| The antioxidant activity of two-year-old, three-year-old and four-year-old Aloe vera and a free racidal avtivity of antioxidant extraction by supercritical fluid of CO2 were studied by DPPH, ABTS and linoleic acid system. The aloe polysaccharides were made by ethanol precipitated and adjusted pH and the imminomodulatory activity of aloe polysaccharides were determined by delayed type of hypersensitivity (DTH) response, haemmaglutination titre(HT) and phagocytosis. The results were shown as follows:The polysaccharide and flavonoids of two-year-old, three-year-old and four-year-old Aloe vera were determined and their antioxidant activity were evaluated compared to BHT and ct-tocopherol by DPPH radical scavenging method and linoleic acid system. The results showed that three-year-old Aloe vera contained significantly higher polysaccharide and flavonoids than two-year-old Aloe vera and four-year-old Aloe vera and no significant difference of polysaccharide was found between three-year-old and four-year-old Aloe vera.. All the aloe extracts show significant antioxidant activity. The antioxidant activity of Aloe vera extracts and reference compounds followed the order: three-year-old Aloe vera > BHT > four-year-old Aloe vera > a-tocopherol > two-year-old Aloe vera. The three-year-old extract exhibited the strongest scavenging activity of 72.19%, which is significantly higher than BHT at 70.52% and a-tocopherol at 65.20%. These data suggested growth period plays a vital role on the composition and antioxidant activity of Aloe vera.The free radical scavenging activities of extracts of Aloe vera of leaf skin by supercritical CO2 extraction and solvent extraction were determined. An orthogonal array design matrix of L9 (34) was considered to optimize supercritical carbon dioxide extraction processing at a CO2flow rate of 12-36 L h-1, 35-45 Mpa, 32-50 C and 0-20% methanol. The optimum extracted yield of 1.47% was provided at 50 C , 36 L h-1, 35 MPa and 20% of modifier of methanol. These four factors were demonstrated to be all significantly crucial in supercritical carbon dioxide extraction operation, so as the two-variable interactions. The extracts of Aloe vera rind by supercritical carbon dioxide extraction and solvent extracts provided significantly higher free radical scavenging activity of 33.47% and 39.72% respectively compared to extracts of A oe vera gel extracted by ethanol with free radical scavenging activity of 14.15%. The inhibition percentage of extracts of Aloe vera and reference antioxidants followed the decreasing order: Trolox (76.77%) > ethanol extracts of Aloe vera skin (39.72%) > BHT (35.87%) > the extract of supercritical carbon dioxide extraction (33.47%) >a-tocopherol (25.62%) > ethanol extracts of Aloe vera pulp (14.15%). Compared to BHT and a-tocopherol, the extracts of Aloe vera skin by supercritical carbon dioxide extraction and ethanol showed stronger antioxidant activities. The components in rind of Aloe vera are responsible for higher antioxidant activity of Aloe vera extracts.Immunomodulatory activity of aloe polysaccharides was evaluated in mice. Mice were treated with tree dose of polysaccharides(2.5mg mL-1 -, 1.25mg mL"'and 0.625mg mL-1with 0.4ml/20g BW) for 30 day. Body weight, relative organ weight, delayed type of hypersensitivity (DTH) response, haemmaglutination titre(HT) and phagocytosis were studied in various groups of animals. At dose of 2.5 mg mL-1, a significant increase (P<0.05) in the DTH response and antibody titre in mice were observed while only a obviously increase in antibody titre at a dose of 1.25 mg mL-1. Overall, aloe polysaccharides showed a regulation effects on immune functions in mice at a dose dependent level. Further, somechemical characterization of aloe polysaccharides showed that these polysaccharides were rich in uronic acids with a composition similar to that of several antitumoral polymers found in different plant tissues. |
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