No abstract

A series of novel flavones derivatives were synthesized based on modification of the active ingredients of a traditional Chinese medicine Scutellaria baicalensis GEORGI and screened for anti-influenza activity. The synthetic baicalein (flavone) analogs, especially with the B-rings substituted with bromine atoms, were much more potent than oseltamivir or ribavirin against H1N1 Tamiflu-resistant (H1N1 TR) virus and usually with more favorable selectivity. The most promising were 5b, 5c, 6b and 6c, all displaying an 50% effective concentration (EC 50 ) at around 4.0-4.5 µM, and a selective index (SI 50% cytotoxic concentration (CC 50 )/ EC 50 )>70. For seasonal H3N2-infected influenza virus, both 5a and 5b with SI >17.3 indicated superior to ribavirin. The flavonoids having both not-naturally-occurring bromo-substituted B-rings and appropriate hydroxyls positioning on the A-rings might be critical in determining the activity and selectivity against H1N1-Tamiflu-resistant infected influenza viruses.

A series of novel isoflavonoids were synthesized based on structural modifications of daidzein, an active ingredient of traditional Chinese medicine (TCM) and evaluated for their anti-influenza activity, in vitro, against H1N1 Tamiflu-resistant (H1N1 TR) virus in the MDCK cell line. Among them, 4-oxo-4H-1-benzopyran-8-carbaldehydes 11a-11g were most promising, and they demonstrated better activities and selectivities comparable to those the reference ribarivin, a nucleoside antiviral agent. 3-(4-Bromophenyl)-7-hydroxy-4-oxo-4H-1-benzopyran-8-carboxaldehyde (11c) displayed the best inhibitory activity (EC50 , 29.0 μM) and selectivity index (SI>10.3). Analysis of the structureactivity relationships (SAR) indicated that both the non-naturally-occurring Br-substituted B-ring and appropriate CHO and OH groups on the A-ring might be critical for the activity and selectivity against H1N1 TR influenza viruses.