Rapid identification of isoprenylated flavonoids constituents with inhibitory activity on bacterial neuraminidase from root barks of paper mulberry (Broussonetia papyrifera)

This study was to assess the possibility of using competitive and slow binding experiments with affinity-based ultrafiltration UPLC-QTof-MS analysis to identify potent bacterial neuraminidase (bNA) inhibitors from the Broussonetia papyrifera roots extract. To isolate unbound compounds from the enzyme-binding complex, the root bark extracts were either incubated in the absence of bNA, in the presence of bNA, or with the time-dependent bNA before the ultrafiltration was performed. Thirteen flavonoids were separated from the target extract, and their inhibitory activities were tested against bNA. The isolated flavonoids exhibited potent inhibition against NA (IC50 =0.7-54.0 mu M). Our kinetic analysis of representative active flavonoids (1, 2, and 6) showed slow and time-dependent reversible inhibition. Additionally, chalcones exhibited noncompetitive inhibition characteristics, whereas flavonols and flavans showed mixed-type behavior. The computational results supported the experimental behaviors of flavonoids 2, 6,10, and 12, indicating that bounded to the active site, but flavonoids 6 and 10 binds near but not accurately at the active site. Although this is mixed-type inhibition, their binding can be considered competitive. (C) 2021 Published by Elsevier B.V.

Automated summary

This study used competitive and slow binding experiments with affinity-based ultrafiltration UPLC-QTof-MS analysis to identify potent bacterial neuraminidase inhibitors from Broussonetia papyrifera roots extract. Thirteen flavonoids were isolated and tested for inhibitory activities against bNA, showing slow and time-dependent reversible inhibition for some compounds, noncompetitive inhibition characteristics for chalcones, and mixed-type behavior for flavonols and flavans. Computational results supported experimental behaviors of certain flavonoids, indicating competitive binding despite mixed-type inhibition.