Abstract: In order to study the application value of Dendrobium nobile,we investigated the particle structure and antioxidant activities of ultramicro powder and common powder of Dendrobium nobile.It was found that the ultrastructure of Dendrobium nobile was changed by ultramicro pulverization,and the cell wall net-like structure and fiber components were destroyed.The particle size was small and its distribution was more concentrated.Furthermore,the reduce power,and scavenging abilities of DPPH·,OH· and O₂^–· were studied.The reduce power,and scavenging abilities of DPPH·,OH· and O₂^–· has been increased by 1.6,1.4,1.5,1.5 times,respectively,compared to those extracted solution (The concentration of extracted solution:60 mg/mL).Ultramicro pulverization has changed the physical-chemical properties of Dendrobium nobile,destroyed its original structure,improved its antioxidant capacities,and had a certain potential in the application of medicine and food industries.

Key words: Dendrobium nobile, submicron powder, common powder, structure, SEM, antioxidant activity