Preparation of Nostoc flagelliforme cell having antioxidation activity and Nostoc flagelliforme extract

The invention relates to a black moss cell with antioxidant activity and a preparation method of a black moss extract. The preparation method is used for obtaining black moss cell powder, exocellular polysaccharide and cell extracting solution which can effectively eliminate superoxide anion radicals and hydroxyl radicals. The preparation method comprises the following steps: autotrophic and mix-cultured black moss cells are ground to obtain the cell powder, autotrophic and mix-cultured black moss exocellular polysaccharide is extracted from autotrophic and mix-cultured black moss cell culture solution, the cell powder is added with phosphate buffer solution, freeze thawing is carried out for five times and the mixture solution is centrifuged to extract supernatant so as to obtain the cell extracting solution. The black moss cell powder, the exocellular polysaccharide and the cell extracting solution have the activity of eliminating the superoxide anion radicals, the cell extracting solution has the activity of eliminating the hydroxyl radicals, and the black moss cell and the black moss extract are potential natural antioxidants and functional food.