John R. Bartlett

Antioxidant and anti-inflammatory activities of selected medicinal plants containing phenolic and flavonoid compounds

The antioxidant, anti-inflammatory, and cytotoxic activities of water and ethanol extracts of 14 Chinese medicinal plants were investigated and also their total phenolics and flavonoid contents measured. The antioxidant activity was evaluated in a biological assay using Saccharomyces cerevisiae , whereas the radical scavenging activity was measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Total phenolics and flavonoid contents were estimated by Folin-Ciocalteu and aluminum chloride methods, respectively. The anti-inflammatory activities of the plant extracts were determined by measuring the inhibition of production of nitric oxide (NO) and TNF-α in LPS and IFN-γ activated RAW 264.7 macrophages. Their cytotoxic activities against macrophages were determined by Alamar Blue assay. Four plants, namely, Scutellaria baicalensis , Taxillus chinensis , Rheum officinale , and Sophora japonica , showed significant antioxidant activity in both yeast model and also free radical scavenging methods. The ethanol extract of S. japonica showed highest levels of phenolics and flavonoids (91.33 GAE mg/g and 151.86 QE mg/g, respectively). A positive linear correlation between antioxidant activity and the total phenolics and flavonoid contents indicates that these compounds are likely to be the main antioxidants contributing to the observed activities. Five plant extracts (S. baicalensis, T. chinensis, S. japonica, Mahonia fortunei , and Sophora flavescens ) exhibited significant anti-inflammatory activity by in vitro inhibition of the production of NO and TNF-α with low IC(50) values. These findings suggest that some of the medicinal herbs studied in this paper are good sources of antioxidants.

Antioxidant and anti-inflammatory activities of selected Chinese medicinal plants and their relation with antioxidant content

BackgroundThe main aim of this study is to evaluate the antioxidant and anti-inflammatory properties of forty four traditional Chinese medicinal herbal extracts and to examine these activities in relation to their antioxidant content.MethodsThe antioxidant activities were investigated using DPPH radical scavenging method and yeast model. The anti-inflammatory properties of the herbal extracts were evaluated by measuring their ability to inhibit the production of nitric oxide and TNF-α in RAW 264.7 macrophages activated by LPS and IFN- γ, respectively. The cytotoxic effects of the herbal extracts were determined by Alomar Blue assay by measuring cell viability. In order to understand the variation of antioxidant activities of herbal extracts with their antioxidant contents, the total phenolics, total flavonoids and trace metal (Mg, Mn, Cu, Zn, Se and Mo) quantities were estimated and a correlation analysis was carried out.ResultsResults of this study show that significant levels of phenolics, flavonoids and trace metal contents were found in Ligustrum lucidum, Paeonia suffuticosa, Salvia miltiorrhiza, Sanguisorba officinalis, Spatholobus suberectus, Tussilago farfara and Uncaria rhyncophylla, which correlated well with their antioxidant and anti-inflammatory activities. Some of the plants displayed high antioxidant and anti-inflammatory activities but contained low levels of phenolics and flavonoids. Interestingly, these plants contained significant levels of trace metals (such as Zn, Mg and Se) which are likely to be responsible for their activities.ConclusionsThe results indicate that the phenolics, flavonoids and trace metals play an important role in the antioxidant activities of medicinal plants. Many of the plants studied here have been identified as potential sources of new antioxidant compounds.

Fourier transform Raman spectroscopy of kandite clays

The Raman spectra of the kandite clay minerals, kaolinite, halloysite, dickite and nacrite, have been measured in the 180–3000 cm−1 region using Fourier transform near-IR Raman spectroscopy. These clays have a very small Raman cross-section and long data collection times were often required to obtain good spectra. Each clay has its own unique characteristic Raman spectrum which enables each kandite to be identified easily. In contrast, it is quite difficult to distinguish kandite clays by IR spectroscopy. Nacrite and dickite have relatively intense Raman peaks in the 1000–1100 cm−1 region, whereas kaolinite is characterized by an intense peak at 685 cm−1 and halloysite at 470 cm−1.

Atomic layer deposition of TiO2 and Al2O3 thin films and nanolaminates

We have been developing our capability with atomic layer deposition (ALD), to understand the influence of deposition parameters on the nature of TiO2 and Al2O3 films (high and low refractive index respectively), and multilayer stacks thereof (nanolaminates). These stacks have potential applications as anti-reflection coatings and optical filters. This paper will explore the evolution of structure in our films as a function of deposition parameters including temperature and substrate surface chemistry. A broad range of techniques have been applied to the study of these films, including cross-sectional transmission electron microscopy, spectroscopic ellipsometry and secondary-ion mass spectrometry. These have enabled a wealth of microstructural and compositional information on the films to be acquired, such as accurate film thickness, composition, crystallization sequence and orientation with respect to the substrate. The ALD method is shown to produce single-layer films and multilayer stacks with exceptional uniformity and flatness, and in the case of stacks, chemically abrupt interfaces. We are currently extending this technology to the coating of polymeric substrates.

Eu3+-Based Bridged Silsesquioxanes for Transparent Luminescent Solar Concentrators

The sol-gel preparation of a bridged silsesquioxane containing europium(III) salts and 2-thenoyltrifluoroacetone has been achieved from a new ethane tetracarboxamide-based organosilane. Free-standing films with thicknesses up to 440 μm and maximum absolute quantum yield (q) of 0.34 ± 0.03 (excitation at 320 nm) were prepared by the drop cast method, while thin films (∼200-400 nm) spin-coated on glass substrates led to highly luminescent coatings with q = 0.60 ± 0.02 (excitation at 345 nm). The thin films were tested as planar luminescent solar concentrators and the optimized device displays an optical conversion efficiency of 12.3% in the absorbing spectral region of the active layer (300-380 nm).

Anti-fungal and anti-bacterial activities of ethanol extracts of selected traditional Chinese medicinal herbs.

OBJECTIVE To evaluate in vitro antimicrobial activities of selected 58 ethno-medicinal plant extracts with a view to assess their therapeutic potential. METHODS A total of 58 traditional Chinese medicinal plants were carefully selected based on the literature review and their traditional use. The antimicrobial activities of ethanol extracts of these medicinal plants were tested against fungi (Aspergillus fumigatus), yeast (Candida albicans), gram-negative (Acinetobacter baumannii and Pseudomonas aeruginosa) and gram-positive bacteria (Staphylococcus aureus). The activities were tested at three different concentrations of 1.00, 0.10 and 0.01 mg/mL. The data was analysed using Gene data Screener program. RESULTS The measured antimicrobial activities indicated that out of the 58 plant extracts, 15 extracts showed anti-fungal activity and 23 extracts exhibited anti-bacterial activity. Eight plant extracts have exhibited both anti-bacterial and anti-fungal activities. For instance, Eucommia ulmoides, Polygonum cuspidatum, Poria cocos and Uncaria rhyncophylla showed activity against both bacterial and fungal strains, indicating their broad spectrum of activity. CONCLUSIONS The results revealed that the ethanol extracts of 30 plants out of the selected 58 possess significant antimicrobial activities. It is interesting to note that the findings from the current study are consistent with the traditional use. A clear correlation has also been found between the antimicrobial activity and the flavonoid content of the plant extracts which is in agreement with the literature. Hence, the results presented here can be used to guide the selection of potential plant species for the isolation and structure elucidation of novel antimicrobial compounds in order to establish the structure-activity relationship. This in turn is expected to lead the way to the discovery of novel antimicrobial agents for therapeutic use.

Production of Titanate Microspheres by Sol-Gel and Spray-Drying

Porous titanate precursor microspheres (20–60 μm in diameter), with a high sorption capacity for radioactive wastes from nuclear reprocessing plants, have been produced on a 50 kg scale by spray-drying precursor sols. Well-dispersed, stable sols were produced by hydrolyzing acetic acid modified tetraisopropyltitanate and peptizing the titania hydrolysate with acidic zirconia sol. The resulting TiO2 /ZrO2 sols were routinely concentrated to 900 g dm−3 (oxide basis) and exhibited excellent stability. These sols were subsequently mixed with dispersible alumina powder and partially aggregated by adding calcium and barium nitrate salts. The resulting sols were spray-dried to produce microspheres with controlled porosity and morphology. The properties of the spray-dried powder were very dependent upon the chemical properties of the precursor sol. In particular, hollow spheres were produced from well-dispersed sols, whereas solid spheres could be produced from partially-aggregated sols.

Formation of TiO2 Sols, Gels and Nanopowders from Hydrolysis of Ti(OiPr)4 in AOT Reverse Micelles

Titania sols, gels and nanopowders have been produced by the controlled hydrolysis of tetraisopropyltitanate (TPT) in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles. Particle formation and aggregation have been investigated by photon correlation spectroscopy, the crystal phases by FT-Raman spectroscopy, and the crystallite dimensions of the precipitates by transmission electron microscopy. Nanoparticles could be produced at relatively high Ti(IV) concentrations (up to 0.05 mol dm−3). These nanoparticles aggregated into sols, with colloid sizes of 20–300 nm, eventually forming gelatinous precipitates. The kinetics of particle formation and aggregation were controlled by varying the primary process parameters [TPT], [H2O]/[AOT] (w0), and [H2O]/[Ti(IV)] (R), yielding a range of products including stable, transparent sols, precipitates and monolithic gels. The aggregation kinetics and physical properties of the sols depended strongly on w0. Different titania phases were produced, depending on w0; w0 ≤ 6 yielded amorphous particles, while w0 ≥ 10 produced anatase. The dimensions of the crystallites were comparable to those of the parent reverse micelles. A model was developed to interpret the effect of the primary process parameters on colloidal stability: (1) nucleation to form primary crystallites occurs by rapid hydrolysis and condensation reactions within the reverse micelle and (2) subsequent colloidal growth by aggregation occurs by reverse micellar exchange, where the rate of growth is governed by electrostatic and steric stability factors which increase as [AOT]/[TPT] (S) and residual [H2O]/[AOT] (wr) increase.

The Effect of Precursor Chemistry on the Crystallisation and Densification of Sol-Gel Derived Mullite Gels and Powders

Stoichiometric and silica-rich mullite gels and powders were prepared using four different sol-gel methods. Thermal analysis, X-ray powder diffraction and dilatometry techniques were used to investigate the thermal decomposition, crystallisation and sintering of these mullite precursor gels. The method of preparation, by controlled hydrolysis of various mixtures of tetraethylorthosilicate, aluminium sec-butoxide and aluminium nitrate, affected the texture of the gels, producing single-phase or diphasic samples.The crystallisation sequence of the gels depended on the composition and method of preparation. Single phase mullite crystallised from homogeneous gels at 980°C, while diphasic gels initially formed of a mixture of γ-Al2O3 spinel and mullite, or simple γ-Al2O3 spinel, which subsequently transformed to mullite at 1260°C.Dilatometry and density measurement were used to investigate the sintering of compacts formed by pressing powders prepared from gels precalcined at 500°C. Varying the heating rates from 2 to 10°C min-1 had little effect on the densification to 1500°C. However, the densification rate was sensitive to the degree of crystallinity and the amount and type of phases present at the sintering temperature. The presence of γ-Al2O3 spinel in the structure initially promoted densification, but the sintering rate was reduced considerably after mullite crystallised. Diphasic materials, especially those with an excess amount of silica in the original gel, sintered to higher densities due to the presence of excess silica promoting densification by viscous phase sintering.

Luminescent coatings from bipyridine-based bridged silsesquioxanes containing Eu3+ and Tb3+ salts

The sol–gel fabrication of bridged silsesquioxane thin films containing trivalent lanthanide ions (Ln3+) has been achieved from a 4,4′-diureido-2,2′-bipyridine bridged organosilane (P4) in the presence of Eu3+ or Tb3+ salts. Crack- and defect-free thin films (∼50 nm) of optical quality were successfully deposited on glass substrates by spin-coating after optimizing the spinning rate and solvent system. Ellipsometry investigations revealed a significant decrease in the refractive index of the films with ageing of the corresponding precursor sols. In contrast, the photoluminescence properties of the films are independent of precursor ageing time, although significant differences are observed with respect to the corresponding bulk materials. Compared to the bulk materials, the films exhibit a significant blue-shift of the excitation spectra and an increase of the excited state lifetime. The optical conversion efficiencies (ηopt) of the F4-Eu and F4-Tb-based collectors were also determined and potential applications of the coatings in such areas as luminescent solar concentrators are discussed.