Submitted to: Journal of Agricultural Chemistry and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2013
Publication Date: 11/1/2013
Citation: Meepagala, K.M., Schrader, K., Burandt, C. 2013. Antibacterial compounds from Rutaceae with activities against Flavobacterium columnare and Streptococcus iniae. Journal of Agricultural Chemistry and Environment. 2(4):90-100.
Interpretive Summary: The discovery of environmentally safe, cost effective antibacterial compounds would benefit aquaculturists due to the limitations or the absence of current management approaches available for controlling the common bacterial species responsible for columnaris disease and streptococcosis. Many members in the Rutaceae family are sources of natural products with biological activities. For the current study, a rapid bioassay was used to evaluate compounds isolated from various plant families and compounds isolated and identified by bioassay guided fractionation of crude ethyl acetate extract of Murraya koenigii ( curry plant) leaves. In addition, we investigated several amides isolated from Amyris texana and Piper nigrum (Black pepper), and some synthetic analogs for antibacterial activity. A compound isolated from Murraya koenigii has shown the highest antibacterial activity against columnaris disease and streptococcosis.
Technical Abstract: Bioassay-guided fractionation of the ethyl acetate extract of Murraya koenegii (Rutaceae) leaves yielded isomahanine (1) and mahanine (2) with antibacterial activity towards bacteria species that cause columnaris disease and streptococcosis, common diseases in pond-raised channel catfish (Ictalurus punctatus) and other fresh water fish, respectively. The Gram-negative, rod-shaped bacterium Flavobacterium columnare is the cause of columnaris disease. The most common bacterial species responsible for streptococcosis in tilapia is Streptococcus iniae which is a Gram-positive, spherical-shaped cell. Isomahanine was found to have the strongest activity against F. columnare (isolate ALM-00-173) and S. iniae (isolate LA94-426) based on 24-h 50% inhibition concentration (IC50) and minimum inhibition concentration (MIC). The relative-to-drug-control (RDC) values for isomahanine were also among the lowest, especially the 24-h IC50 RDC values which were the lowest of any of the test compounds. Although compound (7), a nicotinamide isolated from Amyris texana (Rutaceae), had the lowest MIC (2.8±0 mg/L) of any of the test compounds against F. columnare ALM-00-173, the 24-h IC50 of 14.8±0.6 mg/L was higher than that of isomahanine and subsequently the 24-h IC50 RDC values for (E)-N-(2,4-dimethoxystyryl)nicotinamidewere almost a magnitude of order higher than those obtained for isomahanine. The cis isomer of (E)-N-(2,4-dimethoxystyryl)nicotinamide and compound (E)-7-(benzo(1,3)dioxol-5-yl)hept-6-en-1-ol had moderate toxicities against F. columnare ALM-00-173 based on MIC results. Isomahanine also had the strongest activity against S. iniae, with a 24-h IC50 of 1.3±0.1 mg/L and MIC of 3.5±0 mg/L, respectively.