Extracts of Edible and Medicinal Plants Damage Membranes of Vibrio cholerae

Abstract

The use of natural compounds from plants can provide an alternative approach against food-borne pathogens. The mechanisms of action of most plant extracts with antimicrobial activity have been poorly studied. In this work, changes in membrane integrity, membrane potential, internal pH (pH in ), and ATP synthesis were measured in Vibrio cholerae cells after exposure to extracts of edible and medicinal plants. A preliminary screen of methanolic, ethanolic, and aqueous extracts of medicinal and edible plants was performed. Minimal bactericidal concentrations (MBCs) were measured for extracts showing high antimicrobial activity. Our results indicate that methanolic extracts of basil (Ocimum basilicum L.), nopal cactus (Opuntia ficus-indica var. Villanueva L.), sweet acacia (Acacia farnesiana L.), and white sagebrush (Artemisia ludoviciana Nutt.) are the most active against V. cholera, with MBCs ranging from 0.5 to 3.0 mg/ml. Using four fluorogenic techniques, we studied the membrane integrity of V. cholerae cells after exposure to these four extracts. Extracts from these plants were able to disrupt the cell membranes of V. cholerae cells, causing increased membrane permeability, a clear decrease in cytoplasmic pH, cell membrane hyperpolarization, and a decrease in cellular ATP concentration in all strains tested. These four plant extracts could be studied as future alternatives to control V. cholerae contamination in foods and the diseases associated with this microorganism.

Isolation, characterization and mode of antimicrobial action againstVibrio choleraeof methyl gallate isolated fromAcacia farnesiana

“…As expected, the MBC of the isolated methyl gallate was much less than the previously reported MBC of A. farnesiana whole extract (500 and 900 lg ml À1 , Sanchez et al (2010); against 30 and 50 lg ml À1 for strains 1837 and 569-B, respectively). The antimicrobial mode of action of methyl gallate was determined by the evaluation of several parameters in V. cholerae cells, such as cytoplasmic pH, membrane potential and proton motive force, which are indicators of cellular homeostasis; all these parameters help determine the functionality of the bacterial cell membrane (Lambert et al 2001;Ultee et al 2002).…”

“…The effect of the isolated compound on pH in was determined according to the method reported by Breeuwer et al (1996) and modified by Sanchez et al (2010). Briefly, LB broth (5 ml) was inoculated (1%) with overnight-activated cultures of Vibrio strains and incubated at 37°C for 3 h. Cells were centrifuged (1500 g, 10 min) and washed twice with 50 mmol l À1 HEPES buffer containing 5 mmol l À1 EDTA, pH 8.…”

“…The antimicrobial effect of plant extracts against V. cholerae has been previously reported (Garcıa et al 2006;Sanchez et al 2010). Plants such as Costus spiralis (ethanolic extract, resuspended in water; Perez et al 2008), Morinda morindo€ ıdes (ethanolic extract; Koffi et al 2011), Terminalia arjuna (ethanolic extract; Fakruddin et al 2011), Saraca indica, Datura stramonium (ethanolic extracts; Sharma and Patel 2009), Terminalia chebula (extracted in petroleum ether, CHCl 3 , dimethylformamide, EtOH and H 2 O) and Cassia auriculata (methanolic extract; Senthilkumar and Reetha 2011) have shown good vibriocidal activity.…”

“…(sweet acacia), also known as Vachellia farnesiana (L.) Wight & Arn, is widely distributed in Mexico and Central America, although the species has a pantropical distribution incorporating Northern Australia and Southern Asia (Parrotta 2001;Sanchez et al 2010). The plant has many uses in traditional medicine including to treat diarrhoea, dysentery, tuberculosis and as a treatment for indigestion (Parrotta 2001).…”

Cytotoxicity and effect of extraction methods on the chemical composition of essential oils of Moringa oleifera seeds

“…Essential oils are aromatic and volatile compounds found in most parts of plant materials such as the leaves, seed, flower, bark, fruit, and peel (Sánchez et al, 2010). The chemical compositions of essential oils are secondary metabolites, which play important roles in a plant's defense against microbial attacks and have been added to foods as spices for decades (Hyldgaard et al, 2012).…”