In earlier studies, flavone and wogonin were shown to have strong activity against the fish bacterial species Flavobacterium columnare which causes columnaris disease in channel catfish (Ictalurus punctatus). Flavone and wogonin analogs were therefore synthesized, with the objective of improving the efficacy of these flavones. The analogs were evaluated, along with thirteen other flavonoids from natural sources, for antibacterial activity against two isolates of F. columnare (ALM-00-173 and BioMed). The flavonoids chrysin (1a  ), 5,7-dihydroxy-4'-methoxy-flavone (11  ), isorhamnetin (26  ), luteolin (27  ), and biochanin A (29  ) showed strong antibacterial activity against F. columnare ALM-00-173 based on minimum inhibition concentration (MIC) results. Flavonoids 1a  , 8   (2-(4-methoxyphenyl)-5,6,7-trimethoxy-4H-chromen-4-one), 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 (IC50) results revealed that 27  and 29  were the most active against F. columnare ALM-00-173 (IC50 of 7.5 and 8.5 mg/L, respectively) while 26  and 29  were the most toxic against F. columnare BioMed (IC50 of 9.2 and 3.5 mg/L, respectively). These IC50 results were lower than the IC50 values for wogonin. 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). We nonetheless obtained valuable information on the antimicrobial activity of the synthetic and natural flavonoids against isolates of F. columnare, being reported here for the first time.

Synthesis of flavone analogs and activity against the fish bacterial species <i>Flavobacterium columnare</i>

248th National Meeting (2014)

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Synthesis of flavone analogs and activity against the fish bacterial species Flavobacterium columnare