Abstract: Objective: To investigate the extraction and antioxidant activity of total flavonoids from whole plants of Saxifraga tangutica Engl. Methods: Orthogonal array design was employed to optimize extraction conditions. The antibacterial effect of total flavonoid extract at different concentrations on 6 strains was evaluated by agar diffusion and broth dilution methods. Results: According to the results of analysis of variance, four extraction parameters could be ranked in decreasing order of their effect on extraction efficiency as follows: extraction number ＞ ethanol concentration ＞ ultrasonic treatment time ＞ material-to-liquid ratio. The optimal extraction conditions were ethanol concentration of 80%, material-to-liquid ratio of 1:25 (g:mL), ultrasonic treatment time of 35 min, repeated ultrasonic treatment number of 4, ultrasonic power of 100 W and extraction temperature of 50 ℃. Under these conditions, the extraction efficiency of total flavonoids was 81.73 mg/g. Total flavonoids from whole plants of Saxifraga tangutica Engl. had inhibitory effect on all tested strains. The minimum inhibitory concentrations were 0.156, 0.313 mg/mL and 0.625 mg/mL against Staphyloccus aureus, Bacillus subtilis and Escherichia coli, respectively. The anti-yeast activity was weak. No inhibitory effect on mold was found. Conclusion: This study can provide experimental references for further development and utilization of Saxifraga tangutica Engl.

Key words: Saxifraga tangutica Engl., total flavonoids, ultrasonic treatment, extraction process, antibacterial activity