Strong Antibacterial Activity Research Articles

Design and Fabrication of Broad-Spectrum Antimicrobial Porous Metallo-Polymeric Microsphere for Water Disinfection.

An expedient and efficient approach is used to synthesize a new class of metallo-polymeric microspheres (MPMs) as antimicrobials to succumb the wide range of bacteria from water. Three types of MPMs, that is, poly[Silver (I)-methacrylate-co-methylmethacrylate] (pAgMA), poly[Copper (II)-methacrylate-co-methyl methacrylate] (pCuMA), and poly[Nickel (II)-methacrylate-co-methylmethacrylate] (pNiMA), are prepared via radical suspension polymerization technique in 3D shape with porous texture. The structural and morphological characterization of the prepared microspheres are examined by analytical techniques. The antimicrobial potentialities of prepared MPMs are investigated at the laboratory scale study, revealing that the MPMs exhibit strong antibacterial activity (≈99.9% killing) against Gram-negative and Gram-positive bacteria [Enterobacter hormaechei (EH), Bacillus megatarium (BM), and Bacillus bataviensis (BB)]. The MacConkey agar medium test reveals that MPMs have substantial biocidal efficacy against broad-spectrum Gram-negative bacteria present in tap water. The MPMs exhibit significant antimicrobial efficacy via contact killing owe to the presence of integrated biocidal metal moiety, which represents that the MPMs are safe for water disinfection.

Study of andrographolide bioactivity against Pseudomonas aeruginosa based on computational methodology and biochemical analysis.

Andrographolide is one of the main biologically active molecules isolated from Andrographis paniculata (A. paniculata), which is a traditional Chinese herb used extensively throughout Eastern Asia, India, and China. Pseudomonas aeruginosa, often known as P. aeruginosa, is a common clinical opportunistic pathogen with remarkable adaptability to harsh settings and resistance to antibiotics. P. aeruginosa possesses a wide array of virulence traits, one of which is biofilm formation, which contributes to its pathogenicity. One of the main modulators of the P. aeruginosa-controlled intramembrane proteolysis pathway is AlgW, a membrane-bound periplasmic serine protease. In this work, we have used a set of density functional theory (DFT) calculations to understand the variety of chemical parameters in detail between andrographolide and levofloxacin, which show strong bactericidal activity against P. aeruginosa. Additionally, the stability and interaction of andrographolide and levofloxacin with the protein AlgW have been investigated by molecular docking and molecular dynamics (MD) simulations . Moreover, the growth and inhibition of biofilm production by P. aeruginosa experiments were also investigated, providing insight that andrographolide could be a potential natural product to inhibit P. aeruginosa.

Antimicrobial Activity of Grapefruit Seed Extract on Edible Mushrooms Contaminations: Efficacy in Preventing Pseudomonas spp. in Pleurotus eryngii.

Pleurotus eryngii is an edible mushroom that suffers significant losses due to fungal contamination and bacteriosis. The Pseudomonadaceae family represents one of the most frequent etiologic agents. Grapefruit seed extract (GSE) is a plant extract that contains different bioactive components, such as naringin, and exhibits a strong antibacterial and antioxidant activity. Over the last decade, GSE use as an alternative to chemical treatments in the food sector has been tested. However, to our knowledge, its application on mushroom crops has never been investigated. This study focuses on evaluating GSE efficacy in preventing P. eryngii yellowing. GSE antibiotic activity, inhibitory and bactericidal concentrations, and antibiofilm activity against several microorganisms were tested with the Kirby-Bauer disk diffusion assay, the broth microdilution susceptibility test, and the Crystal violet assay, respectively. In vitro, the extract exhibited antimicrobial and antibiofilm activity against Staphylococcus aureus 6538 and MRSA (wild type), Escherichia coli ATCC 8739, and Pseudomonas spp. (Pseudomonas aeruginosa 9027, P. fluorescens (wild type)). GSE application in vivo, in pre- and post-sprouting stages, effectively prevented bacterial infections and subsequent degradation in the mushroom crops: none of the P. eryngii treated manifested bacteriosis. Our findings support the use of GSE as an eco-friendly and sustainable alternative to chemical treatments for protecting P. eryngii crops from bacterial contamination, consequently ensuring food safety and preventing financial losses due to spoilage. Furthermore, GSE's potential health benefits due to its content in naringin and other bioactive components present new possibilities for its use as a nutraceutical in food fortification and supplementation.

Synergistic photogeneration of nitric oxide and singlet oxygen by nanofiber membranes via blue and/or red-light irradiation: Strong antibacterial action

New functionalities were added to biocompatible polycaprolactone nanofiber materials through the co-encapsulation of chlorin e6 trimethyl ester (Ce6) photogenerating singlet oxygen and absorbing light both in the blue and red regions, and using 4-(N-(aminopropyl)-3-(trifluoromethyl)-4-nitrobenzenamine)-7-nitrobenzofurazan, NO-photodonor (NOP), absorbing light in the blue region of visible light. Time-resolved and steady-state luminescence, as well as absorption spectroscopy, were used to monitor both photoactive compounds. The nanofiber material exhibited photogeneration of antibacterial species, specifically nitric oxide and singlet oxygen, upon visible light excitation. This process resulted in the efficient photodynamic inactivation of E. coli not only close to nanofiber material surfaces due to short-lived singlet oxygen, but even at longer distances due to diffusion of longer-lived nitric oxide. Interestingly, nitric oxide was also formed by processes involving photosensitization of Ce6 during irradiation by red light. This is promising for numerous applications, especially in the biomedical field, where strictly local photogeneration of NO and its therapeutic benefits can be applied using excitation in the “human body phototherapeutic window” (600–850 nm). Generally, due to the high permeability of red light, the photogeneration of NO can be achieved in any aqueous environment where direct excitation of NOP to its absorbance in the blue region is limited.

Design, synthesis and preliminary antibacterial evaluation of novel 1,3-benzoxazole/carboximidamide- and 1,3-benzoxazole/3-aryl-1,2,4-oxadiazole hybrids

Two series of 1,3-benzoxazole/carboximidamides 5a-i and 1,3-benzoxazole/3-aryl-1,2,4-oxadiazoles 6a-i were prepared from the reactions of (1,3-benzoxazol-2-ylthio)acetic acid (2) with the corresponding arylamidoximes 4a-i using excess N,N'-carbonyldiimidazole (CDI). The antibacterial studies revealed that hybrid 5a demonstrated exceptional activity against the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus, with inhibition zones measuring 34 mm and 36 mm, respectively. Moreover, hybrid 5a proved strong antibacterial activity against the against Gram-negative Klebsiella pneumoniae with inhibition zone equal to 32 mm. on the other hand, hybrid 5a displayed moderate activity against Gram-negative Escherichia coli, resulting in a 15 mm inhibition zone. Hybrid 6e (with 4-methoxyphenyl) was the most potent hybrid against B. subtilis, S. aureus and K. pneumoniae with inhibition zones equal to 32, 36 and 34 mm, respectively, followed by hybrids 6b (with 4-chlorophenyl) with inhibition zones equal to 31, 34 and 35 mm, respectively. Moreover, hybrid 5a exhibited strong antibacterial activity against B. subtilis, S. aureus and K. pneumoniae with minimum inhibitory concentration (MIC) values of 1.97, 0.97 and 3.90 μM, respectively, while hybrid 6b showed strong antibacterial activity with MIC values of 7.81, 3.90 and 3.90 μM, respectively, and hybrid 6e demonstrated antibacterial activity with MIC values of 3.90, 0.97 and 1.95 μM, respectively.

Fabrication and Therapeutic Process of a Green Silver-Nanoparticle-Embedded Mucilage Microsphere for Pathogenic-Bacteria-Infected Second-Degree Burn and Excision Wounds.

Multidrug-resistant bacteria are a serious problem in biomedical applications that decrease the wound healing process and increase the mortality rate. Therefore, in this study, we have prepared a green-synthesized silver-nanoparticle-encapsulated mucilage microsphere (HMMS@GSNP) from Hibiscus rosa sinensis leaves and applied it to pathogen-infected burn and excision wounds. Biophysical properties like size, polydispersity index, absorbance capacity, and drug release were measured by different techniques like field-emission scanning electron microscopy, dynamic light scattering, swelling ratio, etc. The strong antibacterial activity of a HMMS@GSNP microsphere was measured by minimum inhibitory concentration assay, minimum bactericidal concentration assay, and agar well diffusion methods. The HMMS@GSNP microsphere enhanced the cell viability, cell proliferation, migration, antioxidant, and antiinflammation activity compared to untreated GSNP and HMMS, as quantified by MTT assay, BrdU assay, scratch wound assay, reactive oxygen species scavenging assay, and Western blot analysis, respectively. In the in vivo experiment, we used a methicillin-resistant Staphylococcus aureus bacteria-infected, burn-and-excision-wound-created male BALB/c mice model. The HMMS@GSNP-treated burn-and-excision-wound-infected mice showed significant results compared to other groups (untreated, Silverex Ionic Gel, AgNO3, HMMS, and GSNP), and the mice tissues were utilized for bacteria count, immunoblot analysis, histological studies, and real-time polymerase chain reaction. Thus, the HMM@GSNP microsphere is an excellent therapeutic material that can be used as a topical agent for the management of chronic wound therapy.

Bioactivity of Endophytic Fungi Isolates from Syzygium malaccense Twigs

Searching for medicinal raw materials derived from the isolation of secondary metabolite compounds is still being carried out to cure a range of illnesses, including infections and degenerative diseases caused by bacteria and free radicals. This research used endophytic fungi extract from the twig of Syzygium malaccense. The diffusion method was used for antibacterial activity and 2,2-diphenyl-1-picrylhydrazyl (DPPH) was used for antioxidant activity. Chemical compound was identified by using NMR spectroscopic method. This research found 5 isolate of endophytic fungi from twig of S. malaccense (YR1 – YR5). Strong antibacterial and antioxidant activity were showed by YR5. Based on molecular identification, YR5 was Fusarium verticillioides. Pure compound prodeced by endophytic fungi F. verticilloides was naphthalene (3-methoxy-7 methylnaphthalene-1,6-diol). This finding can be used as a basis for drug development.

Atlas pistachio (Pistacia atlantica) unripe fruit extract as a source of phytochemicals with anti-tyrosinase, antioxidant, and antibacterial properties

The current need for biologically active substances that are sustainable, allegedly beneficial to health, and may be employed as ingredients in cosmetic products has encouraged numerous researchers. Pistacia atlantica is known to contain compounds that possess strong biological effects beneficial to health. The objective of this study was the quantification of the polyphenols in unripe Atlas pistachio (AP) fruit extract and the evaluation of hydro-methanolic extract and anthocyanins for their antioxidant, anti-tyrosinase, and antimicrobial effects. The results revealed that the yield of the hydro-methanolic extract was 22.15%, characterized by 75.12 mg GAE/g DM for total phenolics and strong content of hydrolysable tannins (400.16 mg GAE/g DM). 1,1-dimethyl-allyl caffeate, hydroxytyrosol, ellagic acid, rutin, and kaempferol-3-O-glucoside were the most abundant components quantified by HPLC-DAD. The tyrosinase enzyme was significantly inhibited by AP extract (EC50 = 0.70 mg/mL). For the antioxidant properties, the hydrolyzed anthocyanin extract exhibited the best action against reducing power and β-carotene, compared to anthocyanins crude extract and fruits. This extract showed its stronger antibacterial activity. In conclusion, unripe AP fruit is a promising source of diverse phytochemicals that can be applied in medicinal, nutraceutical, and cosmetic applications as antioxidants and antimicrobials.

Activated carbon impregnated with Ag(0) and Cu oxides for the removal of Escherichia coli, Giardia, and Cryptosporidium (oo)cysts from water

Granular activated carbon (GAC) impregnated with silver or copper was evaluated as a point-of-use water treatment to improve the microbiological quality of drinking water processed by low-cost, newly developed GAC filters. Experiments were carried out in a point-of-use water purifying system using packed-bed filters of GAC impregnated with various concentrations of Ag(0) or Cu oxides. The pore and surface properties were studied in terms of BET volumetric measurement with nitrogen adsorption (BET area of metal-impregnated GAC lies within the range of 602 ∼ 866 m²g−1, while the surface area of non-treated GAC is 870 m²g-1), X-ray diffraction (identifying the presence of metallic silver and copper oxide in the GAC structure) and Scanning Electron Microscopy (revealed the presence of metal compounds deposited on the GAC surface). The performance of filters with GAC (water treatment capacity of 4 L/g) was evaluated against microbiological contaminants in synthetic water so that the best loading concentration to remove microorganisms from test water could be determined. The removal efficiency against Escherichia coli was higher when the amount of metal impregnated on GAC increased. GAC impregnated with Ag(0) at 5.0 wt% had a strong antibacterial activity for the growth of Escherichia coli. Samples of GAC impregnated with Ag(0) at 1.0 wt% and Cu oxides at 0.5 wt% were more efficient in the removal of Giardia and Cryptosporidium (oo) cysts. The above evaluations showed that the proposed apparatus, based on a gravitational point-of-use filter with an adsorbent with metals has antibacterial properties and may be recommended to communities for household treatment of drinking water.

Antimicrobial activity, minimum inhibitory concentration and cytotoxicity of thiadiazol compound

Aim. This study aims to investigate the biological activity and cytotoxicity of the prepared thiadiazole derivative compound. Methods. A thiadiazol chemical, 4-[5-amino 1,3,4-thiadiazole-2-yl] phenol, was prepared by reacting 2.762 grams (0.01 moles) of 4-hydroxybenzoic acid with 1.822 grams (0.01 moles) of thiosemicarbazide. The prepared thiadiazole antimicrobial activity was tested at concentrations of 30, 50, 80, and 100 mg/mL against Escherichia coli, Pseudomonas, Bacillus cereus, and Staphylococcus epidermidis. Results. The thiadiazole chemical compound was prepared and tested against several bacterial species. The minimum inhibitory concentration (MIC) for Escherichia coli, Bacillus cereus, and Staphylococcus epidermidis was 0.8 mg/mL. Pseudomonas was unaffected by this substance. Investigations were made into the cytotoxicity activities. When the concentration was less than 0.01 mg/mL, it was discovered that the produced thiadiazol also had no impact on the red blood cell. Conclusion. The results revealed that the thiadiazole chemical compound had strong antibacterial activity against some of the pathogenic bacteria. This means that the chemical compound can be used as a narrow spectrum antibiotic.

Anti-microbial activity of Ocimum sanctum L. gel against black pigmented microbes.

Black pigmented gram negative anaerobes are associated with periodontal disease and tooth loss. Therefore, it is of interest to evaluate the antimicrobial activity of Ocimum Sanctum.L (Tulsi) gel against black pigmented anaerobes. Plaque samples were collected from the subject and kept in anaerobic broth for 4 hours of incubation at 37°C. 50µL concentration of Tulsi gel was added and kept in gas pack system for 3-5 days. Zone of inhibition was measured. Ocimum sanctum L. (Tulsi) exhibits strong antibacterial activity against Black Pigmented bacteroides at 1% and 2%.Tulasi gel was effective at higher concentrations, indicating the possibility of using it as an adjunct to standard periodontal treatment.

STANDARDISATION OF BIOACTIVE MATERIALS FROM CHROMULINA FREIBERGENSISAGAINST HUMAN PATHOGENS USING GC-MS ANALYSIS

In the preceding ten years, there has been a surge in the distribution of secondary metabolites and pharmacologically dynamic compounds from marine microalgae. Chromulinafreibergensis provided the antibacterial metabolites lessons for the current research .The current secondary metabolites study was chosen to focus on the green algal Chromulinafreibergensis. To see whether the properties of pH, temperature, and salinity on the development of microalgae aided in the growth of microalgae, they were tested. Antibacterial activity against Vibrio cholerae, Klebsiella pneumonia, Escherichia coli, Pseudomonas aeruginosa, Salmonella sp., Proteus sp., Streptococcus pyrogens, Staphylococcus aureus, Bacillus megaterium, and Bacillus subtilis was tested for in different solvent extracts of Chromulinafreibergensis.On the ninth day of incubation, when the medium was adjusted to a pH of 9.0 in 30 ppt of salinity at 250C, the uppermost cell growth was noticed. Of all the investigated solvents, the butanol + isopropanol (1:1) crude extract of Chromulinafreibergensis tested the highest zone of inhibition (13.4 mm) against Salmonella. . The presence of rare chemical substances like 3, 3, 5-Trimethylheptane (M.W. 142.2) and n-Hexadecane (M.W. 226.2) in the crude extract of Chromulinafreibergensis was discovered using GC-MS analysis.These results demonstrated the strong antibacterial activity of the Chromulinafreibergensis Butanol + Isopropanol (1:1) extract, demonstrating its enormous potential as a solvent for the extraction of bioactive chemicals from natural sources for biomedical and pharmaceutical applications.

Identification of Metabolites from Catharanthus roseus Leaves and Stem Extract, and In Vitro and In Silico Antibacterial Activity against Food Pathogens.

The plant produced powerful secondary metabolites and showed strong antibacterial activities against food-spoiling bacterial pathogens. The present study aimed to evaluate antibacterial activities and to identify metabolites from the leaves and stems of Catharanthus roseus using NMR spectroscopy. The major metabolites likely to be observed in aqueous extraction were 2,3-butanediol, quinic acids, vindoline, chlorogenic acids, vindolinine, secologanin, and quercetin in the leaf and stem of the Catharanthus roseus. The aqueous extracts from the leaves and stems of this plant have been observed to be most effective against food spoilage bacterial strains, followed by methanol and hexane. However, leaf extract was observed to be most significant in terms of the content and potency of metabolites. The minimum inhibitory concentration (20 µg/mL) and bactericidal concentrations (35 g/mL) of leaf extract were observed to be significant as compared to the ampicillin. Molecular docking showed that chlorogenic acid and vindolinine strongly interacted with the bacterial penicillin-binding protein. The docking energies of chlorogenic acid and vindolinine also indicated that these could be used as food preservatives. Therefore, the observed metabolite could be utilized as a potent antibacterial compound for food preservation or to treat their illness, and further research is needed to perform.

An adaptive drug-releasing contact lens for personalized treatment of ocular infections and injuries

This research introduces an innovative solution to address the challenges of bacterial keratitis and alkali burns. Current treatments for bacterial keratitis and alkali burns rely on the frequent use of antibiotics and anti-inflammatory eye drops. However, these approaches suffer from poor bioavailability and fluctuating concentrations, leading to limited efficacy and potential drug resistance. Our approach presents an adaptive drug-releasing contact lens responsive to reactive oxygen species (ROS) at ocular inflammation sites, synchronously releasing Levofloxacin and Diclofenac. During storage, minimal drug release occurred, but over 7 days of wear, the lens maintained a continuous, customizable drug release rate based on disease severity. This contact lens had strong antibacterial activity and biofilm prevention, effectively treating bacterial keratitis. When combined with autologous serum, this hydrophilic, flexible lens aids corneal epithelial regeneration, reducing irritation and promoting healing. In summary, this ROS-responsive drug-releasing contact lens combines antibacterial and anti-inflammatory effects, offering a promising solution for bacterial keratitis and alkali burns.

Multifunctional embelin- poly (3-hydroxybutyric acid) and sodium alginate-based core-shell electrospun nanofibrous mat for wound healing applications

In this study, coaxial electrospinning is employed to make core-shell fibers, which represents a major advance in biomaterial innovation. Fibers that combine a protective shell and a therapeutic agent-loaded core, herald a revolutionary era in tissue engineering and wound care. Besides supporting cell growth, these fibers also preserve sterility, which makes them ideal for advanced wound dressings. We used embelin as the basis for this study because of its natural antibacterial properties. Its effectiveness in inhibiting the growth of bacteria made it the ideal candidate for our research. We have synthesized core-shell nanofibers that contain Sodium Alginate (SAL) in a Poly (ethylene oxide) (PEO) shell and Embelin in a Poly (3-hydroxybutyric acid) (PHB) core, which exhibit the homogeneity and flawless structure required for biomedical applications. When using SAL-PEO and EMB-PHB solutions dissolved in 1,1,1,3,3,3 hexafluoro-2-propanol (HFIP), high consistency in results can be achieved. A biocompatibility study was conducted using NIH-3T3 fibroblasts, which demonstrated remarkable adhesion and proliferation, with over 95 % growth supporting both PHB + SAL-PEO and EMB-PHB + SAL-PEO fibers. In addition, the scaffold loaded with Embelin shows strong antibacterial activity and cytocompatibility. The combined activity demonstrates the potential of EMB-PHB + SAL-PEO fibers in wound healing, where tissue regeneration and preservation of sterility are crucial. The optimized concentration of Embelin within these scaffolds demonstrates robust antibacterial efficacy while exhibiting minimal toxicity, thus positioning them as highly promising candidates for a wide range of biological applications, including wound healing.

Unique Azolyl Acylhydrazonyl Hybridization of Aloe Emodins to Access Potential Antibacterial Agents

Comprehensive SummaryA type of unique azole‐hybridized acylhydrazonyl aloe emodins (AAEs) were developed as new antibacterial agents for combating bacterial infections. Some target AAEs showed strong antibacterial activities, especially, tetrazolylthioether AAE 27a exhibited broad antibacterial spectrum with 16—256 folds and 8—64 folds more active antibacterial efficacy than the reference drugs aloe emodin and norfloxacin, respectively. Tetrazolylthioether AAE 27a also gave low hemolysis and cytotoxicity, as well as favorable bioavailability. Preliminary mechanism explorations revealed that tetrazolylthioether AAE 27a could cause bacterial membrane depolarization and damage the cell membrane, resulting in nucleic acid leakage. Moreover, compound 27a could intercalate into DNA to impede its replication and form supramolecular 27a‐DNA gyrase complex to disturb the function of DNA gyrase. These findings would provide valuable insights for the further exploration of azolyl acylhydrazonyl aloe emodins as new potential antibacterial candidates.

Optimization of Culture Conditions and Batch Process Control for the Augmented Production of Bacteriocin by Bacillus Species.

The emergence of antibiotic-resistant microorganisms poses a significant threat to human health worldwide. Recent advances have led to the discovery of molecules with potent antimicrobial activity from environmental sources. In this study, fifteen bacterial isolates were obtained from agricultural and polluted soil samples collected from different areas of the cities of Jizan and Jeddah. These isolates were screened for antagonistic activity against a set of human pathogenic bacterial strains. The results showed that two Bacillus strains, identified as Bacillus atrophaeus and Bacillus amyloliquefaciens based on 16S rDNA, synthesized bacteriocin with strong antibacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA) ATCC 33591, Pseudomonas aeruginosa ATCC 9027, Salmonella typhimum ATCC 14028, carbapenem-resistant E. coli, and MRSA 2. To optimize bacteriocin production, the effects of medium composition, incubation period, temperature, and pH were investigated. Nutrient broth and Mueller-Hinton broth were chosen as the optimal original media for bacteriocin production. The optimal incubation period, temperature, and pH were found to be 48 h at 37 °C and 7 pH in Bacillus atrophaeus and 72 h at 37 °C and 8 pH in Bacillus amyloliquefaciens. Batch cultures of Bacillus atrophaeus and Bacillus amyloliquefaciens were grown in a 10 L benchtop bioreactor, and pH control was found to significantly increase the production of bacteriocin by two-fold compared to uncontrolled conditions. The time course of growth, substrate consumption, pH, and enzyme production were investigated. This study demonstrates the potential of optimizing culture conditions and batch process control to enhance bacteriocin production by Bacillus spp.

Nisin—A Promising Antimicrobial Compound from Lactic Acid Bacteria

Nisin is a classical bacteriocin consisting of thirty-four amino acid residues and undergoing a high degree of post-translational modification to form a unique pentacyclic structure. Nisin is mainly synthesised by lactic acid bacteria. Under natural conditions, it exhibits strong antibacterial activity against Gram-positive organisms and, when combined with chelating agents, is effective against Gram-negative organisms. An excellent safety profile, low cytotoxicity and slow development of resistance are additional benefits. Currently, the application of nisin is focused on food preservation. This is due to the fact that nisin is naturally present in a wide range of historical fermented foods and its safety is fully guaranteed. With the continuous development of bacterial drug resistance and the consequent demand for new anti-infective drugs, its biomedical applications are being actively explored. However, due to the problems of drug stability, safety, and in vivo activity, there is still a certain distance from clinical application. In this paper, the author summarized the structure, biosynthetic mechanism, applications, and possible research directions of nisin.

Antibacterial activity of essential oils from Eucalyptus camaldulensis Dehn. and Eucalyptus tetragona F.Muell

IntroductionEucalyptus plants are used as a source of essential oils in Ethiopia and are traditionally used for the treatment of the common cold, stomachache, swelling and wounds. This study aims to determine the chemical composition and antibacterial activity of the essential oils of E. camaldulensis Dehn. and E. tetragona Muell. MethodologyThe chemical composition of the essential oils of E. camaldulensis Dehn. and E. tetragona F.Muell. was determined using gas chromatographymass spectrometry (GCMS), and their antibacterial activity of was evaluated against E. coli ATCC 25922 and S. ATCC 25923. ResultsThe yield of essential oil from the leaves of E. camaldulensis was 0.72% w/w, and the yield of essential oil from the leaves of E. tetragona was 0.80% w/w on the basis of fresh leaf weight. A total of 17 and 14 components were identified in E. camaldulensis and E. tetragona, respectively. The main components identified were 1,8-cineole, β-cymene and α–pinene in both Eucalyptus species analysed. The extracted essential oils displayed moderate to strong antibacterial activity. E. tetragona inhibited S. aureus at a lower concentration (0.625 μg/ml), while E. coli was less sensitive to the EOs of E. camaldulensis, with an MIC of 2.5 μg/ml. ConclusionThe essential oils of E. camaldulensis and E. tetragona exhibited significant antibacterial activity against E. coli and S. aureus. The results showed that the essential oils of E. camaldulensis and E. tetragona may be useful for treating various infectious diseases. Essential oils, particularly 1,8-cineole, can be used as alternative natural antimicrobial agents in the pharmaceutical and food industries.

Biosynthesis, characterization and study of the application of silver nanoparticle for 4-nitrophenol reduction, and antimicrobial activities

Silver nanoparticles (AgNPs) were synthesized from Vigna unguiculata (L) Walp extracted leaves, and characterized. The UV–Visible spectrum showed a peak between 411 and 415 nm at the Plasmon absorbance of the AgNPs. TEM showed that the size of AgNPs ranged from 5 to 13 nm. It was spherical with an average size of 11.08 nm. The size of AgNPs was 7 ± 6 nm and disperse in water. The AgNPs effectively reduced 4-Nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4. The AgNPs exhibited a strong antioxidant and antibacterial activity against Gram-negative bacteria: Escherichia coli (E. coli) and Klebsiella pneumonia and Gram-positive: Bacillus pumilus and Staphylococcus aureus. The average zones of inhibition of AgNPs were: 29 mm for Staphylococcus aureus, 23 mm for Bacillus pumilus, 17 mm for Klebsiella pneumonia and 15 mm for Escherichia coli (E. coli). Thus, AgNPs has exhibted good antibacterial activity compared to antibiotics drug and 4-NP reduction.