protein,no starch and polyphenols included；RPS,RPS-1, RPS-2and RPS-3all showed certain antioxidant activities in vitro. |
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