Study On The Bioactivity Of Polysaccharides Obtained From Dendrobium Denneanum Kerr.

With the development of economics,people pay more attention tophysical and spiritual needs.For modern landscape,people are no longer only satisfied with their recreational and ornamental functions.The health care garden gradually fits the needs of people’s growth,which has also promoted the rise of"horticultural therapy"."Horticultural therapy"provides a new idea for landscape architecture design,and garden plants are the main body of"horticultural therapy".The secondary metabolites in plants are the material basis of"horticultural therapy".Garden plants with medicinal value have become the first choice of"horticultural therapy",and the ornamental medicinal plants will be more applied to the design of garden landscape.The garden plants only have a single ornamental application.The study of the medicinal value of garden plants can make it more valuable in the application of garden landscape,make the resources more fully utilized,and provide ideas for the construction of functional landscape.Dendrobium denneanum Kerr.is a kind of ornamental plants and belongs to orchids.In order to investigate the structure characteristics,antioxidant activities and immunemodulatory activity of polysaccharides of Dendrobium denneanum Kerr.,six samples（ddp1-1,ddp1-2,ddp1-3,ddp40,ddp60 and ddp80）were obtained from the dried stem.Water extraction,Alkali extraction method and Stepwise ethanol precipitation method were used.The result of the Mw of six sample was:ddp1-3（2.45×10⁵ Da）>ddp40（1.70×10⁵ Da）>ddp1-2（8.80×10⁴）>ddp60（5.78×10⁴ Da）>ddp80（1.36×10⁴ Da）>ddp1-1（6.87×10³Da）.And the Fourier-transform infrared spectroscopy of six samples revealed typical characteristics of polysaccharides.The six sample types had different contents.This was proved by their different adsorption peak intensities.According the result of FTIR,five samples（ddp1-1,ddp1-3,ddp40,ddp60 and ddp80）were found that they have a pyranose form of saccharides.However,ddp1-2 has a Furan form of saccharides.Three samples（ddp1-1,ddp40 and ddp60）had alpha configuration and two samples（ddp1-2,ddp1-3）had beta configuration.The free radicals（ABTS⁺,DPPH⁺,OH^-）and reducing power were used to determine the antioxidant activity of ddps.The result showed that the activities of ddps increased in a concentration dependent manner.The ddp80 was found had the best antioxidant activity.In the reducing power test,the IC₅₀ value of ddp80 was 11.566mg/mL.Based on the quantification of ABTS radical scavenging,the IC₅₀ value of ddp80 was 23.59 mg/mL and the the radical scavenging activity got to 88.23%when the concentration of ddp80 got to80mg/mL.The IC₅₀ values of ddp80（23.754 mg/ml）showed significant DPPH radical scavenging activity and the the radical scavenging activity got to 100%when the concentration of ddp80 got to 160mg/mL.The the radical scavenging activity to hydroxyl radical got to 139.55U/mL when the concentration of ddp80 got to 320mg/mL.To study on the effects of ddps to immunological activity of murine peritoneal macrophages,the changes in contents of cytokines were analyzed.The result showed that ddp80 could promot the production of TNF-αsignificantly when the concentration was at200mg/mL.Besides,ddp1-2,ddp1-3 and ddp40 could could promot the production of IL-1β.However,ddp1-3 and ddp40 had a better perfoimance than ddp1-2.As for IL-6,ddp1-2 and ddp 80 could promot its production.These evidence proved that 6 ddps exhibited moderate biological activities.And ddp80had the best peromance and the protein of immunemodulatory activity.