No description available.

Combretaceae contain several species with bioactive properties - especially the genera Combretum and Terminalia. Pteleopsis myrtifolia and Quisqualis littorea belong to this family and have not previously been thoroughly investigated for their bioactivity. Leaf and fruit extracts of P. myrtifolia and leaf extracts of Q. littorea were separated by three different thin layer chromatography eluent systems. For all leaf and fruit material, the largest amount of acetone soluble material was extracted with extractants of intermediate polarity. Antibacterial activity of 30 extracts was investigated using a microplate serial dilution method and bioautography. The four most important nosocomial pathogens that are used worldwide namely two Gram-positive: Staphylococcus aureus and Enterococcus faecalis, and two Gram-negative bacteria: Pseudomonas aeruginosa and Escherichia coli were used as test organisms. Areas of growth inhibition were best defined after an eluent system that separates compounds of intermediate polarity had been used. The Gram-positive bacteria were most sensitive to some extracts of P. myrtifolia leaves. Fruit extracts exhibited minimum inhibitory concentrations (MIC) values as low as 0.04 mg/ml, less than that of the allopathic antibiotics, ampicillin and chloramphenicol. Q.littorea leaf extracts had an average MIC value of 0.32 mg/ml for Gram-negative bacteria. The average antibacterial activity expressed as total activity for each bacterium was higher in the leaves than in the fruit of P. myrtifolia. After considering the amount of antibacterial compounds extracted, toxicity of extractants to test organisms and miscibility of several extractants, acetone was eventually chosen as the best extractant for future extractions. Results obtained in this investigation showed clearly that P. myrtifolia leaves, fruit, and Q. littorea leaves contain several antibacterial compounds. Five different extracts of P. myrtifolia leaves were tested for growth inhibitory effects on different human cell lines (MCF-12, MCF-7, H157, WHCO3, HeLa). The non-cancerous MCF-12A cell line’s growth was not inhibited extensively, and the cancer cell lines - MCF-7, H157, WHCO3 and HeLa, differed in their sensitivity to the plant extracts. This indicated that the plant extracts’ effects were selective and not due to general toxicity. The effect of some extracts on certain cell lines, especially WHCO3, was growth inhibitory but not lethal. This is the desired effect – to inhibit growth of cancer cells, but not to be toxic to cells in general. The presence of tannin in extracts either promoted or inhibited growth inhibition of different cell lines. The same extractants that were used for cytotoxic tests were investigated for their antioxidant activity. All extracts gave positive scavenging capacity with the 1,2-diphenyl-2-picrylhydrazyl assay. The cold water, methanol and hot water extracts had vitamin C equivalents of 0.34, 0.20 and 0.147 mg/g respectively, all more than that of black tea. The solvent-solvent separation of P. myrtifolia leaves was started with acetone as an initial extractant. Separation was undertaken with immiscible solvents of different polarities. All fractions had antibacterial activity against the Gram-positive bacteria. The chloroform fraction was antibacterial to all bacteria tested, and had the largest amount of antibacterial compounds. Pure compounds were isolated from the chloroform fraction by column chromatography. One pure compound’s structure was elucidated as a pentacyclic triterpenoid, taraxerol (C30H50O). Taraxerol had MIC values of 0.04, 0.016, 0.63 and 0.31 mg/ml for the bacteria S. aureus, E. faecalis, P. aeruginosa and E. coli respectively. It significantly inhibited growth of the human lung cancer cell line H157 and did not display free radical scavenger activity. This is the first report of the antibacterial activity of several extracts from P. myrtifolia and Q. littorea, growth inhibition effects of several P. myrtifolia leaf extracts on the human cell lines MCF-12, MCF-7, H157 and WHCO3, the isolation of taraxerol from P. myrtifolia leaves, taraxerol’s antibacterial activity for above-mentioned test organisms, and growth inhibition effects on human cancer cell lines MCF-7, H157, WHCO3 and HeLa. / Thesis (PhD (Pharmacology))--University of Pretoria, 2008. / Pharmacology / unrestricted

The research activity described in the present thesis is devoted to the design and development of porous bioactive ceramic scaffolds addressed to the regeneration of bone tissue and was mainly carried out at the Institute of Science and Technology for Ceramics, belonging to the National Research Council of Italy (ISTEC-CNR), during my Ph.D. in Civil, Environmental and Mechanical Engineering (Curriculum B: Mechanics, Materials, Chemistry and Energy). The regeneration of critical size bone defects is still an unmet clinical need and since decades the development of bioactive scaffolds, capable to instruct and guide bone cells to tissue regeneration is a major research area in material science, including interdisciplinary approaches spanning from the field of chemistry, engineering, biology and medicine. In fact, the currently used bio-inert devices (e.g. metallic devices) can merely provide a mechanical support without regenerating the damaged bone tissue and often inducing adverse side effects such as infections while forcing the patient to frequent revision surgeries, with relevant socio-economic impact. The main aim of my work was the design and optimization of new materials and processes to produce bioactive ceramics implants as potential solution for the treatment of large and load-bearing bone defects, particularly suitable for cranio-maxillofacial, orthopaedic and spinal surgery. In my activity I synthesized new hydroxyapatite-based materials, Ca10(PO4)6(OH)2, exhibiting ionic substitutions designed to mimic the inorganic part of bone, particularly magnesium, strontium, zinc and carbonate, which increase the osteogenic ability and the bio-resorbability, promote the physiological bone turnover, thus suitable also for osteoporotic patients, as well as the antibacterial ability. After a general introduction of bone tissue physiology and an overview on the analytical methods involved in the research (Chapter I and Chapter II, respectively), my thesis focuses on the development of various hydroxyapatite nanophases showing multiple ionic substitutions including strontium or zinc ions, in association with magnesium and carbonate, with the purpose to provide synergistic biological effects such as osteogenic and antibacterial ability, and induce microstructural changes potentially improving the mechanical performance (Chapter III). In this Chapter, an important role was played by sintering, that was investigated varying different parameters like temperature and atmosphere (Air, CO2). The influence of doping ions and conditions of sintering was evaluated by chemical-physical, biological and mechanical characterization in order to understand how the presence of doping ions and different conditions of sintering influence the osteogenic properties and the mechanical behavior of the hydroxyapatite scaffolds. Then, Chapter IV describes novel nanocrystalline, multi-doped hydroxyapatite phases with excellent osteoinductive character and anti-infective properties, evaluated in collaboration with University of Pavia. Physico-chemical analysis highlighted the role of the surface state and charge, as induced by the ion doping, in the enhancement of the biological features. Finally, Chapter V describes the preparation of 3-D devices endowed where the porosity could be controlled and tailored to achieve suitable compromise between mechanical properties and porosity extent, relevant for bone invasion and osteointegration. The devices are obtained via direct foaming of multi-doped hydroxyapatite ceramic suspension with high-energy planetary ball milling. This method enabled the development of large and complex shape porous scaffolds, recapitulating composition, porosity and structure of the natural bone, thus promising for future practical applications in bone surgery. A better understanding of how dopant ions affect the mechanical properties of these scaffolds has been made possible thanks to the several mechanical and microstructural tests performed on them.

Contact-active antibacterial surfaces with irreversibly attached antibacterial com-pounds are a sustainable alternative to traditional biocides. No chemicals are released into nature and the antibacterial mechanism reduces the risk of the evolution of re-sistant bacteria. However, the preparation of such surfaces is far from sustainable, as organic solvents and harsh reaction conditions commonly are required. An alter-native option is to use polyelectrolyte multilayers (PEM), based on physical ad-sorption, which can be performed in water-based solutions at room temperature. Although contact-active antibacterial PEMs have been reported previously, this is the first study of renewable cellulosic wood fibres. The build-up of cationic polymer polyvinylamine (PVAm) and anionic polyacrylic acid (PAA) multilayers on model surfaces was studied to optimise adsorption. The amount of adsorbed polyelectrolytes was continuously growing with increasing number of layers, but remained dense and flat as the number of layers increased. The largest adsorption was obtained at a high salt concentration, which shielded the repulsion between the polymers. Model surfaces were also used to evaluate the influence of the polymer and number of layers on the antibacterial properties. Multilayers on model surfaces showed a low bacteriostatic effect, with up to approximately 40 % inhibition for 3 layers of un-modified PVAm/PAA. In contrast, when the same multilayers were applied on cel-lulosic fibres, bacterial-growth inhibition of > 99.9% was obtained. Hydrophobically modified PVAm did not yield better results, despite being superior in solution. An increase in fibre charge by fibre oxidation led to the largest amount of adsorbed pol-ymer and the best antibacterial properties, an effect that lasted for weeks. Electron microscopy study of bacteria on the fibres showed that the bacteria interacted more on a highly charged surface and that the morphology of the bacterial cell could be affected. The effect was suggested to be due to electrostatic interaction with the pos-itively charged modified fibres. The promising results offer the possibilities of a new generation of antibacterial surfaces based on a renewable resource. / Antibakteriella kontaktaktiva ytor som har ett antibakteriellt ämne permanent fäst på ytan är ett miljövänligt och säkrare alternativ till traditionell biocidanvändning. Inget utsläpp av giftiga ämnen sker från ytorna och detta tillsammans med den anti-bakteriella mekanismen minskar risken för att bakterierna utvecklar resistens. Till-verkningsprocessen i sig har dock hittills varit allt annat än miljövänlig, då den ke-miska modifieringen kräver organiska lösningsmedel och har reaktioner som kräver speciella villkor, t ex höga temperaturer. En alternativ ytmodifiering är att använda sig av fysikalisk adsorption av polyelektrolyter i multiskikt, eftersom detta kan göras i vat-tenlösningar och i rumstemperatur. Det här arbetet är det första som beskriver kon-takt-aktiva multilager på förnyelsebara svedbaserade cellulosafiber. Som ett första steg gjordes en adsorptionsstudie på modellytor för att optimera ad-sorptionen av katjonisk polyvinylamin (PVAm) och anjonisk polyakrylsyra (PAA). Med ökande antal lager ökade totala mängden adsorberad polymer samtidigt som multilagerna förblev platta och täta. Den högsta adsorptionen skedde vid en hög salt-halt som minimerade den elektrostatiska repulsionen mellan polymerkedjorna. Modellytor användes även för att studera hur de antibakteriella egenskaperna påver-kades av polymermodifiering och av antal lager. På dessa ytor uppmättes en låg bakte-riostatisk effekt med upp till 40 % inhibering av bakterietillväxten för tre lager av PVAm./PAA När däremot samma multilager fanns på cellulosafiber ökade in-hiberingen till uppemot 99.9 %. Hydrofobmodifiering av PVAm påverkade inte det antibakteriella resultatet när de var i multilager, trots bevisad ökad verkan i lösning. Genom att via oxidering öka fiberladdningen kunde mängden adsorberad polymer yt-terligare öka och resulterade i en förbättrad antibakteriell verkan som höll i sig i flera veckor. Elektronmikroskopi av bakterier på fiber visade en ökad interaktion med hög-laddade ytor och att bakteriernas cellmorfologi kan påverkas av ytorna.Den observerade antibakteriella effekten föreslås vara en följd av elektrostatisk inter-aktion mellan de negativt laddade bakterierna och positivt laddade modifierade fibrena. Resultaten är lovande och banar väg för nya kontakt-aktiva antibakteriella material. / Biointeractive fibres with antibacterial properties

No description available.

A dissertation submitted In fulfilment of the degree Doctor of Philosophy (Chemistry) In the Faculty of Science School of Chemistry University of the Witwatersrand. Johannesburg 2015. / According to the World Health Organization (WHO), cancer is a leading cause of death worldwide and has accounted for 7.6 million deaths (13% of all deaths) in 2008. The number of effective drugs available has been reduced by chemo resistant malignant tumors. Similarly, bacterial infections are one of the world’s most pressing public health problem. The major challenge in anti-bacterial treatment is due to the development of bacteria strains that are resistant to antibiotics. Each year more than 11 million people die from major infections such as MDR tuberculosis. In 2013, 9 million people fell ill with TB and 1.5 million died from the disease (WHO). Therefore there is a need for novel therapeutic alternatives such as the discovery of new anti-cancer and anti-bacterial agents. Benzofurans have attracted much attention due to their broad spectrum of pharmacological activities such as anti-cancer and anti-bacterial activities and one classical example is usnic acid. Most of the published synthesis of the benzofuran moiety involved the formation of annellated furan ring by intramolecular cyclisation of benzene, and these procedures involved a multi-step, rigorous reaction conditions and expensive catalyst. This research investigated the novel synthesis of benzofurans through the application of biocatalysis, where the reactions involved the use of the oxidative enzyme laccase to generate carbon-carbon bonds, carbon-oxygen and carbonnitrogen bonds between aromatic compounds. The substrates used were o-diols from catechols 1, p-quinone 2 from naphthoquinones and naphthohydroquinone 3, which, when activated by the enzyme action, could be reacted with 1,3-diketones 4, 5 or coumarins 6 (Figure 1). The aim of synthesising different classes of compounds was to vary the functional groups and to increase the number of rings, so as to possibly increase the biological activities.

Thesis (MSc (Chemistry and Biochemistry))--University of Limpopo, 2009. / Rhus leptodictya is a member of the Anacardiaceae (mango family) and is used for treating bacteria related disease by indigenous cultures in South Africa. Domestic animals feed on the tree during times of drought and this apparently does not cause as much tainting of milk, as when stock feed on the related Rhus lancea. Beer is brewed from the fruits of R. leptodictya and various parts are used in traditional medicine. The Manyika people use powdered roots of R. leptodictya for acute pain in the chest and abdominal areas. The Xhosa people use roots for gall sickness in cattle. A lotion of branches and smoke from burning is used for eye complaints by Swati people. The main aim of the study was to evaluate the antibacterial activity of extracts of the leaves and twigs of R. leptodictya in order to confirm the traditional use and then to isolate and characterize antibacterial compounds. To determine the best extractants for the extraction of antibacterial compounds from the dried leaves and twigs of R. leptodictya, the efficacy of several extractants was determined. Seven different solvents of varying polarity hexane (Hex), chloroform (Chl), dichloromethane (DCM), ethyl acetate (Eth), acetone (Act), methanol (Met) and water (Wat) were used in serial extraction to extract compounds from the leaves and twigs. The mass extracted from 4g by different solvents ranged from 43-965 mg of dry weight. The plant extracts with the highest yield was the DCM extract followed by the methanol and acetone extracts. Thin layer chromatography (TLC) was used to analyze the chemical composition of the extracts using three eluent solvent systems of varying polarities i.e. CEF, BEA and EMW and sprayed with vanillin-sulphuric acid. The chemical composition of the different extracts was vii similar with the exception of methanol and water extracts, which had only one or two visible compounds after treating with vanillin spray reagent. Chromatograms developed in three different solvent systems (CEF, BEA and EMW) were sprayed with 2, 2-diphenylpicrylhydrazyl (DPPH) to evaluate antioxidant activity. There were few antioxidant compounds present. To evaluate the number of antibacterial compounds present in the fractions, bioautography was used against four most important nosocomial microorganisms. S. aureus, E. faecalis, P. aeruginosa and E. coli. Nearly all the crude serial extraction fractions contained compounds that inhibited the growth of S. aureus. The acetone fraction had the most lines of inhibition (6) followed by ethyl acetate (5). For quantitative evaluation of antibacterial activity, minimum inhibitory concentration (MIC) values were determined using a serial microplate dilution method. The MIC values for all the fractions against all the bacterial pathogens varied from 0.04-0.63 mg/ml. The acetone extract was the most active against four bacteria with the average MIC value of 0.36 mg/ml. Leaves and twigs were extracted in bulk with acetone and solvent-solvent extraction was employed which yielded seven fractions. Bioassay guided fractionation against S. aureus was used to isolate antibacterial compounds. The largest number of antibacterial compounds occurred in the carbon tetrachloride fraction. This fraction was subjected to silica gel column chromatography eluting with eluents of increasing polarity. Two pure compounds were isolated. These compounds were identified using NMR spectroscopy and mass spectroscopy, as 2, 3 dihydro-amentoflavone and lutein. The compounds had good activity against different bacteria with MIC values ranging from 20 to 60 μg/ml. Isolated compounds were investigated for cytotoxicity against Vero cells with an LC50 of 9.4 μg/ml for lutein and 9.8 μg/ml for 2.3- viii dihydro amentoflavone which indicated toxicity. The much higher toxicity against mammalian cells than again bacterial cells indicate that these compounds do not have a good therapeutic potential but support the external use for the treatment of wounds. This is the first report of these compounds from Rhus leptodictya. The results provide scientific support for the use of R. leptodictya in treating bacterial infection in humans and animals.

In a first step, the surfaces of polyethylene films have been modified by grafting urethane monoacrylate monomer under UV irradiation in ambient air. For native films, this grafting was successfully realized but the grafted surface was heterogeneous. To overcome this drawback and obtain a smooth and homogeneous coating, a wet oxidation method using sodium hypochlorite through two different processes was developed. The oxidation mechanism of the PE films has been established. As a consequence of the oxidation, the wettability of the grafted films was strongly increased as measured by sessile drop technique and Wilhelmy plate method. The hydrophilicity is due to carbonyl and carboxylic groups created on the treated surface. Grafting of several formulations containing different amounts of monomer, carrier and photosensitizer was successfully evidenced by analyzing the residues obtained from PE extraction in hot toluene. Indeed, FTIR, XPS, DSC and elementary analysis showed that the polyacrylate was effectively grafted on PE pre-oxidized films. Moreover, the obtained grafted surfaces corresponding to important oxidation time were homogeneous as shown by SEM and AFM. In a second step, acrylate grafting was used to induce specific properties onto the surface. This study was focused on antibacterial effect. The process starts by a dissolution of poly(4-vinylbenzyl chloride) (PVBC) in the urethane monoacrylate monomer followed by photopolymerisation of the latter. Anchoring of different PVBC based formulations was confirmed by FTIR analysis, performed onto obtained residues after extraction in hot toluene and dichloromethane. In a last step, the grafted coatings were quaternized by using triethylamine in N, N-dimethyl formamide by a nucleophilic displacement reaction. Antibacterial effect of the quaternized samples was measured by Kirby Bauer method.

In a first step, the surfaces of polyethylene films have been modified by grafting urethane monoacrylate monomer under UV irradiation in ambient air. For native films, this grafting was successfully realized but the grafted surface was heterogeneous. To overcome this drawback and obtain a smooth and homogeneous coating, a wet oxidation method using sodium hypochlorite through two different processes was developed. The oxidation mechanism of the PE films has been established. As a consequence of the oxidation, the wettability of the grafted films was strongly increased as measured by sessile drop technique and Wilhelmy plate method. The hydrophilicity is due to carbonyl and carboxylic groups created on the treated surface. Grafting of several formulations containing different amounts of monomer, carrier and photosensitizer was successfully evidenced by analyzing the residues obtained from PE extraction in hot toluene. Indeed, FTIR, XPS, DSC and elementary analysis showed that the polyacrylate was effectively grafted on PE pre-oxidized films. Moreover, the obtained grafted surfaces corresponding to important oxidation time were homogeneous as shown by SEM and AFM. In a second step, acrylate grafting was used to induce specific properties onto the surface. This study was focused on antibacterial effect. The process starts by a dissolution of poly(4-vinylbenzyl chloride) (PVBC) in the urethane monoacrylate monomer followed by photopolymerisation of the latter. Anchoring of different PVBC based formulations was confirmed by FTIR analysis, performed onto obtained residues after extraction in hot toluene and dichloromethane. In a last step, the grafted coatings were quaternized by using triethylamine in N, N-dimethyl formamide by a nucleophilic displacement reaction. Antibacterial effect of the quaternized samples was measured by Kirby Bauer method.

Extracts of 16 South African Salvia species commonly used in traditional medicine to treat various microbial infections were investigated for in vitro antibacterial and antimycobacterial activities using the micro-dilution and respiratory BACTEC method, respectively. The microorganisms tested include two Gram-positive (Staphylococcus aureus and Bacillus cereus); two Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacterial strains and the common pathogen responsible for tuberculosis, Mycobacterium tuberculosis. Extracts of the majority of species exhibited moderate to good antibacterial activity with minimum inhibitory concentration (MIC) values ranging from 0.03 to 8.00 mg/ml. Promising activity was observed against M. tuberculosis (MIC≤0.50 mg/ml) with S. radula, S. verbenaca and S. dolomitica displaying the most favourable activity (MIC: 0.10 mg/ml). The antibacterial bioassay-guided fractionation of S. chamelaeagnea resulted in the isolation of four compounds: carnosol, 7-O-methylepirosmanol, oleanolic acid and its isomer ursolic acid as the active principles against S. aureus. The in vitro antibacterial and antimycobacterial activities may support the use of Salvia species in traditional medicine to treat microbial infections.