Antibacterial Activity of Norbelladine Analogue Alkaloids

HUGO CENTORBI; OLGA ALIENDRO; XIOMARA GAMBLUCH; ALEJANDRO ORDEN; FLORENCIA CARMONA VIGLIANCO; CLAUDIA MATTANA; SARA SATORRES

San Juan

Congreso; XLI Reunión Anual de la Sociedad de Biología de Cuyo; 2023

Sociedad de Biología de Cuyo

The Amaryllidaceae family of plants has attracted considerableattention due to the varied biological activities that exhibits its alkaloidconstituents, and its effects on human health have been widelyevaluated. However, there is a limited number of studies on thebioactivity of its precursors. The proto- alkaloid 4'-O-methylnorbelladinis a precursor of all Amaryllidaceaealkaloids such as haemanthamine, lycorine and galantamine. Theobjective of this work was to evaluate the antibacterial effect of two 4'-O-methylnorbelladin unnaturalanalogues, against strains of methicillin-resistant Staphylococcus aureus ATCC 43300, Listeria monocytogenes CLIP 74904 and Pseudomonas aeruginosa ATCC 27853. Compounds N-(p-hidroxifeniletil)-N-(p-flúor)bencilamina (1) and N-(p-hidroxifeniletil)-N-(p-hidroxi)bencilamina (2), obtained by condensation reaction between commercial aldehydes 4-fluorobenzaldehydeor 4-hydroxybenzaldehyde and tyramine. The minimal inhibitory concentration(MIC) and minimal bactericidal concentration (MBC) were determined by themicro-well dilution assay method, in trypticase soy broth (TSB) with addition0.01% (W/V) of 2,3,5-triphenyltetrazolium chloride as visual indicator ofbacterial growth. Suspensions of 106 UFC/mL for each strain wereused. Compounds 1 and 2 was dissolved in water and then serial twofolddilutions were made in concentration ranges from (μg/mL): 5000 to 2.44. The96-well plates were prepared by dispensing into each well 100 μL of TSB withindicator, 100 µL of serial dilutions of compounds and 5 μL of the inoculum. Inaddition, controls of TSB, strains and compound were also included. The plateswere incubated at 37°C for 24 h. under static conditions. The MIC was definedas the lowest concentration of the compounds, in which there was no visiblegrowth after incubation (no red colour). The MBC was determined by subculturingon trypticase soy agar (TSA), from the last three wells that showed no visible bacterialgrowth.  The experiments were performedin duplicate and then replicated at least twice. The MIC and CBM values for the microorganisms evaluated againstcompounds 1 and 2 were respectively (μg/mL): S. aureus1250/2500, 2500/5000; L.monocytogenes 625/1250, 1250/1250 and against P. aeruginosa, no antimicrobial activity was detected (CIM-CBM >5000 μg/mL for both compounds).  In this work, we observed that norbelladinanalogues tested were more active on gram positive bacteria compared to Pseudomonas aeruginosa. However, S. aureus was less affected than L. monocytogenes. Probably the non-activity againstP aeruginosa is due to factorsassociated with the outer membrane structure. The antibacterial activity of newsynthetic products has shown increasing interest in recent years for thetreatment of infections caused by pathogenic bacteria resistant to multipledrugs. However, additional studies are needed regarding the toxicity and appropriateroutes of administration of such products.