This study aimed to optimize the extraction process of total polyphenols from Iris halophila Pall roots and evaluate their in vitro inhibitory effects on Fusobacterium nucleatum (Fn).The total polyphenols content in the roots of I.halophila was used as the evaluation index to investigate the effects of liquid-material ratio,extraction time and extraction times;Based on the results of single factor experiments,Box-Behnken response surface methodology was used to optimize the extraction process of total polyphenols from I.halophila roots.The inhibitory effects and growth process of total polyphenols with different mass concentrations on Fn were determined by agar perforation method and microdilution method.Meanwhile the effect on Fn biofilm formation was determined by crystal violet staining method.The results showed that the optimum extraction process of total polyphenols from I.halophila roots was as follows:liquid-material ratio was 20∶1 (mL/g),extraction times was 3,extraction time was 85 min.The yield of total polyphenols from I.halophila roots under these conditions was 36.52 mg/g.The optimal growth period of Fn was 40 h;The minimum inhibitory concentration of total polyphenols from I.halophila roots against Fn was 50 mg/mL,and the minimum bactericidal concentration was 200 mg/mL;When the drug concentrations were 12.5,25,50 and 100 mg/mL,the biofilm activity of Fn was 59.64%,47.80%,18.58%,and 4.78% respectively.The biofilm activity of Fn was negatively correlated with the concentration of total polyphenols from I.halophila roots (P<0.001).The optimized extraction process is stable and feasible,and the high content of total polyphenols show effective activity in inhibiting Fn and its biofilm,which lays a solid foundation for the rational development and utilization of I.halophila roots.

"> Box-Behnken response surface methodology, Iris halophila Pall roots, Fusobacterium nucleatum, total polyphenols, antibacterial activity