Phenolic compounds, antioxidant and antibacterial activities of three Ericaceae from Algeria

International audienceHerbs of the Ericaceae family are commonly found in Algeria and used in traditional medicine as antiseptic, diuretic, astringent, depurative, and to treat scalds and wounds. The methanolic extracts of three species, Arbutus unedo L. (A. unedo, leaves), Erica arborea L. (E. arborea, flowered aerial parts), and Erica multiflora L. (E. multiflora, flowered aerial parts), were compared regarding their content in phenolic compounds, their antioxidant, and antibacterial activities. A. unedo harbors the highest content in total phenolics and flavonoids, followed by E. arboreaE. multiflora. The contents in total phenolics and flavonoids showed a correlation with the measured antioxidant (hydrogen-donating) activities; this was particularly the case for flavonoids content. The A. unedo extract showed antibacterial activity against all the tested strains (Staphylococcus aureus ATCC 6538, S. aureus C100459, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 9027); however, the E. arborea and E. multiflora extracts showed antibacterial activity only against Gram positive bacteria. Some polyphenols were identified in the three herbs by thin-layer chromatography and high-performance liquid chromatography coupled with diode array and mass spectrometry detection; from these, caffeic acid, p-coumaric acid, naringin, quercetin and kaempferol are reported for the first time in E. multiflora

Phytochemical study, direct and indirect antimicrobial activity of Cordia gilletii De Wild, Boraginaceae

Les maladies infectieuses constituent un sérieux problème de santé publique aussi bien dans les pays en développement où elles sont la principale cause de taux de mortalité élevés, que dans les pays industrialisés où les résistances aux antibiotiques existants se développent de façon alarmante. Cette situation engendre un besoin sans cesse croissant de trouver de nouveaux composés antimicrobiens et/ou inhibiteurs de mécanismes de résistances aux antibiotiques. Les plantes médicinales, notamment celles utilisées de façon traditionnelle dans les pays en développement, constituent une source potentielle de ce type de composés. C’est dans ce cadre que l’espèce Cordia gilletii De Wild (Boraginaceae), une plante dont les écorces de racines et les feuilles sont traditionnellement utilisées en République Démocratique du Congo pour combattre les maladies infectieuses, a été étudiée sur le plan tant de ses activités biologiques que de sa composition chimique. Les extraits obtenus à partir des écorces de racines de cette plante ont montré d’intéressantes activités biologiques, (i) un effet antimicrobien direct (bactéricide pour les bactéries gram positif et bactériostatique pour les gram négatif) et indirect (augmentation ou restauration de l’activité des antibiotiques vis-à-vis des souches résistantes); (ii) un effet inhibiteur sur deux des gènes impliqués dans le quorum sensing de Pseudomonas aeruginosa, lasB and rhlA; (iii) un effet antiplasmodial sur une souche chloroquino-sensible de Plasmodium falciparum; (iv) un effet antioxydant mis en évidence par réaction avec le radical libre DPPH. Pour les extraits de feuilles, seule l’activité antiplasmodiale a été observée. Les extraits d’écorces de racines, doués d’activité antimicrobienne directe (extrait méthanolique) et indirecte (extrait n-hexanique) ont été soumis à une série de fractionnements dans le but d’isoler et d’identifier les composés actifs. Pour suivre l’activité lors des fractionnements, le milieu de culture utilisé pour la détection des composés actifs sur une plaque chromatographique (CCM-bioautographie) a été optimisé. Le composé férulaldéhyde, isolé de l’extrait méthanolique, a montré des propriétés antimicrobiennes, antioxydantes et antiplasmodiales. De l’extrait n-hexanique ont été isolés deux composés, l’un actif, le lupéol et l’autre inactif, la friedéline. Le lupéol a montré un effet antimicrobien indirect en réduisant la CMI de certains antibiotiques vis-à-vis d’une souche de MRSA. Ces trois composés, s’ils ont déjà été identifiés dans d’autres plantes, sont décrits pour la première fois dans l’espèce Cordia gilletii ;et ce travail constitue le premier rapport de l’effet antimicrobien indirect du lupéol. Dans le but de s’assurer de l’innocuité des extraits de C. gilletii, une recherche d’alcaloïdes pyrrolizidiniques (APs) a été réalisée par GC-MS. Ces alcaloïdes présentent en effet un réel danger pour la santé humaine et la famille des Boraginaceae, à laquelle appartient l’espèce C. gilletii, est connue comme une des principales sources de ces composés. Aucun AP n’a pu être mis en évidence dans les extraits d’écorces de racines et de feuilles de cette plante jusqu’à une limite de détection de 2 ppm, suggérant ainsi une absence de risque toxicologique en relation avec ces alcaloïdes. Ces résultats rassurants restent à confirmer sur d'autres échantillons obtenus dans des lieux de récolte différents.Le présent travail montre que C. gilletii peut agir contre les microorganismes pathogènes par :(i) son action antimicrobienne directe (due entre autre au férulaldéhyde); (ii) son effet antimicrobien indirect (dû au lupéol), effet permettant d’augmenter ou de restaurer l’activité des antibiotiques vis-à-vis des souches résistantes ;et (iii) son effet inhibiteur de l’expression des gènes du quorum sensing, effet permettant d’atténuer la virulence d’agents infectieux. Ces actions peuvent permettent de faire face aux infections dues notamment à des microorganismes résistants.Infectious diseases remain a serious public health problem both in developing countries, where they are the main cause of the high mortality rates recorded, and in industrialized countries where there is an alarming incidence of antibiotic resistance. There is thus an increasing need for new compounds that can act by a direct antimicrobial effect or by an indirect effect, inhibiting resistance mechanisms of microorganisms. Medicinal plants, particularly those traditionally used against infectious diseases in developing countries, are a probable source for these types of compounds. In this context, Cordia gilletii De Wild (Boraginaceae), a medicinal plant from which root barks and leaves are traditionally used against infectious diseases in Democratic Republic of Congo, was investigated for biological activities and phytochemical composition. Root bark extracts showed interesting biological activities: (i) antimicrobial properties, acting directly (bactericid and bacteriostatic effects against gram positive and gram negative bacteria, respectively) or indirectly (enhancement or restoration of antibiotic activity on resistant strains); (ii) inhibitory effect on the expression of two Pseudomonas aeruginosa QS genes, lasB and rhlA; (iii) antiplasmodial effect against a chloroquine sensitive strain of Plasmodium falciparum; (iv) antioxidant effect determined by the free radical DPPH quenching. Leaves extracts showed only antiplasmodial activity. Root barks extracts with the highest direct (methanol extract) and indirect (n-hexane extract) antimicrobial properties were fractionated to isolate and to identify the active compounds. To bio-guide the fractionation, the culture medium for the detection of active compounds on chromatographic plates (TLC-bioautography) was optimized. The compound ferulaldehyde, isolated from the methanol extract, showed antimicrobial, antioxidant and antiplasmodial properties. From the n-hexane extract two compounds were isolated, lupeol and friedelin. Lupeol showed indirect antimicrobial effect by decreasing the MIC of some antibiotics against MRSA; whereas friedelin was inactive. Although these three compounds have already been described in other plant species, this is the first report of their occurence in Cordia gilletii; the indirect antimicrobial effect of lupeol is described for the first time in this work. As it belongs to the family of Boraginaceae, a family well known as one of the most important sources of pyrrolizidine alkaloids (PAs), Cordia gilletii is susceptible to contain these toxic compounds that were consequently researched. A GC-MS analysis did not reveal the presence of PAs (detection limit, 2 ppm) in root barks and leaves extracts of C. gilletii, suggesting a lack of PA-related toxicity of this plant. This reassuring finding needs to be confirmed with samples harvested at different locations.This work reveals that C. gilletii may act against pathogenic microorganisms by: (i) a direct antimicrobial effect (partly due to férulaldéhyde); (ii) the enhancement or restoration of antibiotic activity against resistant strains (effect of lupeol); and (iii) an inhibitory effect on the expression of quorum sensing regulator genes, decreasing the virulence of microorganisms. These actions could help to fight infections caused by resistant strains. Doctorat en Sciences biomédicales et pharmaceutiquesinfo:eu-repo/semantics/nonPublishe

Medicinal Plants: A Tool to Overcome Antibiotic Resistance ?

Bacterial antibiotic resistance has become a serious problem of public health that concerns almost all antibacterial agents and that manifests in all fields of their application. Consequently, there is an increasing interest in the search for new compounds which can act by a direct antimicrobial effect or by inhibiting resistance mechanisms of microorganisms of medical importance. Medicinal plants nowadays remain a valuable source for this kind of compounds. The direct antimicrobial properties of a number of natural compounds have indeed been reported; such compounds act by many mechanisms, including: (i) complexation with macromolecules such as proteins and polysaccharides, thus inhibiting their functions (polyphenols); (ii) disruption of microbial membranes (lipophilic flavonoids, terpenoids, plant defensins); and (iii) inhibition of adhesion of microbial proteins to host polysaccharide receptors (polypeptides). Medicinal plants also provide compounds which are not necessarily effective against microorganisms, but which enhance or restore the activity of antibiotics by inhibiting resistance mechanisms. These compounds belong to several phytochemical groups and act as inhibitors of efflux pumps (flavonoids, terpenoids, alkaloids); inhibitors of PBP 2a (quinones, terpenoids), enhancers of the permeability of bacterial membrane (terpenoids) and beta-lactamases inhibitors (alkyls gallates). © 2009 Nova Science Publishers, Inc. All rights reserved.SCOPUS: ch.binfo:eu-repo/semantics/publishe

Antimicrobial and antioxidant properties of Cordia gilletii (Boraginaceae)

info:eu-repo/semantics/publishe

Optimization of the culture medium used for direct TLC-bioautography. Application to the detection of antimicrobial compounds from Cordia gilletii De Wild (Boraginaceae)

TLC-bioautography, a convenient and simple mean of testing plant extracts and pure substances for their effects on pathogenic microorganisms, enables easy detection of active fractions. Its application requires a medium fluid enough to cast suspensions of microorganisms but viscous enough to adhere to the TLC plate and maintain sufficient humidity for bacterial growth. Mueller-Hinton (MH) agar and broth are often used for this purpose. These media have major drawbacks, however — microorganisms can suffer thermal shock from the temperature required for agar casting, and agar can also dilute the antimicrobial compounds, and immersion broth does not conveniently adhere to the TLC plate and dries too rapidly. To overcome these problems, we investigated several combinations of MH broth and MH agar (proportions 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 60:60, and 50:50) to discover a medium sufficiently fluid to prepare bacterial suspensions at 37°C (the temperature for optimum growth of many pathogenic bacteria) yet which solidifies at ambient temperature. The mixture MH broth-MH agar 90:10 fulfilled these requirements; media containing higher proportions of MH agar were solid at 37°C and those containing lower proportions of MH agar flowed down the plate, partly carrying the active spots, leading to poor detection and resolution. This simple modification of the culture medium can be applied to most media amenable to TLC-bioautography. This 90:10 mixture was used to detect antimicrobial compounds in a Congolese medicinal plant, Cordia gilletii De Wild (Boraginaceae), affording superior chromatographic resolution compared with MH broth alone. The active extracts were further compared by a second TLC bioassay for compounds able to quench the luminescence of Vibrio fischerii ,a bioindicator for toxicity and general biological activity.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Direct and indirect antimicrobial effects and antioxidant activity of Cordia gilletii De Wild (Boraginaceae).

Cordia gilletii De Wild (Boraginaceae) root bark is traditionally used in Democratic Republic of Congo (DRC) for the treatment of various disorders, including malaria, diarrhea, wounds and skin diseases; part of these activities may rely on antimicrobial and antioxidant properties. Successive extracts of root barks powder with n-hexane, dichloromethane, ethyl acetate, methanol and water were tested for antimicrobial activity, both direct and indirect (antibiotic resistance reversal), against 10 strains of bacteria and 1 strain of fungi by broth microdilution and agar diffusion methods. The eventual synergy between plant extracts and antibiotics was investigated by the determination of the fractional inhibitory concentration index (FIC index). The methanol extract showed direct antimicrobial activity against all tested microorganisms with minimum inhibitory concentrations (MIC) ranging between 125 and 1000 microg/ml, whereas the ethyl acetate and the dichloromethane extracts showed activity on four and three strains, respectively. 200 microg/ml of n-hexane and dichloromethane extracts decreased the MICs of penicillin and streptomycin 4-64-fold for methicillin-resistant Staphylococcus aureus. A synergistic effect was found between the methanol extract and tetracycline, whereas additive effects were observed for the other combinations tested. The methanol and dichloromethane extracts showed the greater antioxidant activity by scavenging the free radical DPPH with IC(50) values of 3.2 and 8.1 microg/ml, respectively. These results support the use of the plant in the treatment of infectious diseases and wounds; they warrant further studies as to the nature of active compounds.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Effects of Cordia gilletii extracts on methicillino-resistant Staphylococcus aureus

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Development of a suitable culture medium for TLC-bioautography. Application to the detection of antibacterial compounds from Cordia gilletii extracts

info:eu-repo/semantics/nonPublishe

Direct and indirect antimicrobial activity of Cordia gilletii extracts

info:eu-repo/semantics/publishe

Absence of pyrrolizidine alkaloids in Cordia gilletii de wild (Boraginaceae)

info:eu-repo/semantics/publishedhttp://dx.doi.org/10.1016/j.bse.2011.12.00