Abstract: The antimicrobial activity and extraction conditions of Nitellopsis obtusa was studied. The results showed that the ethanol extracts had obvious antimicrobial activities to Staphylococcus aurous, Bacillus subtilis and indistinctive activities to Proteus vulgaris, Escherichia coli, Saccharomyces cerevisiae and Aspergillus flavus. Single factor test of extraction conditions of N.obtusa was also carried of by measuring the size of anti-microbe circle diameter. Through orthogonal design and experiments, it indicated that antibacterial activity was significantly influenced by the material to solvent ratio and extraction temperature of the extracts of N.obtusa, especially to S.aurous and B.subtilis. The optimum extraction conditions of N.obtusa were obtained the material to solvent ratio 1∶20, extraction temperature 85℃, 50% ethanol solution and 6 hours extraction time.

Key words: Nitellopsis obtusa, antimicrobial activity, optimization of extraction conditions