Investigation of the antibacterial and antifungal activity of thiolated naphthoquinones

The WHO has stated that antibiotic resistance is escalating to perilously high levels globally and that traditional therapies of antimicrobial drugs are futile against infections caused by resistant microorganisms. Novel antimicrobial drugs are therefore required. We report in this study on the inhibitory activity of the 1,4-naphthoquinone-2,3-bis-sulfides and 1,4-naphthoquinone sulfides against two bacteria and a fungus to determine their antimicrobial properties. The 1,4-naphthoquinone sulfides have potent activity with a minimum inhibitory concentration (MIC) of 7.8 μg/mL against Staphylococcus aureus (Gram +ve), an MIC of 23.4 μg/mL against the fungus, Candida albicans, which was better than that of Amphotericin B (MIC = 31.3 μg/mL), and against Escherichia coli (Gram −ve) an MIC of 31.3 μg/mL was obtained. The 1,4-naphthoquinone had an MIC of 11.7 μg/mL against S. aureus and the 1,4-naphthohydroquinone also had the same activity against E. coli.

Investigation of the antimicrobial and anticancer activity of aminonaphthoquinones

In this study, we report on the inhibitory activity of synthesized aminonaphthoquinones against two bacterial and one fungal species to determine their antimicrobial properties. A minimum inhibitory concentration (MIC) of 7.8 μg/mL was obtained against the fungus, Candida albicans, which was better than that of Amphotericin B (MIC = 31.25 μg/mL). Escherichia coli (Gram -), was inhibited at a MIC of 23.4 μg/mL and Staphylococcus aureus (Gram +) at a MIC of 31.3 μg/mL. The aminonaphthoquinones were also screened against HCT116 colon, PC3 prostate and HepG2 liver cancer cell lines to evaluate their cytostatic effects. They had potent activity (GI₅₀ = 5.87–9.90 μM) which was about three-6-fold better than that of parthenolide (GI₅₀ = 25.97 μM) against the prostate cancer cell line. These compounds were generally more selective for cancer cells than for normal human lung fetal fibroblasts (WI-38).     

Antibacterial activity of leaf extracts of Pongamia pinnata from India

This study was designed to examine the efficacy of various organic extracts derived from the leaves of Pongamia pinnata (L.) Pierre (Fabaceae) for antibacterial potential against some representative food spoilage and food-borne pathogenic bacteria. The organic extracts of chloroform, ethyl acetate and methanol, at a concentration of 2500 μg/mL, exhibited a promising antibacterial effect against Bacillus subtilis ATCC6633, Staphylococcus aureus ATCC6538, Listeria monocytogenes ATCC19118, L. monocytogenes ATCC19166, Pseudomonas aeruginosa ATCC6432 and Salmonella typhimurium ATCC2512. The zones of inhibition of various leaf extracts against the tested bacterial pathogens were found in the range of 8.1 to 18?mm, along with their respective MIC values, ranging from 125 to 1000 μg/mL. The chloroform, ethyl acetate and methanol extracts displayed significantly higher antibacterial activity as compared to streptomycin. The results of this study suggest that P. pinnata may have potential use in food industry as an antimicrobial agent, as well as pharmaceutical interest.     

Alignment-based design and synthesis of new antimicrobial Aurein-derived peptides with improved activity against Gram-negative bacteria and evaluation of their toxicity on human cells

Considering the worldwide increasing prevalence of resistance to traditional antibiotics, it is necessary to find new antibiotics to deal with this issue. Recently, antimicrobial peptides (AMPs) have been proposed as new antimicrobial agents. Aureins are a family of AMPs that are isolated from Green and Golden Bell Frogs. These peptides have a favorable antibacterial activity against Gram-positive bacteria. We designed two peptides derived from natural Aurein enjoying alignment-based design method. After synthesis of the peptides, their secondary structure was checked by circular dichroism. Consequently, the antibacterial effects of these peptides were investigated by determining the minimum inhibitory concentration (MIC) and bactericidal concentration. Eventually, the toxicity of these peptides was determined by MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) assay on normal human skin cells (Hu02 cell line). Natural Aurein1.2 was used as a natural control to compare the properties in all stages. The results indicated that these new peptides had medium-upward antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis (MIC of 8–64 μg/mL) and weak bactericidal activity against Staphylococcus aureus (MIC of 128–256 μg/mL). Also, MTT assays results showed that AureinN2 is less toxic than AureinN1 and Aurein1.2. Toxicity of AureinN2 for Hu02 cell lines was between 20 and 40% at the concentration of 8–500 μg/mL. In this study, we were able to improve antimicrobial activity of two synthetic derivatives of the Aurein family against Gram-negative bacteria by using machine-learning algorithm and other in silico methods.     

Synthesis and Antimicrobial Activity of Some Novel 2‐[4‐(Substituted Piperazin‐/Piperidin‐1‐ylcarbonyl)phenyl]‐1H‐benzimidazole Derivatives

In this study, we report the synthesis and antimicrobial evaluation of several new 4‐(1H‐benzimidazol‐2‐yl)benzamides ( 11 – 30 ) and 5‐chloro‐1‐(p‐fluorobenzyl)‐2‐{4‐[(4‐methylpiperazin‐1‐yl)carbonyl]phenyl}‐1H‐benzimidazole ( 33 ). Compound 20 exhibited the best antibacterial activity with MIC value of 6.25 μg/mL against Staphylococcus aureus and methicillin‐resistant Staphylococcus aureus (MRSA). Significant antifungal activities were obtained with the compounds 13 , 14, 18 , 19, and 33 with MIC values of 3.12 μg/mL which are close to fluconazole.     

Chemical composition and evaluation of modulatory of the antibiotic activity from extract and essential oil of Myracrodruon urundeuva

Context: The combination of antibiotics with natural products has demonstrated promising synergistic effects in several therapeutic studies.

Objective: The aim of this study was to determine the effect of a combination of an ethanol extract of Myracrodruon urundeuva Fr. All. (Anacardiaceae) (aroeira plant) and its essential oil with six antimicrobial drugs against multiresistant strains of Staphylococcus aureus and Escherichia coli from clinical isolates.

Materials and methods: After identification of the chemical components by GC-MS, the antibacterial activity of the natural products and antibiotics was assessed by determining the minimal inhibitory concentration (MIC) using the microdilution method and concentrations ranging 8–512?μg/mL and 0.0012–2.5?mg/mL, respectively. Assays were performed to test for a possible synergistic action between the plant products and the antimicrobials, using the extract and the oil at a sub-inhibitory concentration (128?μg/mL) and antibiotic at concentrations varying between 8 and 512?μg/mL.

Results: The GC-MS analysis identified the main compound as δ-carene (80.41%). The MIC of the natural products was >1024?μg/mL, except against S. aureus ATCC25923. Only the combinations of the natural products with gentamicin, amikacin and clindamycin were effective against S. aureus 358, enhancing the antibiotic activity by reducing the MIC.

Conclusions: The extract from aroeira showed a higher antibacterial activity and the oil was more effective in potentiating the activity of conventional antibiotics.     

Screening of in vitro antimicrobial activity of plants used in traditional Indonesian medicine

Context: In many regions of Indonesia, there are numerous traditional herbal preparations for treatment of infectious diseases. However, their antimicrobial potential has been poorly studied by modern laboratory methods.

Objective: This study investigates in vitro antimicrobial activity of 49 ethanol extracts from 37 plant species used in Indonesian traditional medicine for treatment against Candida albicans, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.

Materials and methods: The plants were collected from the Biopharmaca collection garden, Bogor, Indonesia. The plant material was dried, finely grounded, extracted using ethanol, concentrated, and the dried residue was dissolved in 100% DMSO. Antimicrobial activity was determined in terms of a minimum inhibitory concentration (MIC) using a broth microdilution method in 96-well microplates.

Results: The extract of Orthosiphon aristatus (Blume) Miq. (Lamiaceae) leaf produced the strongest antimicrobial effect, inhibiting the growth of C. albicans (MIC 128?μg/mL), S. aureus (MIC 256?μg/mL), E. faecalis (MIC 256?μg/mL) and P. aeruginosa (MIC 256?μg/mL). The leaf extract of Woodfordia floribunda Salisb. (Lythraceae) also exhibited significant effect against C. albicans (MIC 128?μg/mL), S. aureus (MIC 256?μg/mL) and E. faecalis (MIC 256?μg/mL). Rotheca serrata (L.) Steane &; Mabb. (Lamiaceae) leaf extract inhibited the growth of S. aureus (MIC 256 µg/mL) and C. albicans (MIC 256 µg/mL).

Discussion and conclusions: The leaf extract of O. aristatus and W. floribunda exhibited a significant anti-candidal effect. Therefore, both of these plants can serve as prospective source materials for the development of new anti-candidal agents.     

Antiplasmodial and antimicrobial activities of South African marine algal extracts

Seventy-eight crude organic fractions from nineteen species of marine algae collected from the coast of South Africa were screened for activity against a chloroquine sensitive strain of Plasmodium falciparum (D10), Staphylococcus aureus, Klebsiella pneumoniae, Mycobacterium aurum and Candida albicans. Fifteen crude fractions showed good antiplasmodical activity (IC₅₀?<10 μg/mL). The dichloromethane fraction from Sargassum heterophyllum (Turner) C. Agardh (Sargassaceae) was the most active with an IC₅₀ value of 2.8 μg/mL. Eleven extracts showed MIC values ≤?1?mg/mL against at least one of S. aureus, K. pneumoniae, M. aurum and C. albicans. The broadest spectrum of antimicrobial activity was exhibited by the aqueous-HP20 fraction of Polysiphonia incompta Harvey (Rhodomelaceae). This study shows that marine algae not only produce antimicrobial compounds but also may be a source of antimalarial lead compounds.     

Antimicrobial Properties of Brevinin‐2‐Related Peptide and its Analogs: Efficacy Against Multidrug‐Resistant Acinetobacter baumannii

Brevinin‐2 related peptide (B2RP; GIWDTIKSMG¹⁰KVFAGKILQN²⁰L.NH₂), first isolated from skin secretions of the mink frog Lithobates septentrionalis, shows broad‐spectrum antimicrobial activity but its therapeutic potential is limited by moderate hemolytic activity. The peptide adopts an α‐helical conformation in a membrane‐mimetic solvent but amphipathicity is low. Increasing amphipathicity together with hydrophobicity by the substitutions Lys¹⁶→Leu and Lys¹⁶→Ala increased hemolytic activity approximately fivefold without increasing antimicrobial potency. The substitution Leu¹⁸→Lys increased both cationicity and amphipathicity but produced decreases in both antimicrobial potency and hemolytic activity. In contrast, increasing cationicity of B2RP without changing amphipathicity by the substitution Asp⁴→Lys resulted in a fourfold increase in potency against Escherichia coli [minimal inhibitory concentration (MIC) = 6 μm ) and twofold increases in potency against Staphylococcus aureus (MIC = 12.5 μm ) and Candida albicans (MIC = 6 μm ) without changing significantly hemolytic activity against human erythrocytes (LC₅₀ = 95 μm ). The emergence of antibiotic‐resistant strains of the Gram‐negative bacterium Acinetobacter baumannii constitutes a serious risk to public health. B2RP (MIC = 3–6 μm ) and [Lys⁴]B2RP (MIC = 1.5–3 μm ) potently inhibited the growth of nosocomial isolates of multidrug‐resistant Acinetobacter baumannii. Although the analogs [Lys⁴, Lys¹⁸]B2RP and [Lys⁴, Ala¹⁶, Lys¹⁸]B2RP showed reduced potency against Staphylococcus aureus, they retained activity against Acinetobacter baumannii (MIC = 3–6 μm ) and had very low hemolytic activity (LC₅₀ > 200 μm ).     

Formulation Optimization of Chitosan-Stabilized Silver Nanoparticles Using In Vitro Antimicrobial Assay

Antimicrobial resistance at the infected site is a serious medical issue that increases patient morbidity and mortality. Silver has antibacterial activity associated with some dose-dependent toxicity. Silver nanoparticles, due to larger surface area, have antibacterial properties, which make them useful in the treatment of infections. Chitosan-stabilized silver nanoparticles (CH-AgNP) were formulated and evaluated for minimal inhibitory concentration and minimal bactericidal concentration testing against Staphylococcus aureus ATCC 29213, S aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, and 20 methicillin-resistant S aureus isolates. Minimum biofilm eradication concentration study was used to evaluate the biofilm reduction, and in vitro antimicrobial checkerboard assays were performed. The effective optimum ratio of AgNP:chitosan solution was 1:4. Minimal inhibitory concentration and minimal bactericidal concentration ranges of CH-AgNP were 4 to 14 times lower compared to AgNP alone against methicillin-resistant S aureus isolates. Minimum biofilm eradication concentration values of CH-AgNP for ATCC PA-01, P aeruginosa isolate 1, and P aeruginosa isolate 2 were found to be >84.59 μg/mL, 42.29 μg/mL, and 21.15 μg/mL, respectively. Thus, CH-AgNP is a potential formulation for wound treatment and management of infected sites associated with antimicrobial resistance.     

Antimicrobial activity of four annual Papaver species growing in Turkey

The extracts obtained from aerial parts of four annual Papaver (Papaveraceae) species from sections Argemonidium (P. argemone L. subsp. davisii Kadereit) and Rhoeadium (P. clavatum Boiss. & Hausskn. ex Boiss., P. dubium L. subsp. lecoqii var. lecoqii (Lamotte) Syme Kadereit and P. rhoeas L.) have been investigated for antimicrobial activity using a microbroth dilution technique. The antimicrobial activity of these species is reported for the first time. The petroleum ether and diethyl ether extracts of P. dubium subsp. lecoqii showed antibacterial activity against Staphylococcus aureus (MIC: 9.76 and 19.52 μg/mL, respectively). The diethyl ether and chloroform extracts of P. argemone subsp. davisii and diethyl ether, chloroform and acetone extracts of P. rhoeas had activity against S. aureus with a MIC value of 39.06 μg/mL.     

Synthesis and In Vitro Antibacterial Activity of 7‐(3‐Alkoxyimino‐4‐methyl‐4‐methylaminopiperidin‐1‐yl)‐fluoroquinolone Derivatives

A series of novel 7‐(3‐alkoxyimino‐4‐methyl‐4‐methylaminopiperidin‐1‐yl)fluoroquinolone derivatives were designed, synthesized, and characterized by ¹H‐NMR, MS, and HRMS. These fluoroquinolones were evaluated for their in‐vitro antibacterial activity against representative Gram‐positive and Gram‐negative strains. Generally, all of the target compounds have considerable antibacterial activity against the tested forty strains, and exhibit exceptional potency in inhibiting the growth of methicillin‐sensitive Staphylococcus aureus (MSSA) and methicillin‐resistant S. aureus (MRSA) ATCC33591 (MICs: 0.06 to 2 μg/mL). In particular, compounds 14 , 19 , 28 , and 29 are fourfold more potent than ciprofloxacin against MSSA 08‐49. Compounds 23 , 26 , and 27 are twofold more potent than ciprofloxacin against MRSA ATCC33591 and MSSA ATCC29213. In addition, compound 14 exhibits excellent activity (MIC: 0.06 μg/mL) against Acinetobactes calcoaceticus, which is two‐ to 16‐fold more potent than the reference drugs gemifloxacin, levofloxacin, and ciprofloxacin.     

Evaluation of the antibacterial activity of the methylene chloride extract of Miconia ligustroides,isolated triterpene acids,and ursolic acid derivatives

The methylene chloride extract of Miconia ligustroides (DC.) Naudin (Melastomataceae), the isolated compounds ursolic and oleanolic acids and a mixture of these acids, and ursolic acid derivatives were evaluated against the following microorganisms: Bacillus cereus (ATCC 14579), Vibrio cholerae (ATCC 9458), Salmonella choleraesuis (ATCC 10708), Klebsiella pneumoniae (ATCC 10031), and Streptococcus pneumoniae (ATCC 6305). The microdilution method was used for determination of the minimum inhibitory concentration (MIC) during evaluation of the antibacterial activity. The methylene chloride extract showed no activity against the selected microorganisms. Ursolic acid was active against B. cereus, showing a MIC value of 20?μg/mL. Oleanolic acid was effective against B. cereus and S. pneumoniae with a MIC of 80?μg/mL in both cases. The mixture of triterpenes, ursolic and oleanolic acids, did not enhance the antimicrobial activity. However, the acetyl and methyl ester derivatives, prepared from ursolic acid, increased the inhibitory activity for S. pneumoniae.     

Evaluation of antimicrobial properties of Achillea L. flower head extracts

Thirty-nine extracts obtained from flower heads of 13 Achillea species [A. multifida (DC.) Boiss., A teretifolia Waldst.&Kitt., A. schischkinii Sosn., A. setacea Waldst.&Kitt., A. crithmifolia Waldst.&Kitt., A. falcata L., A. biebersteinii Afan, A. coarctata Poir., A. millefolium L. subsp. pannonica (Scheele) Hayek., A. clypeolata Sm., A. kotschyi Boiss. subsp. kotschyi, A. phyrigia Boiss.&Bal,. and A. nobilis L. subsp. neilreichii (Kerner) Formánek] were evaluated for antimicrobial activity against Escherichia coli ATCC 29908, hemorrhagic E. coli (O157:H7) RSSK 232, E. coli ATCC 25922, Staphylococcus aureus ATCC 43300 (methicillin/oxacillin-resistant), S. aureus ATCC 6538/P, Streptococcus epidermidis ATCC 12228, Salmonella typhimurium CCM 5445, Bacillus cereus ATCC 7064, Bacillus subtilis ATCC 6633, Pseudomonas aeroginosa ATCC 27853, Enterococcus faecalis ATCC 29212, and Candida albicans ATCC 90028. The minimum inhibitory concentrations (MICs) were determined for all extracts against the tested organisms. Hexane extracts of A. coarctata and A. setacea showed antibacterial activity against E. faecalis (MIC=31.25 and 62.5 μg/mL, respectively). Chloroform extracts of a number of Achillea species showed selective activity against the tested bacteria isolates; MICs for the most active species (A. teretifolia, A. multifida) were found to range from 50 to 75 μg/mL against S. aureus, S. epidermidis, and S. typhymurium. All of the extracts were inactive against C. albicans at the tested concentrations. The study has shown that several Achillea species possess antibacterial activity, which may yield novel antibacterial compounds with potential use as phytotherapeutics.     

Efficient Synthesis and Biological Evaluation of a Novel Series of 1,5‐Benzodiazepine Derivatives as Potential Antimicrobial Agents

A series of novel 1,5‐benzodiazepine derivatives were rationally designed and synthesized following the principle of the superposition of bioactive substructures by the combination of 1,5‐benzodiazepine, pyridine (phenyl), and an ester group. The structures of the target compounds were determined by ¹H NMR, ¹³C NMR, MS, IR, and elemental analysis. All the synthesized compounds were evaluated for their antimicrobial activities in vitro against the fungi C. neoformans, C. neoformans clinical isolates (ATCC 32264), C. albicans (ATCC 10231), Gram‐negative bacterium E. coli (ATCC 44752), and Gram‐positive bacterium S. aureus (ATCC 25923). The results of the bioactive assay demonstrated that most of the tested compounds exhibited variable inhibitory effects on the growth of the tested microorganisms. All the active compounds showed better antifungal activity than antibacterial activity. Notably, compound 2b displayed the highest activity (MIC = 30 μg/mL) against C. neoformans and (MIC = 31 μg/mL) against C. neoformans clinical isolates. In addition, compound 2a also showed excellent activity against C. neoformans and C. neoformans clinical isolates with minimum inhibitory concentration of 35 and 36 μg/mL, respectively. Compounds 2a and 2b were further studied by evaluating their cytotoxicities, and the results showed that they have relatively low level cytotoxicity for BV2 and 293T cell. Preliminary structure‐activity relationship study on three diverse sets (C‐2, C‐3, and C‐8 positions) of 1,5‐benzodiazepines was performed. The results revealed that the presence of a ‐CH₃ group at the C‐8 position had a positive effect on the inhibitory activity of these compounds. Additionally, the 2‐pyridyl group at the C‐2 position may be a pharmacophore and ‐COOC₂H₅ at C‐3 position is the best substituent for the maintenance of antimicrobial activities.     

Design,synthesis, and biological evaluation of 1,8-naphthyridine glucosamine conjugates as antimicrobial agents

In the quest for discovering potent antimicrobial agents with lower toxicity, we envisioned the design and synthesis of nalidixic acid-D-(+)-glucosamine conjugates. The novel compounds were synthesized and evaluated for their in vitro antimicrobial activity against Gram positive bacteria, Gram negative bacteria and fungi. Cytotoxicity using MTT assay over L6 skeletal myoblast cell line, ATCC CRL-1458 was carried out. In vitro antimicrobial assay revealed that 1-ethyl-7-methyl-4-oxo-N-(1,3,4,6-tetra-O-acetyl-2-deoxy-D-glucopyranose-2-yl)-[1,8]-naphthyridine-3-carboxamide (5) and 1-ethyl-7-methyl-4-oxo-N-(2-deoxy-D-glucopyranose-2-yl)-[1,8]-naphthyridine-3-carboxamide (6) possess growth inhibitory activity against resistant Escherichia coli NCTC, 11954 (MIC 0.1589 mM) and Methicillin resistant Staphylococcus aureus ATCC, 33591 (MIC 0.1589 mM). Compound (5) was more active against Listeria monocytogenes ATCC 19115 (MIC 0.1113 mM) in comparison with the reference nalidixic acid (MIC 1.0765 mM). Interestingly, compound (6) had potential antifungal activity against Candida albicans ATCC 10231 (MIC <0.0099 mM). Remarkably, the tested compounds had low cytotoxic effect. This study indicated that glucosamine moiety inclusion into the chemical structure of the marketed nalidixic acid enhances antimicrobial activity and safety.     

Synthesis,antioxidant and antimicrobial evaluation of simple aromatic esters of ferulic acid

Aromatic ester derivatives of ferulic acid where the phenolic hydroxyl is free (6a–d) or acetylated (5a–d) were evaluated for their antioxidant and antimicrobial properties. The superoxide radical scavenging capacity of compounds 5d and 6d–e (IC₅₀ of 0.19, 0.27 and 0.20 mM, respectively) was found to be twice as active as α-tocopherol (IC₅₀ = 0.51 mM). DPPH radical scavenging capacity was moderate and only found in compounds bearing free phenolic hydroxyl groups (6a–e). With regard to antimicrobial properties, compounds 6b and 6c displayed significant activity against Enterococcus faecalis (MICs = 16 μg/mL) and vancomycin-resistant E. faecalis (MIC for 6b, 32 and for 6c, 16 μg/mL). Compound 6c also demonstrated prominent activity against planktonic Staphylococcus aureus with a MIC value of <8 μg/mL and it inhibited bacterial biofilm formation by S. aureus with a MBEC value of <8 μg/mL, which was 64 and 128 times more potent than ofloxacin and vancomycin, respectively.     

GC-MS analysis and antimicrobial activity of alkaloid extract from Genista vuralii

In the present study, the alkaloid composition of the aerial parts of Genista vuralii A. Duran & H. Dural (Fabaceae) was investigated by capillary GC-MS. Ten quinolizidine alkaloids were identified by capillary GC-MS, namely, N-methylcytisine, cytisine, tetrahydrorhombifoline, 17-oxosparteine, 5,6-dehydrolupanine, lupanine, 17-oxolupanine, anagyrine, baptifoline, and 13α-tigloyloxylupanine. Among them, anagyrine (93.04%) was the most abundant alkaloid. Furthermore, antibacterial and antifungal activities of the alkaloid extract of G. vuralii were tested against standard strains of bacteria (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus) as well as fungi (Candida albicans, Candida krusei). The alkaloid extract of G. vuralii presented good activity against S. aureus, B. subtilis, and C. krusei, with minimum inhibitory concentrations (MIC) of 62.5 μg/mL. The remaining MIC values were found to range between 125 and 500 μg/mL. To the best of our knowledge, the current work is the first to report the alkaloid profile and antimicrobial activity of G. vuralii L. growing in Turkey.     

Biofilm Eradication Kinetics of the Ultrashort Lipopeptide C12‐OOWW‐NH2 Utilizing a Modified MBEC Assay™

In this study, we report the antimicrobial planktonic and biofilm kill kinetics of ultrashort cationic lipopeptides previously demonstrated by our group to have a minimum biofilm eradication concentration (MBEC) in the microgram per mL (μg/mL) range against clinically relevant biofilm‐forming micro‐organisms. We compare the rate of kill for the most potent of these lipopeptides, dodecanoic (lauric) acid‐conjugated C₁₂‐Orn‐Orn‐Trp‐Trp‐NH₂ against the tetrapeptide amide H‐Orn‐Orn‐Trp‐Trp‐NH₂ motif and the amphibian peptide Maximin‐4 via a modification of the MBEC Assay^? for Physiology & Genetics (P&G). Improved antimicrobial activity is achieved upon N‐terminal lipidation of the tetrapeptide amide. Increased antimicrobial potency was demonstrated against both planktonic and biofilm forms of Gram‐positive micro‐organisms. We hypothesize rapid kill to be achieved by targeting of microbial membranes. Complete kill against established 24‐h Gram‐positive biofilms occurred within 4 h of exposure to C₁₂‐OOWW‐NH₂ at MBEC values [methicillin‐resistant Staphylococcus epidermidis (ATCC 35984): 15.63 μg/mL] close to the values for the planktonic minimum inhibitory concentration (MIC) [methicillin‐resistant Staphylococcus epidermidis (ATCC 35984): 1.95 μg/mL]. Such rapid kill, especially against sessile biofilm forms, is indicative of a reduction in the likelihood of resistant strains developing with the potential for quicker resolution of pathogenic infection. Ultrashort antimicrobial lipopeptides have high potential as antimicrobial therapy.     

Antimicrobial activity of the crude ethanol extract from Pimenta pseudocaryophyllus

The antimicrobial activity of the crude ethanol extract from Pimenta pseudocaryophyllus (Gomes) L. R. Landrum (Myrtaceae), collected at two locations in Brazil, was investigated. Leaf samples were collected in April 2005 and in September 2005, both in Brasília, DF, Brazil, and in July 2000 in São Gonçalo do Abaeté, MG, Brazil. They were dried, crushed and used to obtain three crude ethanol extracts. The agar diffusion test was used for antimicrobial activity screening and the agar dilution method for determining the minimal inhibitory concentration (MIC). In assay conditions, extracts I, II and III demonstrated antimicrobial activity against Gram-positive Staphylococcus aureus, Micrococcus luteus, M. roseus, Bacillus cereus, B. atrophaeus, and B. stearothermophilus (MIC 0.39062 to 12.5?mg/mL, MIC 0.78125 to 1.5625?mg/mL and MIC 0.39062 to 1.5625?mg/mL, respectively), against Gram-negative Pseudomonas aeruginosa (MIC 0.39062 to 3.125?mg/mL, MIC 1.5625?mg/mL and MIC 0.78125 to 1.5625?mg/mL, respectively), against clinical isolates of Pseudomonas stutzeri (MIC 0.39062 to 0.78125?mg/mL, MIC 0.78125 to 1.5625?mg/mL, MIC 0.78125 to 1.5625?mg/mL, respectively) and also against Candida albicans fungi (MIC 0.19531?mg/mL for the extracts I, II and III). This study showed that the antimicrobial activity of P. pseudocaryophyllus might be considered sufficient to encourage further studies to isolate and identify its active principles. Pharmacological and toxicological studies are also necessary, followed by studies regarding the culturing and managing processes of this vegetable.