Evaluation for inhibitory effects of natural flavonoids on neuraminidases

Objective: To investigate the inhibitory effects of 15 different natural flavonoids on neuraminidases(NAs) from influenza virus,and to evaluate the specificity of their inhibitory effects on NAs and analyze the structure-activity relationship(SAR).Methods: Fluorometric assay was used to test the activities of NAs in vitro.Results: All the 15 flavonoids possessed inhibitory activities against influenza virus NAs.Apigenin,luteolin,apiin,galuteolin,dinatin,scutellarin and kaempferol were the best;their IC50 values were lower than 60μmol·L-1.The effects of apigenin,luteolin,apiin,galuteolin,scutellarin and kaempferol on influenza virus NAs were much more potent than their effects on NAs from vibrio cholerae and rat liver,while dinatin had similar effects on these NAs.Conclusion: All the 15 flavonoids inhibit influenza virus NAs,and effects of apigenin,luteolin,apiin,galuteolin,dinatin,scutellarin and kaempferol are the most potent.The SAR analysis of flavonoids' effects on influenza virus NAs reveals that for inhibitory potency,C4=O and C2=C3 functionalities are essential,and the 5-OH,7-OH and 4'-OH are important.Apigenin,luteolin,apiin,galuteolin,scutellarin and kaempferol have shown the specificity of inhibitory effects on influenza virus NAs.These findings provide important information for the exploitation and utilization of these flavonoids.