Antibacterial activity of crude methanolic extract and its fractions of aerial parts of Anthemis tinctoria

The antibacterial activity of the methanolic extract and its fractions of aerial parts of Aniheinis tinctoria (Asteraceae) was investigated against representative gram-positive Staphylococcus aureus (ATCC 25923) and Enterococcus faecalis (ATCC 29212) and gram-negative strains Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC 27853). The activity was concentrated mainly in the dichloromethane (DCM) and hexane fractions of crude methanolic extract. The 5 mg of DCM extract per disk produced 15-16 mm of inhibition zone against S. aureus and P. aeruginosa, however, no activity was found against E. faecalis and E. coli. The hexane fraction showed activity against S. aureus, P. aeruginosa and E. faecalis. As DCM fraction showed the highest antibacterial activity in the disk diffusion assay, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of only this fraction was determined against S. aureus and P. aeruginosa. These values were found to be in the range of 1.25 to 10 mg/ml.     

Antimicrobial and antiviral screening of novel indole carboxamide and propanamide derivatives

A few series of indole derivatives were screened for antimicrobial, antifungal and anti-HBV activities. The compounds were tested for their in vitro antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and for their antifungal activity against Candida albicans using a disc diffusion method, which measures the diameter of the inhibition zone around a paper disc soaked in a solution of the test compounds. The antimicrobial activity results showed that all compounds are as a active as the standard compound ampicillin against Staphylococcus aureus. It was also found that indole carboxamide derivatives, substituted at 3-position with several benzyl groups, showed better inhibition of Bacillus subtilis than their congeners substituted at 2-position. Activity patterns of the compounds against Escherichia coli and Staphylococcus aureus were found slightly different by the same method. In this case, there was no correlation between structure and activity of the compounds. The antifungal activity of carboxamide derivatives was found higher compared to that of the propanamide derivatives. The minimum inhibitory concentration (MIC) values of some indole derivatives were also determined by the tube dilution technique. The MIC values of the compounds were found nearly 20- to 100-fold smaller compared to the standard compounds ciprofloxacin and ampicillin (1.56-3.13 microg/ml and 1.56-12.5 microg/ml, respectively) against Staphylococcus aureus, Bacillus subtilis and Escherichia coli. The MIC values of the tested compounds showed that these are better inhibitors for Candida albicans. Indole derivatives were screened by the anti-HBV susceptibility test. No compound showed good inhibition against the HBV virus.     

Antimicrobial evaluation of indole-containing hydrazone derivatives

There has been an increasing importance of drug-resistant pathogens in clinical microbiological and antibacterial research. Indoles and hydrazone-type compounds constitute important classes of compounds in the search for effective agents against multidrug-resistant microbial infections. In this study a series of 1-methylindole-3-carboxaldehyde hydrazone derivatives were evaluated for their in vitro antimicrobial activities using the two-fold serial dilution technique against Staphylococcus aureus, methicillin-resistant S. aureus, methicillin-resistant S. aureus isolate, Escherichia coli, Bacillus subtilis, and Candida albicans. The minimum inhibitory concentration (MIC) of the test compounds and the reference standards sultamicillin, ampicillin, fluconazole, and ciprofloxacin was determined. All compounds possessed a broad spectrum of activity having MIC values of 6.25-100 microg/ml against the tested microorganisms. Aromaticity and disubstitution of the phenyl ring with especially fluorine and chlorine atoms were found to be significant for the antimicrobial activity     

Synthesis and biological evaluation of new N-(2-hydroxy-4(or 5)-nitro/aminophenyl)benzamides and phenylacetamides as antimicrobial agents

A new series of N-(2-hydroxy-4(or 5)-nitro/aminophenyl)benzamide and phenylacetamide derivatives (1a-1n, 2a-2n) were synthesized and evaluated for antibacterial and antifungal activities against Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, and their drug-resistant isolate. Microbiological results indicated that the compounds possessed a broad spectrum of activity against the tested microorganisms at MIC values between 500 and 1.95 microg/ml. Benzamide derivative 1d exhibited the greatest activity with MIC values of 1.95, 3.9, and 7.8 microg/ml against drug-resistant B. subtilis, B. subtilis, and S. aureus, respectively.     

Antibacterial and cytotoxic activity of Brazilian plant extracts--Clusiaceae

Twelve extracts obtained from nine plants belonging to six different genera of Clusiaceae were analyzed against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Enterococcus faecalis) bacteria using the microdilution broth assay. Tovomita aff. longifolia, T. brasiliensis, Clusia columnaris, Garcinia madruno, Haploclathra paniculata, and Caraipa grandifolia extracts showed significant results against the bacteria. The organic extract obtained from the leaves of T. aff. longifolia showed minimal inhibitory concentration (MIC) = 70 microg/ml and minimal bactericidal concentration (MBC) = 90 microg/ml against E. faecalis and the organic extract made with the stem of C. columnaris showed MIC = 180 microg/ml and MBC = 270 microg/ml against P. aeruginosa. None of the antibacterial extracts showed lethal activity against brine shrimp nauplii. On the other hand, both aqueous and organic extracts obtained from the aerial organs of Vismia guianensis that were cytotoxic to brine shrimp nauplii did not show a significant antibacterial activity in the assay.     

Synthesis and antibacterial activity of substituted 1,2,3,4-tetrahydropyrazino [1,2-a] indoles

A series of substituted 1,2,3,4-tetrahydropyrazino [1,2-a] indole derivatives have been synthesized and tested against the Gram positive and Gram negative strains of bacteria namely Staphylococcus aureus (MTCCB 737), Salmonella typhi (MTCCB 733), Pseudomonas aeruginosa (MTCCB 741), Streptomyces thermonitrificans (MTCCB 1824) and Escherichia coli (MTCCB 1652). All synthesized compounds showed mild to moderate activity. However, compounds 4d-f were found to have potent activity against pathogenic bacteria used in the study. Their MIC ranged from 3.75 to 60 microg/disc. In vitro toxicity tests demonstrated that toxicity of 4d-f was not significantly different than that of gentamycin. However, at higher concentration (1000-4000 microg/ml) difference was highly significant.     

Antibacterial activity of coumarins

The antibacterial activity of coumarin per se and other 45 coumarin derivatives was tested against strains of Bacillus cereus MIP 96016, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Staphylococcus aureus ATCC 25923. The inhibitory effects of coumarins were affected by their substitution patterns. Osthenol (44) showed the most effective antibacterial activity against Gram-positive bacteria with MIC values ranging between 125 and 62.5 microg/ml. These results suggested that the prenyl chain of 44 at position 8 and the presence of OH at position 7 of the benzenic ring are required for the antibacterial activity against these strains.     

Antimicrobial activity of organic extracts isolated from Aplysina fistularis (Demospongiae: Aplysinidae)

Organic extracts of the sponge Aplysina fistularis (Pallas 1766) were tested for antimicrobial activity against Gram positive bacteria (Staphylococcus aureus) and Gram negative bacteria (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa). The minimal inhibitory concentration (MIC) and toxic activity of extract were determined. Susceptibility trials of organic fractions obtained by VLC: Hexane, EtOAc and CHCl3 showed that EtOAc fraction has antibacterial activity against E. coli, while CHCl3 fraction inhibited E. coli and S. aureus growth. The later refractioning of EtOAc fraction and the biodirected assays showed that fractions F12 and F13 of EtOAc/Hex and EtOAc F14 were bioactive against Gram positive and Gram negative bacteria. Only EtOAc/MeOH Sf2 from subfractionig of EtOAc F14 produced inhibition for E. coli and S. aureus. In Sf2 EtOAc/MeOH, MIC was moderate for S. aureus (MIC > 256 g/ml). F4 CHCl3/MeOH produced a high inhibition in S. aureus (MIC = 0.125 g/ml) and for E. coli (MIC > 16 g/ml). F10 CHCl3/MeOH showed a moderate activity against S. aureus (MIC > 128 g/ml) and low activity against E. coli (MIC = 512 g/ml). F10 CHCL3/MeOH did no present toxic activity against Artemia salina. The fractiorts F4 CHCL3/MeOH and Sf2 EtOAc/MeOH were toxic for this organism when the concentration was higher than 100 microg/ml. LC50 in both cases was 548.4 and 243.4 microg/ml respectively. Secondary metabolites of medium polarity obtained from A. fistularis have a wide spectrum of anti bacterial activity. Toxicity analysis suggests that only F10 CHCL3/MeOH has potential as an antimicrobial agent for clinical use.     

The effects of charge and lipophilicity on the antibacterial activity of undecapeptides derived from bovine lactoferricin.

We have investigated the effects of charge and lipophilicity on the antibacterial activity of an undecapeptide (FKCRRWQWRMK) derived from the sequence of bovine lactoferricin. We prepared ten analogues that were modified by the incorporation of Ala, Tyr, Trp, Met and Arg residues, which are amino acids known to be important for the antibacterial activity of longer derivatives of lactoferricins. All undecapeptides contained the native Trp residues in positions 6 and 8, and the Arg residues in positions 5 and 9. Generally, the Gram-positive bacterium Staphylococcus aureus was more susceptible to these undecapeptides than the Gram-negative bacteria, and a higher antibacterial activity was observed against Escherichia coli than against Pseudomonas aeruginosa. The only exception was the peptide Undeca 9 (RRWYRWAWRMR-NH2), which was almost equally active against all three test strains, displaying minimal inhibitory concentrations of 10 microg/ml (5.8 microM), 7.5 microg/ml (4.4 microM) and 5 microg/ml (2.9 microM) against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, respectively. The peptides Undeca 6 (YRAWRWAWRWR-NH2) and Undeca 7 (YRMWRWAWRWR-NH2) were the two most active undecapeptides against Staphylococcus aureus, both displaying a minimal inhibitory concentration of 2.5 microg/ml (1.5 microM). The study showed that a level was reached in which undecapeptides having a net charge above +4 and containing three or four Trp residues all displayed a high antibacterial activity. All undecapeptides prepared were essentially non-haemolytic, but undecapeptides containing more than three Trp residues displayed 50% haemolysis of human red blood cells at concentrations above 400 microg/ml (>230 microM).     

Antibacterial activity of snake, scorpion and bee venoms: a comparison with purified venom phospholipase A2 enzymes

AIMS: Venoms of snakes, scorpions, bees and purified venom phospholipase A(2) (PLA(2)) enzymes were examined to evaluate the antibacterial activity of purified venom enzymes as compared with that of the crude venoms. METHODS AND RESULTS: Thirty-four crude venoms, nine purified PLA(2)s and two L-amino acid oxidases (LAAO) were studied for antibacterial activity by disc-diffusion assay (100 microg ml(-1)). Several snake venoms (Daboia russelli russelli, Crotalus adamanteus, Naja sumatrana, Pseudechis guttata, Agkistrodon halys, Acanthophis praelongus and Daboia russelli siamensis) showed activity against two to four different pathogenic bacteria. Daboia russelli russelli and Pseudechis australis venoms exhibited the most potent activity against Staphylococcus aureus, while the rest showed only a moderate activity against one or more bacteria. The order of susceptibility of the bacteria against viperidae venoms was -S. aureus > Proteus mirabilis > Proteus vulgaris > Enterobacter aerogenes > Pseudomonas aeruginosa and Escherichia coli. The minimum inhibitory concentrations (MIC) against S. aureus was studied by dilution method (160-1.25 microg ml(-1)). A stronger effect was noted with the viperidae venoms (20 microg ml(-11)) as compared with elapidae venoms (40 microg ml(-1)). The MIC were comparable with those of the standard drugs (chloramphenicol, streptomycin and penicillin). CONCLUSION: The present findings indicate that viperidae (D. russelli russelli) and elapidae (P. australis) venoms have significant antibacterial effects against gram (+) and gram (-) bacteria, which may be the result of the primary antibacterial components of laao, and in particular, the PLA(2) enzymes. The results would be useful for further purification and characterization of antibacterial agents from snake venoms. SIGNIFICANCE AND IMPACT OF THE STUDY: The activity of LAAO and PLA(2) enzymes may be associated with the antibacterial activity of snake venoms.     

In vitro antibacterial activity of laboratory grown culture of Spirulina platensis

The hexane, ethyl acetate, dichloromethane, methanol extracts and spent media (extracellular substances) were tested in vitro for their antibacterial activity for which one Gram-positive bacterium (Staphylococcus aureus) and four Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumoniae) were used as test organisms. The methanol extract showed more potent activity than other organic extracts, spent medium of the culture exhibited little activity against E. coli only. No inhibitory effect was found against Klebsiella pneumoniae.The broth microdilution assay gave minimum inhibitory concentrations (MIC) values ranging from 1 to 512 μg/ml. The MIC of methanol extract against S. aureus and E. coli were 128 μg/ml and 256 μg/ml, respectively.     

Antiviral and antimicrobial assessment of some selected flavonoids

In the current study, the results of antibacterial, antifungal, and antiviral activity tests of four flavonoid derivatives, scandenone (1), tiliroside (2), quercetin-3,7-O-alpha-L-dirhamnoside (3), and kaempferol-3,7-O-alpha-L-dirhamnoside (4), are presented. Antibacterial and antifungal activities of these compounds were tested against Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumoniae, Acinetobacter baumannii, Staphylococcus aureus, Bacillus subtilis, and Enterococcus faecalis, as well as the fungus Candida albicans by a micro-dilution method. On the other hand, both DNA virus Herpes simplex (HSV) and RNA virus Parainfluenza-3 (PI-3) were employed for antiviral assessment of the compounds using Madin-Darby bovine kidney and Vero cell lines. According to our data, all of the compounds tested were found to be quite active against S. aureus and E. faecalis with MIC values of 0.5 microg/ml, followed by E. coli (2 microg/ml), K. pneumoniae (4 microg/ml), A. baumannii (8 micro/g/ml), and B. subtilis (8 microg/ml), while they inhibited C. albicans at 1 microg/ml as potent as ketoconazole. However, only compound 3 displayed an antiviral effect towards PI-3 in the range of 8-32 microg/ml of inhibitory concentration for cytopathogenic effect (CPE).     

Synthesis, antibacterial activities and molecular docking studies of Schiff bases derived from N-(2/4-benzaldehyde-amino) phenyl-N'-phenyl-thiourea

A series of novel Schiff base derivatives have been designed and synthesized, and their biological activities were also evaluated as potential inhibitors of FabH. These compounds were assayed for antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Compounds with potent antibacterial activities were tested for their E. coli FabH inhibitory activity. Compound 3v showed the most potent antibacterial activity with MIC of 1.56-6.25 μg/mL against the tested bacterial strains and exhibited the most potent E. coli FabH inhibitory activity with IC(50) of 4.3 μM. Docking simulation was performed to position compound 3v into the E. coli FabH active site to determine the probable binding conformation.     

Antimicrobial activity of hydrophobic xanthones from Cudrania cochinchinensis against Bacillus subtilis and methicillin-resistant Staphylococcus aureus

Ten xanthones with one or two isoprenoid groups and a prenylated benzophenone isolated from roots of Cudrania cochinchinensis (Moraceae) were tested for their antimicrobial activities against Bacillus subtilis and methicillin-resistant Staphylococcus aureus (MRSA). Among these compounds, gerontoxanthone H exhibited considerable antibacterial activity against B. subtilis (MIC = 1.56 microg/ml). Four xanthones, gerontoxanthone I, toxyloxanthone C, cudraxanthone S, and 1,3,7-trihydroxy-2-prenylxanthone, showed weak antibacterial activity against the bacterium (MICs = 3.13-6.25 microg/ml). These compounds also exhibited similar MIC values against methicillin-sensitive S. aureus, MRSAs, and Micrococcus luteus.     

Antibacterial abietane-type diterpenoid, taxodone from Metasequoia glyptostroboides Miki ex Hu

In an attempt to isolate bioactive constituents, ethyl acetate cone extract of Metasequoia glyptostroboides was subjected to a column chromatographic analysis that resulted in isolation of an abietane-type diterpenoid, taxodone. Its structure was elucidated by spectroscopic means. Further, taxodone showed potential antibacterial effect as diameters of zones of inhibition against foodborne pathogenic bacteria, such as Listeria monocytogenes ATCC 19166, Salmonella typhimurium KCTC 2515, S. enteritidis KCTC 2021, Escherichia coli ATCC 8739, E. coli O157:H7 ATCC 43888, Enterobacter aerogenes KCTC 2190, Staphylococcus aureus ATCC 6538 and S. aureus KCTC 1916, were found in the range of 9.4 to 14.2 mm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of taxodone against the employed bacterial pathogens were found in the range of 250 to 1000 and 250 to less than 2000 microg/ml, respectively. Also the compound had a strong antibacterial effect on the viable counts of the tested bacteria. These findings indicate that the bioactive compound taxodone present in M. glyptostroboides could be used as an antibacterial agent in food industry to inhibit the growth of certain important foodborne pathogens.     

Antibacterial compounds from Carissa lanceolata R.Br

The dichloromethane extract of the wood of Carissa lanceolata R.Br. (Apocynaceae) afforded the eudesmanes carissone, dehydrocarissone and carindone. This is the first account of carissone being isolated from the wood of C. lanceolata, and of carindone being isolated from this Carissa species. Dehydrocarissone has not been isolated previously from any Carissa species. The antibacterial activity of these natural products were examined against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. All three compounds showed activity, with dehydrocarissone and carindone having a minimum inhibitory concentration less than 0.5 mg/ml against S. aureus and E. coli.     

Antibacterial activity of isoflavonoids isolated from Erythrina variegata against methicillin-resistant Staphylococcus aureus

AIMS: To screen 16 isoflavonoids isolated from Erythrina variegata (Leguminosae) for their antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). METHODS AND RESULTS: The roots of E. variegata were macerated with acetone. The chloroform-soluble fraction of the residue was subjected to repeated silica gel column chromatography followed by elution with various solvents. Structures of the isolated compounds were determined by extensive spectroscopic studies. Each compound was dissolved in dimethyl sulphoxide and added to agar plates (final concentration 1.56-100 microg ml(-1) and suspensions of MRSA spotted onto the agar plates to determine the minimum inhibitory concentration (MIC). Repeated silica gel chromatography yielded 16 compounds and spectroscopic studies revealed that all were isoflavonoids. Whilst 14 compounds showed antibacterial activity in this concentration range, the MIC values varied significantly among them. Of the active compounds, 3,9-dihydroxy-2,10-di(gamma,gamma-dimethylallyl)-6a,11a-dehydropterocarpan (erycristagallin) and 9-hydroxy-3-methoxy-2-gamma,gamma-dimethylallylpterocarpan (orientanol B) exhibited the highest activity with MIC values of 3.13-6.25 microg ml(-1). CONCLUSIONS: Erycristagallin and orientanol B showed the highest anti-MRSA activity (3.13-6.25 microg ml(-1). SIGNIFICANCE AND IMPACT OF THE STUDY: Erycristagallin and orientanol B could be leading compounds for phytotherapeutic agents against MRSA infections.     

Metalloantibiotics: synthesis, characterization and in-vitro antibacterial studies on cobalt (II), copper (II), nickel (II) and zinc (II) complexes with cloxacillin

The synthesis and characterization of cloxacillin (clox) complexes with divalent metal ions [Co (II), Cu (II), Ni (II) and Zn (II)] is described. The nature of bonding of the chelated cloxacillin and the structures of the metal complexes have been elucidated on the basis of their physical and spectroscopic data. In all the complexes, the cloxacillin acts as a uninegatively charged bidentate ligand with coordination involving the carboxylate-O and endocyclic-N of the beta-lactam ring. The new compounds have been screened for in-vitro antibacterial activity against Escherichia coli (a), Klebsiella pneumonae (b), Proteus mirabilis (c), Pseudomonas aeruginosa (d), Salmonella typhi (e), Shigella dysentriae (f), Bacillus cereus (g), Corynebacterium diphtheriae (h), Staphylococcus aureus (j) and Streptococcus pyogenes (k) bacterial strains. The brine shrimp bioassay was also carried out to study their in-vitro cytotoxic properties. All compounds, respectively, showed a promising activity (90%) against five bacterial species at 10 microg/ml concentration and a significant activity (52%) against the same test bacteria at 25 microg/ml concentration.     

Synthesis, molecular modeling and biological evaluation of β-ketoacyl-acyl carrier protein synthase III (FabH) as novel antibacterial agents

A series of novel cinnamic acid secnidazole ester derivatives have been designed and synthesized, and their biological activities were also evaluated as potential inhibitors of FabH. These compounds were assayed for antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Compounds with potent antibacterial activities were tested for their E. coli FabH inhibitory activity. Compound 3n showed the most potent antibacterial activity with MIC of 1.56-6.25 μg/mL against the tested bacterial strains and exhibited the most potent E. coli FabH inhibitory activity with IC?? of 2.5 μM. Docking simulation was performed to position compound 3n into the E. coli FabH active site to determine the probable binding conformation.     

Antibacterial activity of Ocimum gratissimum L. essential oil.

The essential oil (EO) of Ocimum gratissimum inhibited Staphylococcus aureus at a concentration of 0.75 mg/ml. The minimal inhibitory concentrations (MICs) for Shigella flexineri, Salmonella enteritidis, Escherichia coli, Klebsiella sp., and Proteus mirabilis were at concentrations ranging from 3 to 12 microg/ml. The endpoint was not reached for Pseudomonas aeruginosa (>=24 mg/ml). The MICs of the reference drugs used in this study were similar to those presented in other reports. The minimum bactericidal concentration of EO was within a twofold dilution of the MIC for this organism. The compound that showed antibacterial activity in the EO of O. gratissimum was identified as eugenol and structural findings were further supported by gas chromatography/mass spectra retention time data. The structure was supported by spectroscopic methods.