In vitro Antibacterial Activity of Aqueous and Ethanol Extracts of Aristolochia indica and Toddalia asiatica Against Multidrug-Resistant Bacteria

Bacteria have developed multidrug resistance against available antimicrobial agents. Infectious diseases caused by these multidrug-resistant bacteria are major causes of morbidity and mortality in human beings. Synthetic drugs are expensive and inadequate for the treatment of diseases, causing side effects and ineffective against multidrug-resistant bacteria. The medicinal plants are promising to have effective antimicrobial property due to presence of phytochemical compounds like alkaloids, flavanoids, tannins and phenolic compounds. The present study aimed to find the antimicrobial activity of medicinal plants against multidrug-resistant bacteria. Multidrug-resistant bacteria were identified by Kirby-Bauer disc diffusion method. Production of β-lactamases (extended spectrum β-lactamases, metallo β-lactamase and AmpC β-lactamase) were identified by combination disc method. Antibacterial activity of aqueous and ethanol extract of Aristolochia indica and Toddalia asiatica were detected by agar well diffusion assay and minimum inhibitory concentration. All bacteria used in this study showed antibiotic resistance to ≥3 antibiotics. Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis and Vibrio cholerae were found to be positive for β-lactamase production. Ethanol extract of Aristolochia indica showed more significant antibacterial activity against multidrug-resistant bacteria than Toddalia asiatica. Ethanol extracts of Aristolochia indica and Toddalia asiatica showed minimum inhibitory concentration values of 50-100 μg/ml and 100-200 μg/ml, respectively against multidrug-resistant bacteria. From this study, it was concluded that Aristolochia indica has more potential to treat multidrug-resistant bacteria than Toddalia asiatica.     

Synthesis and antimicrobial activity of long-chain 3,4-Epoxy-2-alkanones

3,4-Epoxy-2-dodecanone, a major component in the preorbital gland of the African grey duiker (Sylvicapra grimmia), showed antimicrobial activity in preliminary tests. The C₁₁ to C₁₇ homologues of this compound were prepared and their activity against several pathogenic dermal bacteria and fungi was tested. 3,4-Epoxy-2-dodecanone and 3,4-epoxy-2-tridecanone inhibited the growth of Trichophyton mentagrophytes at 25 μg/mL. Moderate inhibition of the growth of the bacteria Propionibacterium acnes and the lipophilic yeast, Pityrosporum ovale, was seen for several of the homologues.     

Antimicrobial and antibiofilm activity of LL-37 and its truncated variants against Burkholderia pseudomallei

The Gram-negative bacterium Burkholderia pseudomallei is the aetiological agent of melioidosis, which is an endemic disease in tropical areas of Southeast Asia and Northern Australia. Burkholderia pseudomallei has intrinsic resistance to a number of commonly used antibiotics and has also been reported to develop a biofilm. Resistance to killing by antimicrobial agents is one of the hallmarks of bacteria grown in biofilm. The aim of this study was to determine the antimicrobial activity and mechanisms of action of LL-37 and its truncated variants against B. pseudomallei both in planktonic and biofilm form, as LL-37 is an antimicrobial peptide that possessed strong killing activity against several pathogens. Antimicrobial assays revealed that LL-31, a truncated variant of LL-37 lacking the six C-terminus residues, exhibited the strongest killing effect. Time-kill experiments showed that 20 μM LL-31 can reach the bactericidal endpoint within 2 h. Freeze-fracture electron microscopy of bacterial cells demonstrated that these peptides disrupt the membrane and cause leakage of intracellular molecules leading to cell death. Moreover, LL-31 also possessed stronger bactericidal activity than ceftazidime against B. pseudomallei grown in biofilm. Thus, LL-31 should be considered as a potent antimicrobial agent against B. pseudomallei both in planktonic and biofilm form.     

In vitro Screening for Antioxidant,Antimicrobial, and Antidiabetic Properties of Some Korean Native Plants on Mt. Halla,Jeju Island

In this study, Prunus padus, Lonicera caerulea, Berberis amurensis, and Ribes maximowiczianum, which are mainly distributed on Mt. Halla, Jeju Island, have been investigated for their antioxidant, antimicrobial, and antidiabetic activities. The methanol extracts of R. maximowiczianum leaves and P. padus branches exhibited significant and dose-dependent antioxidant activity including electron-donation ability and reducing power. To analyze the antimicrobial activity, each extract was tested by a serial two-fold dilution method against five selected gram-positive bacteria and four gram-negative bacteria, and this suggested that P. padus branches possessed the maximum antimicrobial activity against most of the gram-positive bacteria tested. In addition, the methanol extracts of P. padus branches exhibited the highest α-glucosidase inhibitory activity with an IC₅₀ value of 1.0±0.1 μg/ml, indicating that P. padus is a promising source as a herbal medicine.     

Resveratrol enhancement staphylococcus aureus survival under levofloxacin and photodynamic treatments

Reactive oxygen species (ROS) are an efficient tool to eradicate micro-organisms owing to the capacity of these species to damage almost all types of biomolecules and to kill cells. The increase in mechanisms of antimicrobial resistance has led to the exploration of new strategies to eliminate micro-organisms that involve the production of ROS such as superoxide anion (O₂^?–) and hydrogen peroxide (H₂O₂). ROS are produced during several antimicrobial treatments, including antibiotic and photodynamic therapies. Among the natural antioxidants, resveratrol (RSV) is efficient at preventing damage from ROS, and every day more people incorporate it as a dietary or cosmetic supplement. However, the consequences of the administration of RSV during antimicrobial treatment are unknown. To investigate possible antagonistic or synergistic effects of RSV during antibiotic therapy (levofloxacin) or photodynamic therapy (visible radiation and methylene blue), killing of planktonic Staphylococcus aureus bacteria was evaluated in the presence of RSV. The results showed that the antimicrobial capacity of these therapies is significantly diminished when levofloxacin or methylene blue are co-administered with RSV, indicating that consumption of RSV during antimicrobial treatment must be, at least, cautioned. Moreover, considering the ROS antimicrobial activity of antibacterial agents, the topical addition of RSV may also affect the control of pathogens of the human body. The results presented in this article highlight the importance of the evaluation of possible antagonistic effects when an antimicrobial agent with ROS-mediated action is co-administrated with RSV.     

Clinical and economic burden of community-acquired pneumonia amongst adults in the Asia-Pacific region

Community-acquired pneumonia (CAP) is an important cause of mortality and morbidity amongst adults in the Asia-Pacific region. Literature published between 1990 and May 2010 on the clinical and economic burden of CAP amongst adults in this region was reviewed. CAP is a significant health burden with significant economic impact in this region. Chronic obstructive pulmonary disease, cardiovascular disease, diabetes mellitus and advanced age were risk factors for CAP. Aetiological agents included Streptococcus pneumoniae, Klebsiella pneumoniae, Gram-negative bacteria, Mycobacterium tuberculosis, Burkholderia pseudomallei, Staphylococcus aureus and atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae and Legionella spp.), with important differences in the prevalence of these pathogens within the region. Antibiotic resistance was significant but was not linked to excess mortality. Aetiological pathogens remained susceptible to newer antimicrobial agents. Rational antibiotic use is essential for preventing resistance, and increased surveillance is required to identify future trends in incidence and aetiology and to drive treatment and prevention strategies.     

A defensin antimicrobial peptide from the venoms of Nasonia vitripennis

Although many antimicrobial components (i.e. antimicrobial peptides) have been found in many social Hymenoptera venoms, no antimicrobial compound is purified and characterized from parasitic Hymenoptera. From the venoms of the ectoparasitic wasp, Nasonia vitripennis, a defensin-like antimicrobial peptide named defensin-NV was purified and characterized. Defensin-NV is composed of 52 amino acid residues including 6 cysteines forming 3 disulfide bridges. Its amino acid sequence is VTCELLMFGGVVGDSACAANCLSMGKAGGSCNGGLCDCRKTTFKELWDKRFG. By BLAST search, defensin-NV showed significant sequence similarity to other insect defensin antimicrobial peptides. Defensin-NV exerted strong antimicrobial activity against tested microorganisms including Gram-positive bacteria, Gram-negative bacteria and fungi. The cDNA encoding defensin-NV was cloned from the venom reservoir cDNA library of N. vitripennis. The current work firstly purified and characterized an antimicrobial peptide from parasitic Hymenoptera.     

Transferable plasmid-mediated quinolone resistance in association with extended-spectrum β-lactamases and fluoroquinolone-acetylating aminoglycoside-6'-N-acetyltransferase in clinical isolates of Vibrio fluvialis

Vibrio fluvialis, which causes cholera-like diarrhoea in humans, is one of the aetiological agents of acute diarrhoea in Kolkata, India, and is resistant to many antimicrobial agents. Two V. fluvialis isolates resistant to fluoroquinolones and β-lactam antimicrobials were found to have mutations in the quinolone resistance-determining regions (QRDRs) of GyrA at position 83 and of ParC at position 85 as well as carrying a 150 kb plasmid harbouring the quinolone resistance gene qnrA1, the ciprofloxacin-modifying enzyme-encoding gene aac(6′)-Ib-cr and genes encoding for extended-spectrum β-lactamases such as bla_SHV and bla_CTX-M-3. When this large plasmid was transferred to Escherichia coli by conjugation, the transconjugants showed a 10-75-fold increase in the minimum inhibitory concentrations of ciprofloxacin and norfloxacin. The qnrA1 gene was identified in a complex sul1-type integron in a plasmid of the transconjugants. Southern hybridisation and sequence analysis of qnrA1 and its flanking regions confirmed the presence of aac(6′)-Ib-cr and bla_CTX-M-3 but these were not associated with the sul1-type integron. Pulsed-field gel electrophoresis (PFGE) revealed that the two V. fluvialis isolates belonged to different clones. Although the presence of many qnr alleles has been reported amongst enteric bacteria in Asian countries, this is the first report on the emergence of qnrA1 in India. qnrA1 along with aac(6′)-Ib-cr and bla_CTX-M-3 genes on a mobile plasmid may spread to other bacterial species that are under the selective pressure of fluoroquinolones and β-lactam antimicrobials in this region.     

Preliminary Phytochemical Screening and Antimicrobial Studies of Lantana indica Roxb

The aim of the present study was to investigate the antimicrobial and preliminary phytochemical properties of Lantana indica Roxb. The aqueous and organic solvent (ethyl acetate and methanol) extracts from the leaves of Lantana indica (Verbenaceae) were tested against Staphylococcus aureus, Bacillus subtilis, Steptococcus pyrogens, Escherichia coli, Proteus vulgaris, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Aspergillus niger and Candida albicans by agar well diffusion method. The results showed promising antibacterial activity against the tested bacteria. Among these, methanol and aqueous extracts were found to possess a more potent inhibitory effect when compared to the ethyl acetate extract. Preliminary phytochemical analysis of extracts revealed the presence of antimicrobial compounds such as carbohydrates, proteins, tannins and flavonoidal glycosides. The result of this study validates the use of methanol and aqueous extract of this species in ethnomedicine, favouring the isolation of antibacterial agents from the leaf extract of Lantana indica.     

Novel antimicrobial peptide discovery using machine learning and biophysical selection of minimal bacteriocin domains

Bacteriocins, the ribosomally produced antimicrobial peptides of bacteria, represent an untapped source of promising antibiotic alternatives. However, bacteriocins display diverse mechanisms of action, a narrow spectrum of activity, and inherent challenges in natural product isolation making in vitro verification of putative bacteriocins difficult. A subset of bacteriocins exert their antimicrobial effects through favorable biophysical interactions with the bacterial membrane mediated by the charge, hydrophobicity, and conformation of the peptide. We have developed a pipeline for bacteriocin-derived compound design and testing that combines sequence-free prediction of bacteriocins using machine learning and a simple biophysical trait filter to generate 20 amino acid peptides that can be synthesized and evaluated for activity. We generated 28,895 total 20-mer candidate peptides and scored them for charge, α-helicity, and hydrophobic moment. Of those, we selected 16 sequences for synthesis and evaluated their antimicrobial, cytotoxicity, and hemolytic activities. Peptides with the overall highest scores for our biophysical parameters exhibited significant antimicrobial activity against Escherichia coli and Pseudomonas aeruginosa. Our combined method incorporates machine learning and biophysical-based minimal region determination to create an original approach to swiftly discover bacteriocin candidates amenable to rapid synthesis and evaluation for therapeutic use.     

Targeting Multidrug Resistant Mycobacterium tuberculosis HtrA2 with Identical Chemical Entities of Fluoroquinolones

Tuberculosis is a highly communicable and chronic respiratory disease caused by pathogenic bacterium Mycobacterium tuberculosis. The drug - resistant species of Mycobacterium tuberculosis are tough to cure due to its resistant activity toward potential drugs. Available inhibitors of tuberculosis include few antimicrobial fluoroquinolone agents like ciprofloxacin, ofloxacin, and moxifloxacin to treat resistant Mycobacterium strains. Literature study elucidates that macromolecular target namely, HtrA2 of Mycobacterium tuberculosis play a dual role of protease and chaperone. These two activities are dependent on temperature, with low temperatures promoting the chaperone function and high temperatures promoting serine protease activity. Under normal physiological conditions HtrA2 acts as a quality control factor and promotes cell survival. In the present investigation, we screened fluoroquinolone such as ciprofloxacin, moxifloxacin and ofloxacin and their analogues based on better Docking score, absorption, distribution, metabolism and excretion screening and Lipinski''s rule of 5, to find out their efficiency on resistant strain through in silico study. From the results observed, the analogues are suggested to be potent inhibitors of HtrA2 with sufficient scope for further exploration.     

Essential oils composition in two Rosmarinus officinalis L. varieties and incidence for antimicrobial and antioxidant activities

The essential oil composition of Rosmarinus officinalis var. typicus and var. troglodytorum endemic to Tunisia, and growing wild in different bioclimates, was determined by GC and GC–MS. Oils were assessed for their antimicrobial and antioxidant activity. A variation of the chemical composition attributed to varieties rather than to bioclimates was revealed. 1.8-Cineole (47.2–27.5%) and camphor (12.9–27.9%) were identified as the main constituents of var. typicus and var. troglodytorum, respectively. The principal component analysis performed on oil constituents for all the populations allowed the distinction of two distinct population groups in accordance to the varietal subdivision. Based on the determination of the diameter of inhibition and the determination of the minimum inhibitory concentration, a low to moderate antimicrobial activity according to oils was revealed against eight bacteria tested. However, oils from var. troglodytorum showed higher bactericidal effect than those from var. typicus. The oils’ antioxidant activity, determined by 1,1-diphenyl-1-picrylhydrazyl (DPPH) assay, ferric reducing (FRAP) assay and β-carotene bleaching test, was relatively high. The highest activity was found in oils from var. troglodytorum and in one population of var. typicus from the upper semi-arid bioclimate.     

Synthesis,Characterization and In Vitro Antimicrobial Evaluation of Novel Pyrazolothiazol-4(5H)-one Derivatives

Antimicrobial screening of several novel pyrazolothiazol-4(5H)-one derivatives (3a-3j) has been performed. Reaction of aromatic aldehydes with aromatic ketones yielded starting chalcones (1a-1j) which have been subsequently reacted with thiosemicarbazide for obtaining N-thiocarbamoylpyrazole derivatives (2a-2j). These were further cyclized to pyrazolothiazol-4(5H)-one derivatives (3a-3j) in the presence of ethylbromoacetate. The structures of newly synthesized compounds were confirmed by FTIR and ¹H NMR and/or MS. The in vitro antimicrobial activity of these compounds was evaluated against Gram positive bacteria, Gram negative bacteria and fungi. Their minimum inhibitory concentration was determined by tube dilution method. The results showed that most of the compounds have promising antimicrobial activity as compared to standard drugs. Among the test compounds, 2-[5(4-chlorophenyl)-3-phenyl-4,5-dihydropyrazol-1-yl]-thiazol-4(5H)-one (3e) was found to show the most potent antimicrobial activity.     

Antibacterial and antiparasitic effects of Bothrops marajoensis venom and its fractions: Phospholipase A2 and l-amino acid oxidase

Some proteins present in snake venom possess enzymatic activities, such as phospholipase A₂ and l-amino acid oxidase. In this study, we verify the action of the Bothrops marajoensis venom (BmarTV), PLA₂ (BmarPLA₂) and LAAO (BmarLAAO) on strains of bacteria, yeast, and Leishmania sp. The BmarTV was isolated by Protein Pack 5PW, and several fractions were obtained. Reverse phase HPLC showed that BmarPLA₂ was isolated from the venom, and N-terminal amino acid sequencing of sPLA₂ showed high amino acid identity with other lysine K49 sPLA₂s isolated from Bothrops snakes. The BmarLAAO was purified to high molecular homogeneity and its N-terminal amino acid sequence demonstrated a high degree of amino acid conservation with others LAAOs. BmarLAAO was able to inhibit the growth of P. aeruginosa, C. albicans and S. aureus in a dose-dependent manner. The inhibitory effect was more significant on S. aureus, with a MIC = 50 μg/mL and MLC = 200 μg/mL. However, the BmarTV and BmarPLA₂ did not demonstrate inhibitory capacity. BmarLAAO was able to inhibit the growth of promastigote forms of L. chagasi and L. amazonensis, with an IC₅₀ = 2.55 μg/mL and 2.86 μg/mL for L. amazonensis and L. chagasi, respectively. BmarTV also provided significant inhibition of parasitic growth, with an IC₅₀ of 86.56 μg/mL for L. amazonensis and 79.02 μg/mL for L. chagasi. BmarPLA₂ did not promote any inhibition of the growth of these parasites. The BmarLAAO and BmarTV presented low toxicity at the concentrations studied. In conclusion, whole venom as well as the l-amino acid oxidase from Bothrops marajoensis was able to inhibit the growth of several microorganisms, including S. aureus, Candida albicans, Pseudomonas aeruginosa, and Leishmania sp.     

Synergy of fosfomycin with other antibiotics for Gram-positive and Gram-negative bacteria

Background

The alarming increase in drug resistance and decreased production of new antibiotics necessitate the evaluation of combinations of existing antibiotics. Fosfomycin shows no cross-resistance to other antibiotic classes. Thus, its combination with other antibiotics may potentially show synergy against resistant bacteria.

Objective

To evaluate the available published evidence regarding the in vitro synergistic activity of fosfomycin with other antibiotic agents against Gram-positive and Gram-negative bacteria.

Methods

PubMed and the Cochrane Library were searched.

Results

Forty-one studies, including 34 (82.9%) conducted/published before 2000, were eligible for inclusion. The relatively limited number of isolates examined and the considerable heterogeneity of the retrieved studies regarding the definitions of synergy and the methodologies used hamper conclusive remarks for specific combinations of fosfomycin with other antibiotics. Yet, in the 27 studies providing data for Gram-positive strains (16 for Staphylococcus aureus, 3 for coagulase-negative staphylococci, 5 for Streptococcus pneumoniae, and 3 for Enterococcus spp.), fosfomycin showed synergy against methicillin-resistant Staphylococcus aureus when combined with cefamandole, cephazolin, ceftriaxone, ciprofloxacin, imipenem, and rifampicin. Data regarding Gram-negative strains reported from 15 studies (12 exclusively for P. aeruginosa, 2 exclusively for Enterobacteriaceae, 1 for both, and 1 for Acinetobacter baumannii) suggested that fosfomycin showed an estimable synergistic effect with gentamicin, amikacin, ceftazidime, cefepime, ciprofloxacin, levofloxacin, and aztreonam against P. aeruginosa.

Conclusions

The synergistic combination of fosfomycin with other antibiotics may be a useful alternative treatment option for Gram-negative and Gram-positive infections. Additional studies using more stringent definitions of synergy, and studies reporting on the clinical efficacy of fosfomycin combinations in the current era of high antimicrobial resistance are needed.     

Antimicrobial Activity of Terminalia catappa, Manilkara zapota and Piper betel Leaf Extract

Aqueous and methanol extract of the leaves of Terminalia catappa L., Manilkara zapota L. and Piper betel L. were evaluated for antibacterial activity against 10 Gram positive, 12 Gram negative bacteria and one fungal strain, Candida tropicalis. Piperacillin and gentamicin were used as standards for antibacterial assay, while fluconazole was used as standard for antifungal assay. The three plants showed different degree of activity against the microorganisms investigated. The methanolic extract was considerably more effective than aqueous extract in inhibiting the investigated microbial strains. The most active antimicrobial plant was Piper betel.     

Bacteriocin production and distribution of bacteriocin-encoding genes in enterococci from dogs

Many enterococcal strains produce bacteriocins, which could be useful as natural food preservatives through inhibition of pathogenic and spoilage microorganisms. There is little knowledge of the distribution and spectrum of bacteriocin activity and the distribution of bacteriocin-encoding genes in enterococci isolated from dogs. Therefore, we subjected 160 enterococcal isolates (E. faecium n=92, E. faecalis n=35, E. hirae n=28, E. casseliflavus n=3, E. mundtii n=2) from 105 samples of dog faeces to polymerase chain reaction (PCR) detection of genes for enterocin A, P, B, L50A, L50B, AS-48, and bac31 and to screening for bacteriocin activity. The results showed the presence of at least one of the tested genes in 54/160 isolates, with E. faecium the most common gene-possessing species. The most frequently occurring gene for production of enterocin A was observed in combination with enterocin P and B. Bacteriocin activity was observed in 76/160 isolates against at least one of 5 indicator bacteria from the genus Listeria, Enterococcus, Streptococcus and Staphylococcus. Four selected strains (IK25, Bri, I/Dz, P10) were active mostly against different species of Enterococcus (in the range 400-25 600 AU/mL) and Listeria sp. (800-12 800 AU/mL) but no Gram-negative bacteria were inhibited. Protein character, thermostability (up to 121°C) and stability at different pH values (3.0–10.0) were confirmed for crude bacteriocins of these four strains. The antimicrobial substance of E. faecium IK25 strain was identified as enterocin B using molecular weight detection and the presence of genes.     

High burden of antimicrobial resistance in Asia

Pseudomonas aeruginosa is a nosocomial and community-acquired pathogen associated with considerable patient morbidity and mortality. Multidrug resistance in P. aeruginosa is a concern owing to the limited therapeutic options available to treat infections due to this organism. In this study, rates of antimicrobial resistance of P. aeruginosa isolates collected by The Surveillance Network Database-USA (Eurofins Medinet, Chantilly, VA) from 1997 to 2009 were examined. The patient population and specimens were stratified according to patient setting and age as well as specimen source. Multidrug resistance was defined as resistance to three or more of the following antimicrobial agents: aztreonam; cefepime; ciprofloxacin; imipenem; gentamicin; and piperacillin/tazobactam (TZP). A total of 924 740 P. aeruginosa isolates were examined in this study. Changes in resistance rates to individual antimicrobial agents were <5% for all agents except ciprofloxacin. There was a statistically significant decreasing rate of multidrug-resistant P. aeruginosa to four, five and six antimicrobial agents. For isolates resistant to imipenem, aztreonam and gentamicin, ciprofloxacin had the highest cross-resistance rates. The greatest coverage against P. aeruginosa was by the combination of TZP plus amikacin (94%) followed by aztreonam plus amikacin (90%). Pseudomonas aeruginosa resistance rates remained steady or minimally declined to all antimicrobials from 1997 to 2009. Amongst the β-lactams, TZP has the greatest activity against P. aeruginosa.     

Evaluation of microalgae and cyanobacteria as potential sources of antimicrobial compounds

In recent decades, marine microorganisms have become known for their ability to produce a wide variety of secondary bioactive metabolites. Several compounds have been isolated from marine microorganisms for the development of novel bioactives for the food and pharmaceutical industries. In this study, a number of microalgae were evaluated for their antimicrobial activity against gram-positive and gram-negative bacteria, including food and plant pathogens, using various extraction techniques and antimicrobial assays. Disc diffusion and spot-on-lawn assays were conducted to confirm the antimicrobial activity. To measure the potency of the extracts, minimum inhibition concentrations (MIultCs) were measured. Three microalgae, namely Isochrysis galbana, Scenedesmus sp. NT8c, and Chlorella sp. FN1, showed strong inhibitory activity preferentially against gram-positive bacteria. These microalgal species were then selected for further purification and analysis, leading to compound identification. By using a mixture of different chromatography techniques gas chromatography–mass spectrometry (GC–MS) and high-performance liquid chromatography (HPLC) and ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS), we were able to separate and identify the dominant compounds that are responsible for the inhibitory activity. Additionally, nuclear magnetic resonance (NMR) was used to confirm the presence of these compounds. The dominant compounds that were identified and purified in the extracts are linoleic acid, oleic acid, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These compounds are the potential candidates that inhibit the growth of gram-positive bacteria. This indicates the potential use of microalgae and their antimicrobial compounds as biocontrol agents against food and plant pathogens.     

Essential oil of the leaves of Eugenia uniflora L.: Antioxidant and antimicrobial properties

Essential oil (EO) of the leaves of Eugenia uniflora L. (Brazilian cherry tree) was evaluated for its antioxidant, antibacterial and antifungal properties. The acute toxicity of the EO administered by oral route was also evaluated in mice. The EO exhibited antioxidant activity in the DPPH, ABTS and FRAP assays and reduced lipid peroxidation in the kidney of mice. The EO also showed antimicrobial activity against two important pathogenic bacteria, Staphylococcus aureus and Listeria monocytogenes, and against two fungi of the Candida species, C. lipolytica and C. guilliermondii. Acute administration of the EO by the oral route did not cause lethality or toxicological effects in mice. These findings suggest that the EO of the leaves of E. uniflora may have the potential for use in the pharmaceutical industry.