Ahmed Abdel-Megeed

Evaluation of extracts and essential oil from Callistemon viminalis leaves: Antibacterial and antioxidant activities, total phenolic and flavonoid contents

OBJECTIVE To investigate antioxidant and antibacterial activities of Callistemon viminalis (C. viminalis) leaves. METHODS The essential oil of C. viminalis leaves obtained by hydro-distillation was analyzed by GC/MS. Different extracts were tested for total phenolic and flavonoid contents and in vitro antioxidant (DPPH assay) and antibacterial (agar disc diffusion and 96-well micro-plates methods) actives. RESULTS Fourteen components were identified in the essential oil, representing 98.94% of the total oil. The major components were 1,8-cineole (64.53%) and α-pinene (9.69%). Leaf essential oil exhibited the highest antioxidant activity of (88.60±1.51)% comparable to gallic acid, a standard compound [(80.00±2.12)%]. Additionally, the biggest zone of inhibitions against the studied bacterial strains was observed by the essential oil when compared to the standard antibiotic (tetracycline). The crude methanol extract and ethyl acetate fraction had a significant antibacterial activity against the tested bacterial strains. CONCLUSIONS It can be suggested that C. viminalis is a great potential source of antibacterial and antioxidant compounds useful for new antimicrobial drugs from the natural basis. The present study revealed that the essential oil as well as the methanol extracts and ethyl acetate fraction of C. viminalis leaves exhibited highly significant antibacterial activity against the tested bacterial strains.

Nanospider technology for the production of nylon-6 nanofibers for biomedical applications

Nylon-6 nanofiber mat incorporated with 5,5-dimethyl hydantoin (DMH) as an antimicrobial drug was electrospun from formic acid. The morphology of the nanofiber mat using scanning electron microscope (SEM) showed that the obtained fiber had an average diameter of around 15-328 nm. The nanofiber was characterized by FTIR spectra, TGA, and DSC. The nanofiber containing drug showed initial fast release. It released about 55% of its drug content within the first two hours. Moreover, the antimicrobial activity of the electrospun nylon-6 nanofiber containing drug was examined against Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, and Aspergillus flavus. The nylon-6 nanofiber exhibited high inhibitory effects against the microbes. The results clearly indicate that the antimicrobial activity of the electrospun nylon-6 nanofiber containing drug varies with the species of the organisms used. Thus, the study ascertains the value of the use of electrospun nanofiber, which could be of considerable interest to the development of new antimicrobial materials. The microbes, examined by SEM, were totally deformed and exhibited severe destruction. Abnormal cell division was observed at high frequencies among cells that tried to divide in the presence of the nanofiber. Many cells were enlarged, elongated, empty ghosts, or fragmented, consistent with the extremely low viability.

Target and non-target toxicity of botanical insecticide derived from Couroupita guianensis L. flower against generalist herbivore, Spodoptera litura Fab. and an earthworm, Eisenia foetida Savigny

Botanical insecticides may provide alternatives to synthetic insecticides for controlling Spodoptera litura (F.) and they are target specific, biodegradable, and harmless to mammals. Eight natural chemical compounds with larvicidal activity were identified from fraction F6 of C. guianensis flower extract. Probit analysis of 95% confidence level exposed an LC50 of 223ppm against S. litura third instar larvae. The growth and development of S. litura was affected in sub-lethal concentrations of fraction F6 (50, 100, 150 and 200ppm) compared to controls. Similarly nutritional indices values decreased significantly compared to controls. Fraction F6 also damaged the gut epithelial layer and brush border membrane (BBM). This study also resolved the effects of toxicity to non-target earthworm treated with fraction F6 and chemical pesticides (monotrophos and cypermethrin) and the results showed that fraction F6 had no harmful effect on E. fetida. Further, fraction F6 was eluted and sub fractions F6c (50ppm) showed high mortality against S. litura third instar larvae. Octacosane from fraction F6c was established and confirmed using IR spectrum and HPLC. The time of retention of fraction F6c was confirmed with the octacosane standard. Fraction F6 of C. guianensis extract caused dose-dependent mortality towards S. litura. Octacosane in fraction F6c was establish to be the prominent chemical compound associated with causing mortality but other compounds present in the fraction F6 were shown to be associated with changes in development of S. litura at low dosages. S. litura at low dosage. Therefore, these findings suggest that octacosane may be one of the major insecticidal compounds affecting S. litura survival.

Synthesis and antibacterial of carboxymethyl starch-grafted poly(vinyl imidazole) against some plant pathogens

Poly(N-vinyl imidazole) (PVI) has been grafted onto carboxymethyl starch (CMS) in aqueous solution using potassium persulfate (KPS) as initiator. Reaction parameters that affect grafting efficiency and percentage grafting such as monomer and initiator concentration, the reaction temperature and time were investigated. The grafted products were characterized by FTIR, thermal analysis, SEM photograph and elemental analysis. The antibacterial effects of the carboxymethyl starch-grafted-poly(N-vinylimidazole) (CMS-g-PVI) was examined against two plant pathogens Gram negative bacteria: Xanthomonas perforanss and Xanthomonas oryzae. Generally, upon application of the CMS-g-PVI to the bacterial cells; the mortality rate increased from 45.71 to 59.37% for Xanthomonas perforans and X. oryzae, respectively. While the MIC for most of both bacterial strains were recorded at concentration of 60 μg/mL. The results indicate that CMS-g-PVI has bactericidal properties and can be used for seed treatment to control xanthomonads associated with bacterial leaf spot (BLS).

Fabrication of electrospun antimicrobial nanofibers containing metronidazole using nanospider technology

Nanospider technology as a modified electrospinning technique was used for the fabrication of electrospun nanofibers based on poly(vinyl alcohol) (PVA)/poly(ethylene oxide) (PEO) blend as drug delivery system (DDS) for metronidazole (MTZ) as an antimicrobial drug. Electrospun PVA/PEO/MTZ composite nanofibers were stabilized against disintegration in water by heating in oven at 110°C, or by soaking in isopropyl alcohol for 6 hrs. Incorporation of MTZ into electrospun nanofibers was confirmed by SEM, FT-IR spectra and TGA. The drug release results showed that the burst release was suppressed with stabilized electrospun nanofibers compared with non-stabilized ones. Electrospun PVA/PEO/MTZ composite nanofibers exhibited remarkable antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, Penicillium notatum and Aspergillus flavus which varies with the species of the tested organisms.

Anti-dengue efficacy of bioactive andrographolide from Andrographis paniculata (Lamiales: Acanthaceae) against the primary dengue vector Aedes aegypti (Diptera: Culicidae)

The current study investigated the toxic effect of the leaf extract compound andrographolide from Andrographis paniculata (Burm.f) against the dengue vector Ae. aegypti. GC-MS analysis revealed that andrographolide was recognized as the major chemical constituent with the prominent peak area compared with other compounds. All isolated toxic compounds were purified and confirmed through RP-HPLC against chemical standards. The larvicidal assays established at 25ppm of bioactive compound against the treated instars of Ae. Aegypti showed prominent mortality compared to other treated concentrations. The percent mortality of larvae was directly proportional to concentration. The lethal concentration (LC50) was observed at 12ppm treatment concentration. The bioactive andrographolide considerably reduced the detoxifying enzyme regulations of α- and β- carboxylesterases. In contrast, the levels of GST and CYP450 significantly increase in a dose dependent manner. The andrographolide also showed strong oviposition deterrence effects at the sub-lethal dose of 12ppm. Similarly, the mean number of eggs were also significantly reduced in a dose dependent manner. At the concentration of 12ppm the effective percentage of repellency was greater than 90% with a protection time of 15-210min, compared with control. The histopathology study displayed that larvae treated with bioactive andrographolide had cytopathic effects in the midgut epithelium compared with the control. The present study established that bioactive andrographolide served as a potential useful for dengue vector management.

k-Carrageenan/poly vinyl pyrollidone/polyethylene glycol/silver nanoparticles film for biomedical application

Biopolymer composite film containing k-carrageenan (KC), polyvinyl pyrrolidone (PVP), and polyethylene glycol (PEG) was formulated by dissolving KC and PVP in water containing PEG. Silver nanoparticles (AgNPs), was produced by Honeybee and added to solution. Finally, all solutions were poured onto dishes and dried overnight at 40°C to form the final films. Tensile strength (TS) and elongation (E %) is evaluated. The water contact angle is inspected. Thermal properties (TGA) and swelling behavior for water were considered. Fungal activity is also examined. Morphology of all films was also explored using scanning electron microscope. AgNPs induced significant hydrophilicity to KC-PVP-PEG film with contact angle of 41.6 and 34.7 for KC-PVP-PEG-AgNPs. Films with AgNPs exhibited higher thermal stability and strength properties than other films without. Films with AgNPs explore lower swelling behavior than other films without. Both SEM and EDX proved the deposition of AgNPs on the surface of films. Films with AgNPs showed higher activity against pathogenic fungi compared with the chemical fungicide; fluconazole.

Preparation of nylon-6/chitosan composites by nanospider technology and their use as candidate for antibacterial agents

Electrospun nylon-6/chitosan (nylon-6/Ch) nanofibers were prepared by nanospider technology. Quaternary ammonium salts as antibacterial agent were immobilized onto electrospun nylon-6/Ch nanofibers via surface modification by soaking the mat in aqueous solution of glycidyltrimethylammonium chloride (GTMAC) at room temperature overnight to give nylon-6/N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (nylon-6/HTCC). The morphological, structural and thermal properties of the nylon-6/ch nanofibers were studied by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). Biological screening has demonstrated the antibacterial activity of the electrospun nanofibers against Gram negative bacteria, Escherichia coli 35218, and Pseudomonas aeruginosa and Gram positive bacteria, Staphylococcus aureus 24213 among the tested microbes. Thus, the study ascertains the value of the use of electrospun nanofibers, which could be of considerable interest to the development of new antibacterial materials for biomedical applications.

OxymaPure/DIC: An Efficient Reagent for the Synthesis of a Novel Series of 4-[2-(2-Acetylaminophenyl)-2-oxo-acetylamino] Benzoyl Amino Acid Ester Derivatives

OxymaPure (ethyl 2-cyano-2-(hydroxyimino)acetate) was tested as an additive for use in the carbodiimide (DIC) approach for the synthesis of a novel series of α-ketoamide derivatives (4-[2-(2-acetylaminophenyl)-2-oxo-acetylamino]benzoyl amino acid ester derivatives). OxymaPure showed clear superiority to HOBt/DIC or carbodiimide alone in terms of purity and yield. The title compounds were synthesized via the ring opening of N-acylisatin. First, N-acetylisatin was reacted with 4-aminobenzoic acid under conventional heating as well as microwave irradiation to afford 4-(2-(2-acetamidophenyl)-2-oxoacetamido)benzoic acid. This α-ketoamide was coupled to different amino acid esters using OxymaPure/DIC as a coupling reagent to afford 4-[2-(2-acetylaminophenyl)-2-oxo-acetylamino]benzoyl amino acid ester derivatives in excellent yield and purity. The synthesized compounds were characterized using FT-IR, NMR, and elemental analysis.

Synthesis of Quaternized Amine-Terminated Polyacrylonitrile and Their Antimicrobial Assessment

Antimicrobial polymers based on polyacrylonitrile (PAN) have been prepared. The cyano groups of the polyacrylonitrile were modified through the reaction with different aliphatic diamines having varied chain lengths. Formation of biocidal polymers (antifungal and antibacterial agents) containing quaternary ammonium salts were then achieved by immobilization of glycidyl trimethyl ammonium chloride (GTMAC) onto the amine-terminated polymers. Antimicrobial activity of the prepared polymers was demonstrated against some selected plant and human pathogenic Gram-negative and Gram-positive bacteria, as well as some pathogenic fungi by the cut plug method and viable cell counting methods. Generally, all polymers showed an increase in the inhibitory action against all the tested microorganisms in comparison with their control.