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Activities of Wogonin Analogs and Other Flavones against Flavobacterium columnare

Cheng-Xia Tan, Kevin K. Schrader, Ikhlas A. Khan, Agnes M. Rimando
Chemistry & biodiversity 2015 v.12 no.2 pp. 259-272
Flavobacterium columnare, Ictalurus punctatus, antibacterial properties, bioassays, biochanin A, chalcone, columnaris disease, disease control, inhibitory concentration 50, isorhamnetin, luteolin, minimum inhibitory concentration, synthesis, toxicity
In our continuing pursuit to discover natural products and natural product-based compounds to control the bacterial species Flavobacterium columnare which causes columnaris disease in channel catfish (Ictalurus punctatus), we synthesized flavone and chalcone analogs, and evaluated these compounds, along with flavonoids from natural sources, for antibacterial activities against two isolates of F. columnare (ALM-00-173 and BioMed) using a rapid bioassay. The flavonoids chrysin (1a), 5,7-dihydroxy-4'-methoxy-flavone (11), isorhamnetin (26), luteolin (27), and biochanin A (29), and chalcone derivative 8b showed strong antibacterial activity against F. columnare ALM-00-173 based on minimum inhibition concentration (MIC) results. Flavonoids 1a, 8, 11, 13 (5,4'-dihydroxy-7-methoxy-flavone), 26, and 29 had strong antibacterial activity against F. columnare BioMed based upon MIC results. The 24-h 50% inhibition concentration (IC(50)) results revealed that 27 and 29 were the most active against F. columnare ALM-00-173 (IC(50) of 7.5 and 8.5 mg/L, respectively) while 26 and 29 were the most toxic against F. columnare BioMed (IC(50) of 9.2 and 3.5 mg/L, respectively). These IC50 results were lower than the IC(50) values obtained for wogonin against F. columnare ALM-00-173 and F. columnare BioMed (28.4 and 5.4 mg/L, respectively). However, based on MIC results, none of the compounds evaluated in this study were as active as wogonin (MIC = 0.3 mg/L for each F. columnare isolate). Further modification of the wogonin structure to enhance antibacterial is of interest.