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Research Project: Management of Off-flavors and Undesirable Bacteria in Aquaculture

Location: Natural Products Utilization Research

Title: Activities of wogonin analogs and other flavones against Flavobacterium columnare

Author
item Tan, Cheng-xia - Zhejiang University
item Schrader, Kevin
item Khan, Ikhlas - University Of Mississippi
item Vacant, Vacant

Submitted to: Chemistry and Biodiversity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2014
Publication Date: 2/10/2015
Publication URL: http://handle.nal.usda.gov/10113/62340
Citation: Tan, C., Schrader, K., Khan, I.I., Rimando, A.M. 2015. Activities of wogonin analogs and other flavones against Flavobacterium columnare. Chemistry and Biodiversity. 12:259-272.

Interpretive Summary: Columnaris disease in channel catfish which is caused by the bacterial fish species Flavobacterium columnare, is one of the most common bacterial fish diseases, causing heavy economic losses to various aquaculture industries. As part of our studies to discover natural products and natural product-based compounds for the control of Flavobacterium columnare, we synthesized derivatives of wogonin and flavones, which were previously found to possess strong antibacterial activity towards two isolates of F. columnare, ALM-00-173 and BioMed. We synthesized eighteen flavone and three chalcone analogues and these compounds were evaluated, along with thirteen other flavonoids from natural sources, for antibacterial activity against the two of F. columnare isolates. Based on minimum inhibitory concentration (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 however report valuable information, being that these synthetic and natural flavonoids were tested for activity against isolates of F. columnare for the first time. Further modification of the wogonin structure to enhance antibacterial is a subject of interest.

Technical Abstract: In our continuing pursuit to discover natural products and natural product-based compounds for the control of the bacterial species Flavobacterium columnare which causes columnaris disease in channel catfish (Ictalurus punctatus), we synthesized eighteen flavone and three chalcone analogues and these compounds were evaluated, along with thirteen other flavonoids from natural sources, for antibacterial activity 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 (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 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.