Preparation, spectroscopic and acidity properties of two hydrazones: an organic lab experiment

An undergraduate organic lab experiment is described based on the preparation of two readily accessible hydrazones. The UV-visible spectra of these N-H acids and of their conjugate bases are employed to illustrate the importance of through-conjugation in determining their acid strength and their internal charge-transfer-band transitions.

Preparation of Polysulfone Membranes

As it is known, a huge part of all commercially available membranes are prepared by immersion precipitation. This way is the primary way to get flat membranes. The advantages of immersion precipitation are: wide field of the polymers, which can be used (polymer must be soluble in a solvent or a solvent mixture) and ease of performing. The literature part of this work deals with phase inversion membrane preparation methods and casting parameters affecting membrane performance. Also some membrane types and materials are discussed. In the experimental part of this work 73 membrane samples were made with different casting parameters (polymer concentration in the casting solution and precipitation time) and tested for the retention and permeability. The results of these experiments are collected and combined into the figures and tables which are presented in this thesis. This work showed and confirmed connection between membrane performance and casting parameters (concentration of polymer in the casting solution and precipitation time).

Chemical constituents from Tabernaemontana catharinensis root bark: a brief NMR review of indole alkaloids and in vitro cytotoxicity

This work describes the isolation and structural determination of pharmacological compounds present in the bark of roots of Tabernaemontana catharinensis (Apocynaceae). Among the 27 substances detected 12 were identified as terpenoid-indole alkaloids, 2 steroids and 13 pentacyclic triterpenes. Structures were outlined based on HMQC, COSY, DEPT, 13C, and ¹H NMR data and MS. Spectral data of indole alkaloids were reviewed. An in vitro screening of the extracts and isolated compounds was carried out. Compounds ibogamine (5), 3-oxo-coronaridine (9) and 12-methoxy-4-methylvoachalotine (MMV) demonstrated effective cytotoxicity towards SKBR-3 breast adenocarcinoma and C-8161 human melanoma tumor cell lines.

Decrease in the diversity of pyrrolizidine alkaloids of Senecio pterophorus after invasion

Pyrrolizidine alkaloids (PAs) are N-based plant secondary metabolites that function as chemical defenses against vertebrate and invertebrate herbivores. PAs can be highly variable at intraspecific level, both in their absolute and relative concentrations. Changes in the chemical composition of exotic plants when they invade a new environment have been poorly explored. Here we studied the biogeographical variation on PAs in Senecio pterophorus (Asteraceae) in the native region in Eastern South Africa, an expanded region in Western South Africa, and two introduced regions in Australia and Europe. PAs in S. pterophorus were represented by the highly toxic 1,2-unsaturated PAs and the less toxic 1,2-saturated PAs. Our results show a change in the plant chemical composition after invasion. Total PAs concentrations were highest in Australia compared to any other region. Plants from Europe contained the highest relative concentrations of 1,2-saturated PAs. The positive correlation between the chemical and the genetic distances estimated between populations suggests that the chemical profiles in the non-native regions were related to the plant dispersal routes. The decrease in the chemical diversity and the change in the absolute PAs concentrations in S. pterophorus after invasion may have consequences in the interactions between plants and herbivores in the novel habitats.

Vanadium-modified molecular sieves: preparation, characterization and catalysis

Vanadium-containing molecular sieves are redox catalysts and are good candidates as substitutes for oxide-supported V2O5 in a number of reactions. These materials have the advantage of presenting better dispersion of vanadium species, as well as shape-selective properties and controllable acidities. They may be prepared by one-pot synthesis or by post-synthesis methods and a number of techniques such as diffuse reflectance UV-visible spectroscopy, 51V nuclear magnetic resonance and electron paramagnetic resonance, to name but a few, have been used to characterize these materials. In this review, methods of preparation of vanadium-modified molecular sieves, their characterization and applications in catalysis are discussed.

Preparation and characterization oF Ru-Sn/Al2O3 catalysts for the hydrogenation of fatty acid methyl esters

Ru-Sn/Al2O3 catalysts with different Sn loadings were prepared by the coimpregnation method. Several characterization techniques such as TPR, pyridine TPD and catalytic tests for dehydrogenation and hydrogenolysis were used to evaluate and compare such catalysts. TPR results indicate that Sn is deposited both onto the support and as species strongly interacting with Ru. Such non selective deposition modifies the acid and metallic functions of the catalysts. Both total acidity and acid strength distribution are affected: total acidity decreases and new sites of lower acid strength are created. Both dehydrogenating and hydrogenolytic activities are strongly diminished by the addition of Sn. Results of catalytic tests for methyl oleate hydrogenation indicate that methyl stearate is the main product, with only minute amounts of oleyl alcohol produced, and that the addition of Sn diminishes the hydrogenation activity.

Aporphine alkaloids from Ocotea macrophylla (Lauraceae)

Four aporphine alkaloids from the wood of Ocotea macrophylla (Lauraceae) were isolated and characterized as (S)-3-methoxy-nordomesticine (1), (S)-N-ethoxycarbonyl-3-methoxy-nordomesticine (2), (S)-N-formyl-3-methoxy-nordomesticine (3) and (S)-N-methoxycarbonyl-3-methoxy-nordomesticine (4); alkaloids 2-4 are being report for the first time. The structure the isolated compounds were determined based on their spectral data and by comparison of their spectral data with values described in literature. The alkaloid fraction and compound 1 showed antifungal activity against Fusarium oxysporum f. sp. lycopersici and also compound 1 showed antimicrobial activity towards Staphylococcus aureus, Enterococcus faecalis as well.

Preparation of PVP hydrogel nanoparticles using lecithin vesicles

Hydrogels micro, sub-micro and nanoparticles are of great interest for drug encapsulation and delivery or as embolotherapic agents. In this work it is described the preparation of nano and sub-microparticles of pre-formed, high molecular weight and monomer free poly(N-vinyl-2-pyrrolidone) encapsulated inside the core of lecithin vesicles. The hydrogel particles are formed with a very narrow diameter distribution, of about 800 nm, and a moderate swelling ratio, of approximately 10.

Bromopyrrole alkaloids from the caribbean sponge Agelas cerebrum

Bioguided fractionation of Agelas cerebrum crude extract resulted in isolation of four bromopyrrole and four bromopyrrole aminoimidazole alkaloids, identified as 5-bromopyrrole-2-carboxylic acid (1), 4-bromopyrrole-2-carboxylic acid (2), 3,4-bromopyrrole-2-carboxylic acid (3), 4,5-bromopyrrole-2-carboxylic acid (4), oroidin (5), bromoageliferin (6), dibromoageliferin (7) and dibromosceptrin (8) on the basis of spectroscopic data analyses (UV, IR, HRMS, 1D and 2D NMR) and comparison with literature data. This is the first report of compounds 2 and 3 in a marine sponge belonging to the Agelas genus and the first evidence of the presence of 1 from a natural source.

Anxiolytic-like effects of erythrinian alkaloids from erythrina suberosa

Two alkaloids, erysodine (1) and erysothrine (2) were isolated from the flowers of a Pakistani medicinal plant, Erythrina suberosa. These compounds were investigated for anxiolytic properties, and the results showed significant effect, in an acute oral treatment with 1-2, which were suspended in saline (NaCl 0.9%) plus DMSO 1%, and evaluated in 122 Swiss male mice exposed to two tests of anxiety - the elevated plus-maze (EPM) and the light/dark transition model (LDTM).

Quinoline alkaloids and friedelane-type triterpenes isolated from leaves and wood of Esenbeckia alata kunt (Rutaceae)

This work describes the phytochemical exploration of the ethanol extract from leaves and wood of Esenbeckia alata, leading to the isolation and identification of quinoline alkaloids 4-methoxy-3-(3'-methyl-but-2'-enyl)-N-methyl-quinolin-2(1 H)-one, N-methylflindersine, dictamine, kokusaginine, Γ-fagarine, flindersiamine, as well as the fridelane-type triterpenes, frideline, fridelanol and its acetate derivative. Identification of these compounds was based on full analyses of spectroscopic data (¹H, 13C, 1D, 2D, IR, MS) and comparison with data reported in literature. Compound 4-methoxy-3-(3'-methyl-but-2'-enyl)-N-methyl-quinolin-2(1 H)-one is reported for the first time for the genus Esenbeckia.

Pyrrolizidine alkaloids of senecio sp from Peru

Six pyrrolizidine alkaloids (PAs) (two saturated macrocyclic, three unsaturated macrocyclic and one unsaturated seco-macrocyclic) were isolated from native Peruvian Senecio species. The structures of these alkaloids were established by a complete NMR spectroscopic analysis, chemical transformations and comparison of their NMR data with those published for similar alkaloids. Three PAs were then tested for antifungal activity against Fusarium moniliforme, F. (Sheldon), F. oxysporum fs. lycopersici (Scheldt) and F. solani (Mart), no significant activity being observed.

Preparation of glasses and glass ceramics of heavy metal oxides containing silver: optical, structural and electrochemical properties

Silver containing heavy metal oxide glasses and glass ceramics of the system WO3-SbPO4-PbO-AgCl with different AgCl contents have been prepared and their thermal, structural and optical properties characterized. Glass ceramics containing metallic silver nanoparticles have been prepared by annealing glass samples at temperatures above the glass transition and analyzed by transmission electron microscopy and energy dispersive X-ray microanalysis. The presence of the metallic clusters has been also confirmed by the observation of a surface plasmon resonance band in the visible range. Cyclic voltammetric measurements indicated the presence of metallic silver into the glasses, even before to perform the thermal treatment.

Preparation of association compound between rhodium(II) citrate and β-cyclodextrin

Inclusion compound of rhodium(II) citrate with β-cyclodextrin in a 1:1 molar ratio was prepared using freeze-drying method. X-ray diffactometry, thermal analysis (TG/DTG/DSC), infrared and ¹H-NMR with ¹H spin lattice relaxation (¹H T1) measurements and 13C techniques were used to characterize the system prepared. The results indicated the formation of inclusion or association compounds between rhodium(II) citrate and β-cyclodextrin.

Sonication-assisted preparation of CaO nanoparticles for antibacterial agents

The effect of calcination conditions on the size and killing activity of CaO nanoparticles towards L. plantarum was studied in this paper. The results showed that CaO nanoparticles with a diameter of 20 nm could be obtained under the investigated conditions. The lethal effect of CaO nanoparticles after incubation of 6 or 24 h increased with increasing calcination time. Using CaO-SA, CaO-SB, and CaO-SC after a 24-h exposure, 2.25, 3.37, and 5.97 log L. plantarum were killed, respectively, at a concentration of 100 ppm. The current results show that the use of CaO nanoparticles as antibacterial agents has significant potential in food-relevant industries.