Chemical composition and antibacterial activities of seven Eucalyptus species essential oils leaves

BACKGROUND: In this paper, we have studied the essential oils chemical composition of the leaves of seven Eucalyptus species developed in Tunisia. Eucalyptus leaves were picked from trees growing in different arboretums in Tunisia. Choucha and Mrifeg arboretums located in Sedjnene, region of Bizerte (Choucha: E. maideni, E. astrengens et E. cinerea; Mrifeg : E. leucoxylon), Korbous arboretums located in the region of Nabeul, North East Tunisia with sub-humid bioclimate, (E. lehmani), Souiniet-Ain Drahem arboretum located in region of Jendouba (E. sideroxylon, E. bicostata). Essential oils were individually tested against a large panel of microorganisms includingStaphylococcus aureus (ATCC 6539), Escherichia coli (ATCC 25922), Enterococcus faecalis (ATCC29212), Listeria ivanovii (RBL 30), Bacillus cereus (ATCC11778). RESULTS: The yield of essential oils ranged from 1.2% to 3% (w/w) for the different Eucalyptus species. All essential oils contain α-pinene, 1,8-cineol and pinocarveol-trans for all Eucalyptus species studied. The 1,8-cineol was the major compound in all species (49.07 to 83.59%). Diameter of inhibition zone of essential oils of Eucalyptus species varied from 10 to 29 mm. The largest zone of inhibition was obtained for Bacillus cereus (E. astrengens) and the lowest for Staphylococcus aureus (E. cinerea). The essential oils from E. maideni, E. astrengens, E. cinerea (arboretum of Bizerte), E. bicostata(arboretum of Aindraham) showed the highest antibacterial activity against Listeria ivanovii and Bacillus cereus. CONCLUSION: The major constituents of Eucalyptus leaves essential oils are 1,8-cineol (49.07 to 83.59%) and α-pinene (1.27 to 26.35%). The essential oils from E. maideni, E. astrengens, E. cinerea, E. bicostatashowed the highest antibacterial activity against Listeria ivanovii and Bacillus cereus, they may have potential applications in food and pharmaceutical products.

Compositional studies and Biological activities of Perovskia abrotanoides Kar. oils

BACKGROUND: Current study has been designed to evaluate the chemical composition of essential and fixed oils from stem and leaves of Perovskia abrotanoides and antioxidant and antimicrobial activities of these oils. RESULTS: GC-MS analysis of essential oil identified 19 compounds with (E)-9-dodecenal being the major component in stem and hexadecanoic acid in leaves. In contrast, GC-MS analysis of fixed oil showed 40 constituents with α-amyrin the major component in stem and α-copaene in leaves. The antioxidant activity showed the highest value of 76.7% in essential oil from leaves in comparison with fixed oil from stem (45.9%) through inhibition of peroxidation in linoleic acid system. The antimicrobial assay tested on different microorganisms (e.g. E. coli, S. aureus, B. cereus, Nitrospira, S. epidermis, A. niger, A. flavus and C. albicans) showed the higher inhibition zone at essential oil from leaves (15.2 mm on B. cereus) as compared to fixed oil from stem (8.34 mm onS. aureus) and leaves (11.2 mm on S. aureus). CONCLUSIONS: The present study revealed the fact that essential oil analyzed from Perovskia abrotanoides stem and leaves could be a promising source of natural products with potential antioxidant and antimicrobial activities, as compared to fixed oil.

In vivo antipyretic, antiemetic, in vitro membrane stabilization, antimicrobial, and cytotoxic activities of different extracts from Spilanthes paniculata leaves

BACKGROUND: The study was conducted to evaluate the in vitro antimicrobial activity, cytotoxic, and membrane stabilization activities, and in vivo antiemetic and antipyretic potentials of ethanolic extract, n-hexane and ethyl acetate soluble fractions of Spilanthes paniculata leaves for the first time widely used in the traditional treatments in Bangladesh. RESULTS: In antipyretic activity assay, a significant reduction (P < 0.05) was observed in the temperature in the mice tested. At dose 400 mg/kg-body weight, the n-hexane soluble fraction showed the effect (36.7 ± 0.63°C ) as like as the standard (dose 150 mg/kg-body weight) after 5 h of administration. Extracts showed significant (P < 0.001) potential when tested for the antiemetic activity compared to the standard, metoclopramide. At dose 50 mg/kg-body weight, the standard showed 67.23% inhibition, whereas n-hexane and ethyl acetate soluble fractions showed 37.53% and 24.93% inhibition of emesis respectively at dose 400 mg/kg-body weight. In antimicrobial activity assay, the n-hexane soluble fraction (400 µg/disc) showed salient activity against the tested organisms. It exerts highest activity against Salmonella typhi (16.9 mm zone of inhibition); besides, crude, and ethyl acetate extracts showed resistance to Bacillus cereus and Bacillus subtilis, and Vibrio cholera respectively. All the extracts were tested for lysis of the erythrocytes. At the concentration of 1mg/ml, ethanol extract, and n-hexane and ethyl acetate soluble fractions significantly inhibited hypotonic solution induced lysis of the human red blood cell (HRBC) (27.406 ± 3.57, 46.034 ± 3.251, and 30.72 ± 5.679% respectively); where standard drug acetylsalicylic acid (concentration 0.1 mg/ml) showed 77.276 ± 0.321% inhibition. In case of heat induced HRBC hemolysis, the plant extracts also showed significant activity (34.21 ± 4.72, 21.81 ± 3.08, and 27.62 ± 8.79% inhibition respectively). In the brine shrimp lethality bioassay, the n-hexane fraction showed potent (LC50 value 48.978 µg/ml) activity, whereas ethyl acetate fraction showed mild (LC50 value 216.77 µg/ml) cytotoxic activity. CONCLUSIONS: Our results showed that the n-hexane extract has better effects than the other in all trials. In the context, it can be said that the leaves of S. paniculata possess remarkable pharmacological effects, and justify its folkloric use as antimicrobial, antipyretic, anti-inflammatory, and antiemetic agent. Therefore, further research may be suggested to find possible mode of action of the plant part.

Synthesis and biological evaluation of some new coumarin derivatives as antimicrobial agents

A series of new 7-[2-[3-alkyl/aryl-4-arylthiazol-2[3H]-ylidene]hydrazono]propoxy]-4-methyl-2H-chromen-2-ones, [6-9a-e], was prepared by the reaction of appropriate N-alkyl/aryl-2-[1-[4-methyl-2-oxo-2H-chromen-7yloxy]propan-2-ylidene]hydrazine carbothioamides [4a-d] and phenacyl bromides [5a-e]. The purity of all new compounds was checked by TLC and elucidation of their structures was confirmed by IR, [1]H NMR, and mass spectrometry along with elemental microanalyses. All the target compounds were evaluated for their possible antimicrobial activity. Most of the tested compounds showed weak to moderate antibacterial activity against most of the bacterial strains used in comparison with gatifloxacin as a reference drug. The most active compounds were 6b, 6c, 7b, 8b, 8c, and 9c against B. cereus, E. coli and S. marcescens. Results of antifungal activity revealed that all compounds showed weak to moderate activity against S. brevicaulis, while ketoconazole as a reference drug was completely inactive. Compounds 6a, 6b, 6c, 6e and 7b were even more active than ketoconazole against F. oxysporum

Phenotypic & genetic characterization of Bacillus cereus isolated from the acute diarrhoeal patients.

Background & objectives: Bacillus cereus is one of the pathogens responsible for human diarrhoea, mainly due to consumption of contaminated food. The present study was undertaken to determine the occurrence of B. cereus among diarrhoeal patients and its phenotypic and genetic characteristics that determine the virulence and clonal features. Methods: Stool specimens were collected for two years from acute diarrhoeal patients attending the two referral hospitals in Kolkata. Presence of virulence genes in B. cereus was determined by PCR. Clonality was assessed by pulsed-field gel analysis (PFGE) by restriction digestion with SmaI and NotI enzymes. Enterotoxins were detected by haemolysin assay and using BCET-RPLA kit. Invasion assay was done on Hep-2 cell line. Antimicrobial susceptibility was tested by disc diffusion method. Results: B. cereus was identified in 54 (3.5%) of the 1536 diarrhoeal cases studied. Majority of the isolates were susceptible to many antibiotics but showed resistant to amoxyclav and cephalosporins. Six genes covering the two different enterotoxic complexes determining the pathogenicity of B. cereus have been characterized by PCR. The nhe genes were detected in a higher proportion than hbl. Except in two, clonal diversity was noticed among 21 B. cereus isolates. Haemolytic enterotoxin was detected in 76 per cent of the isolates. Majority of the isolates (67%) produced in vitro enterotoxin (BCET) confirming its involvement in the infection. Interpretation & conclusions: Though the presence of B. cereus was not high in patients with diarrhoea, several virulence factors confirm their association with diarrhoea. Distinct clonality was identified in majority of the isolates indicating their origin from different sources.

Antibacterial & antiplasmid activities of Helicteres isora L.

Background & objectives: The multiple drug resistance (MDR) is a serious health problem and major challenge to the global drug discovery programmes. Most of the genetic determinants that confer resistance to antibiotics are located on R-plasmids in bacteria. The present investigation was undertaken to investigate the ability of organic extract of the fruits of Helicteres isora to cure R-plasmids from certain clinical isolates. Methods: Active fractions demonstrating antibacterial and antiplasmid activities were isolated from the acetone extracts of shade dried fruits of H. isora by bioassay guided fractionation. Minimal inhibitory concentration (MIC) of antibiotics and organic extracts was determined by agar dilution method. Plasmid curing activity of organic fractions was determined by evaluating the ability of bacterial colonies (pre treated with organic fraction for 18 h) to grow in the presence of antibiotics. The physical loss of plasmid DNA in the cured derivatives was further confirmed by agarose gel electrophoresis. Results: The active fraction did not inhibit the growth of either the clinical isolates or the strains harbouring reference plasmids even at a concentration of 400 μg/ml. However, the same fraction could cure plasmids from Enterococcus faecalis, Escherichia coli, Bacillus cereus and E. coli (RP4) at curing efficiencies of 14, 26, 22 and 2 per cent respectively. The active fraction mediated plasmid curing resulted in the subsequent loss of antibiotic resistance encoded in the plasmids as revealed by antibiotic resistance profile of cured strains. The physical loss of plasmid was also confirmed by agarose gel electrophoresis. Interpretation & conclusions: The active fraction of acetone extract of H. isora fruits cured R-plasmids from Gram-positive and Gram-negative clinical isolates as well as reference strains. Such plasmid loss reversed the multiple antibiotic resistance in cured derivatives making them sensitive to low concentrations of antibiotics. Acetone fractions of H. isora may be a source to develop antiplasmid agents of natural origin to contain the development and spread of plasmid borne multiple antibiotic resistance.

Tetracycline and oxytetracycline resistance determinants detected in Bacillus cereus strains isolated from honey samples / Detección de determinantes de resistencia a tetraciclina y oxitetraciclina en cepas de Bacillus cereus aisladas de muestras de miel

The aim of this study was to investigate the presence of tetracycline and oxytetracycline resistance determinants in Bacillus cereus strains isolated from honey samples. Of a total of 77 isolates analyzed, 30 (39%) exhibited resistance to tetracyclines according to the results of a disk diffusion method. Resistant strains (n=30) were screened by PCR for the presence of the resistant determinants tetK, tetL, tetM, tetO, tetW, otrA and otrB and their MIC values for tetracycline, oxytetracycline and minocycline were assessed. According to the PCR results, 23 isolates (77%) presented at least one tetracycline or oxytetracycline resistance determinant. The tetK genotype was present in 10 isolates while the tetL, tetM, and otrA genotypes were present in 3, 2, and 5 isolates, respectively. In addition, 2 isolates of the tetK plus tetM genotype, 1 of the tetK plus tetL genotype, and 1 of the tetK plus otrA genotype were found. All isolates were tetW, tetO and otrB negatives. On the other hand, 7 isolates (23%) showed a tetracycline-resistant and/or minocyclineresistant phenotype (MIC) but did not carry any of the tet or otr determinants investigated in this study. This research has shown that B. cereus isolates from honey samples contain a variety of tetracycline and oxytetracycline resistance genes, including the tetK and tetL determinants which encode for efflux proteins, and tetM and otrA, which encode for ribosomal protection proteins. These findings indicate that strains isolated from honeys could represent a reservoir for tetracycline resistance genes. To our knowledge, this is the first report of tetracycline-resistant and oxytetracyclineresistant B. cereus strains carrying the tetK determinant, and also the first report of oxytetracycline-resistant and tetracycline- resistant Bacillus species carrying the otrA determinant.

El objetivo del presente estudio ha sido investigar la presencia de diversos determinantes de resistencia a tetraciclina y oxitetraciclina en las poblaciones de Bacillus cereus presentes en la miel. De un total de 77 aislamientos evaluados, 30 (39%) resultaron resistentes a tetraciclina y/o minociclina de acuerdo con los resultados de las pruebas de difusión en disco. Dentro del grupo que presentó un fenotipo resistente, se investigó la presencia de los determinantes tetK, tetL, tetM, tetO, tetW, otrA y otrB por PCR y se determinaron los valores de CIM para tetraciclina, oxitetraciclina y minociclina. De acuerdo con los resultados obtenidos por PCR, 23 aislamientos (77%) presentaron al menos un determinante de resistencia a tetraciclina o a oxitetraciclina; el genotipo tetK se encontró en 10 de esos aislamientos, mientras que los genotipos tetL, tetM y otrA se hallaron en 3, 2 y 5 aislamientos, respectivamente. Ningún aislamiento presentó los genotipos tetW, tetO ni otrB. Adicionalmente, se encontraron los genotipos tetK plus tetM (2 aislamientos); tetK plus tetL (1 aislamiento) y tetK plus otrA (1 aislamiento). Por otra parte, 7 cepas (23%) resultaron resistentes a tetraciclina, oxitetraciclina y/o minociclina por CIM, pero no presentaban ninguno de los determinantes tet u otr estudiados. Estos resultados indican la existencia de un alto porcentaje de cepas de B. cereus aisladas de miel con genes de resistencia a tetraciclina y oxitetraciclina, incluyendo los determinantes tetK, tetL, tetM y otrA. Este estudio constituye el primer registro de la presencia del determinante tetK de resistencia a tetraciclina en B. cereus, como así también la presencia del determinante otrA dentro del género Bacillus.

Evaluation of toxicity of iron, chromium and cadmium on Bacillus cereus growth

High concentration of iron and other trace elements could restrict bacterial growth and modify their metabolic pattern as well. However, this study aimed to find out the influence of iron, chromium, cadmium and synergism or antagonism between these elements on the growth of a gram positive bacterium. In a series of experiments, Bucillus cereus was cultured in a nutrient broth which supplemented with Fe[+2], Fe[+3], Cr[+3], Cd[+2] separately, or in combination with each other, at 37°C for 5 hours. Bacterial growth was measured every half - hour, using spectrophotometer. The results indicated that bacterial growth rate reduced in the presence of 0.5 mM/L concentration of Fe[+2] or Fe[+3], in comparison with control and the growth of bacteria was inhibited by 1 mM/L concentration of iron. The results also revealed that Fe [III] as well as Fe [II] was toxic for bacteria. Chromium had partial inhibitory effects on the growth of bacteria and cadmium was very toxic. Cr[+3] and Cd[+] had antagonistic effect with iron on the growth of bacteria. Data obtained here provide a potentially interesting conceptual advance in toxic effects of trace elements on pathogenic bacteria

Antibacterial effects of Carica papaya fruit on common wound organisms

The purpose of the study was to investigate antibacterial activity of ripe and unripe Carica papaya on selected micro-organisms. Cultures of micro-organisms were routinely maintained in nutrient agar slants at 4 degrees C. Extracts of immature, mature and ripe Carica papaya fruit were obtained by separately grinding factions of the epicarp, endocarp and seeds and filtering them through gauze. Sensitivity tests were conducted by adding 0.06 ml of extract to agar wells (6 mm diameter) prepared from 20 ml agar seeded with 10(6) cells/ml suspension of one of the eight organisms per plate. The inoculated plates were allowed to equilibrate at 4 degrees C for 1 hour, incubated at 37 degrees C for 24 hours, and zones of inhibition measured in millimetres. Anti-bacterial activity was expressed in terms of the radius of zone of inhibition. Seed extracts from the fruit showed inhibition in the following order: B cereus > E coli > S faecalis > S aureus > P vulgaris > S flexneri. No significant difference was found in bacterial sensitivity between immature, mature and ripe fruits. No inhibition zone was produced by epicarp and endocarp extracts. Carica papaya seeds contain anti-bacterial activity that inhibits growth of gram-positive and gram-negative organisms. Observed activity was independent of stage of fruit maturity. Carica papaya has antibacterial effects that could be useful in treating chronic skin ulcers to promote healing

Cinnabarin synthesis by "Pycnoporus sanguineus" strains antimicrobial astivity against bacteria from food products

Among three strains of "Pycnosporus sanguineus", MIP 89007 produced more cinnabarin than MIP 95001 and MIP 95002. The antimicrobial activity of cinnabarin was tesred against 11 species of bacteria isolated from food. "Bacillus cereus" and "Leuconostoc plantarum" were the most sensitive to cinnabarin, being inhibited by 0.0625 mg/ml. "Klebsiella pneumonia" was the least sensitive (>4.0 mg/ml).

Inhibition of bacterial respiration by a low-molecular weight lectin, scyllin, from Scylla serrata crab hemolymph.

Interaction of plant and/or invertebrate lectins with mammalian cells and different microorganisms is well known. In the present study, we have demonstrated that scyllin, a low molecular weight (MW 4000) lectin from the edible crab Scylla serrata hemolymph, purified by GalNAc-Sepharon affinity column followed by Mono-Q ion exchanger in FPLC exhibits antimicrobial activity against Bacillus cereus and Escherichia coli by inhibiting endogenous respiration as well as exogenous glucose oxidation. In both the cases oxygen consumption has been measured in an oxygraph. Scyllin has produced 50% inhibition of endogenous respiration at a concentration of 110 micrograms/ml and 125 micrograms/ml in B. cereus and E. coli respectively. It also reduced the exogenous glucose oxidation by 50% at a concentration of 12 micrograms/ml and 80 micrograms/ml respectively in B. cereus and E. coli. From the above study the mechanism of bacterial growth inhibitory property of scyllin is suggested though the other studies such as inhibition of nucleic acid biosynthesis, cell wall biosynthesis etc. to evaluate its total mode of inhibitory action are not yet obtained.

Antimicrobial activity pf kaurenoic acid derivatives substituted on carbon-15

The antibacterial and antifungic activities of two kaurenic acids, ent kaurenoic acid and cinnamoylgrandifloric acid isolated from a hexane extract of aerial parts of Mikania laevigata, were investigated and compared with the activities of other kaurenic acid-derivatives substituted on carbon-15. Only acetylgrandifloric acid (en-kaur-16-en-15 alfa-acetyloxy-19-oic) and its epimer xylopic acid (ent-kaur-16-4n-15 beta-acetyloxy-19-oic) displayed significant antibacterial activity at concentrations >=250 microng/ml., the 15 alfa epimer being the most active