Location: Natural Products Utilization ResearchTitle: Ungeremine and its hemisynthetic analogues as bactericides against Flavobacterium columnare Author
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2013
Publication Date: 1/20/2013
Citation: Schrader, K., Avolio, F., Andolfi, A., Cimmino, A., Evidente, A. 2013. Ungeremine and its hemisynthetic analogues as bactericides against Flavobacterium columnare. Journal of Agricultural and Food Chemistry. 61:1179-1183. Interpretive Summary: Several analogs of ungeremine, an antibacterial compound found in some plants, were synthesized and evaluated in the laboratory for activity against a type of bacteria that causes disease in pond-raised channel catfish. One of the analog compounds was found to have similar activity compared to ungeremine
Technical Abstract: The Gram-negative bacterium Flavobacterium columunare is the cause of colmunaris disease in channel catfish (Ictalurus punctatus). In a previous study, the betaine-type alkaloid ungeremine, 1 obtained from Pancratium maritimum L. was found to have strong antibacterial activity against F. columnare. In this study, analogues of 1 were evaluated using a rapid bioassay for activity against F. columnare to determine if the analogues might provide greater antibacterial activity and in order to determine structure-activity relationship of the test compounds. Several ungeremine analogues were prepared by hydrochlorination of the alkaloid and by selenium dioxide oxidation of both lycorine, 7 and pseudolycorine, 8 which yielded the isomer of ungeremine, 3 and zefbetaine, 4, respectively. The treatment of lycorine with phosphorus oxychloride allowed the synthesis of an anhydrolycorine lactam, 5 showing, in respect to 1, the deoxygenation and oxygenation of C-2 and C-7 of C and B rings, respectively. The results of the structure-activity relationship studies showed that the aromatization of the C ring and the oxidation to an azomethine group of C-7 of the B ring are structural features important for antibacterial activity. In addition, the position of the oxygenation of the C ring as well as the presence of the 1,3-dioxole ring joined to the A ring of the pyrrolo[de]phenthantridine skeleton also plays a significant role in imparting antibacterial activity. Based on 24-h 50% inhibition concentration (IC50) results, ungeremine hydrochloride, 2 was similar in toxicity to 1 while 5 had the lowest activity.