Antimicrobial activity of eleagnine isolated from the seed cotyledons of Chrysophyllum albidum

This study evaluated the antimicrobial activity of eleagnine, a β-carboline alkaloid isolated from seed cotyledons of Chrysophyllum albidum G. Don Holl (Sapotaceae), and determined factors affecting it. Antimicrobial activities of eleagnine were determined using the agar diffusion and microdilution methods against selected typed organisms (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida spp.), clinical isolates (S. aureus, E. coli) and Trichophyton. The effects of inoculum size and pH on the bacteriostatic activity were studied using agar and broth dilution methods. Bactericidal/fungicidal activities were also evaluated using viable count technique. Cytotoxicity was determined using brine shrimp lethality test. Eleagnine showed higher bacteriostatic activity against Gram-positive organisms and Candida spp. than Gram-negative bacteria but showed no activity against Trichophyton. The MIC of eleagnine obtained by microdilution tests ranged from 9.77 μg/mL against S. aureus, 156.25 μg/mL for C. albicans to 312.5 μg/mL for E. coli and P. aeruginosa. Inoculum size (105-107 orgs/mL) did not appreciably affect activity but pH from 5.85 to 8.09 increased the activity against S. aureus and E. coli, suggesting the unionized form as the active compound. Eleagnine (100-400 μg/mL) produced a 4-5 log survivor reduction of S. aureus and E. coli in 30 min. LC50 of eleagnine was 18.8 mg/mL indicating minimal cytotoxicity. This study showed that eleagnine is bactericidal with low cytotoxicity. Factors affecting its activity (pH, solvent) could be optimized in developing effective antimicrobial products alone or in combination with other agents.Keywords: Eleagnine, Chrysophyllum albidum, antimicrobial, inoculum size, p

Atividade antimicrobiana de óleos essenciais em bactérias patogênicas de origem alimentar Antimicrobial activity of essential oils against sessile and planktonic pathogens of food source

Objetivou-se identificar e quantificar os constituintes e avaliar a atividade antimicrobiana dos óleos essenciais de Mentha piperita, Cymbopogon citratus, Ocimum basilicum e Origanum majorana contra cepas de Escherichia coli enteropatogênica, Salmonella enterica Enteritidis, Listeria monocytogenes e Enterobacter sakazaki. A obtenção dos óleos essenciais foi realizada a partir de folhas secas, empregando-se a técnica de hidrodestilação e utilizando-se a aparelho de Clevenger modificado. A atividade antibacteriana dos óleos essenciais foi determinada pelo método de difusão em ágar. Observou-se que os óleos essenciais inibiram o crescimento bacteriano, mas a efetividade foi variada. Entre os óleos essenciais testados, M. piperita apresentou maior atividade antibacteriana para E. coli, (8.106 UA mL-1) quando comparada as demais bactérias, atividade moderada para Salmonella enterica Enteritidis e Enterobacter sakazakii (1.706 e 3.200 UA mL-1 respectivamente) e baixa atividade para Listeria monocytogenes (106,67 UA mL-1). Já óleo essencial de Cymbopogon citratus apresentou maior atividade antimicrobiana frente a E. coli (9.386 UA mL-1) e atividade moderada frente a Enterobacter sakazakii, Salmonella enterica Enteritidis e Listeria monocytogenes (2.773 UA mL-1 para ambas). Ocimum basilicum apresentou maior atividade antibacteriana frente E. coli e Enterobacter sakazakii (6.826 e 8.106 UA mL-1 respectivamente), moderada atividade frente a Salmonella enterica Enteritidis (1.600 UA mL-1) e não apresentou atividade frente a Listeria monocytogenes.Origanum majorana também foi testado neste estudo e apresentou maior atividade antimicrobiana frente E. coli (5.973 UA mL-1), atividade moderada para Salmonella enterica Enteritidis e Enterobacter sakazakii (1.706 e 2.346 UA mL-1 , respectivamente) e não apresentou atividade para Listeria monocytogenes.<br>ABSTRACT The objective of this work was to identify and quantify the constituents, and to evaluate the antimicrobial activity of the essential oils from Mentha piperita, Cymbopogon citratus, Ocimum basilicum and Origanum majorana, against enteropathogenic Escherichia coli, Salmonella enterica Enteritidis, Listeria monocytogenes and Enterobacter sakazakii. The essential oils were obtained from dried leaves by using the hydrodistillation technique and the modified Clevenger apparatus, and their bacterial activity was determined by using the agar diffusion technique. The essential oils inhibited bacterial growth, but their effectiveness was varied. Among the essential oils tested, that from M. piperita showed a greater antimicrobial activity against E. coli (8.106 UA mL-1), moderate activity for S. enterica Enteritidis and E. sakazakii (1.706 e 3.200 UA mL-1 respectively) and low activity for L. monocytogenes (106,67 UA mL-1). However, the essential oil from C. citratus presented a greater antimicrobial activity against E. coli (9.386 UA mL-1) and a moderate activity against E. sakazakii, S. enterica Enteritidis and L. monocytogenes (2.773 UA mL-1 for both). The essential oil from O. basilicum showed a greater antimicrobial activity against E. coli and E. sakazakii (6.826 e 8.106 UA mL-1 respectively),moderate activity against S. enterica Enteritidis (1.600 UA mL-1), and was inactive against L, monocytogenes. Origanum majorana, which was also tested in our work, showed a greater antibacterial activity against E. coli, (5.973 UA mL-1) moderate activity against S. enterica Enteritidis and E. sakazakii (1.706 e 2.346 UA mL-1 , respectively), and was inactive against L. monocytogenes