Novel microbial transformation of resibufogenin by Absidia coerules

Resibufogenin is one of the major active components of the Chinese medicine ChanSu. In this paper, microbial transformation of resibufogenin by Absidia coerules AS 3.3382 was investigated and five metabolites were isolated and identified as 5beta-hydroxy-resibufogenin (2), 3-epi-resibufogenin (3), 3alpha-hydroxy-15-oxo-14alphaH-bufa-20, 22-dienolide (4), 3alpha,14alpha,15beta-trihydroxy-bufa-20, 22-dienolide (5) and 3-epi-15beta-hydroxy-bufalin (6). Among them, 4-6 are novel compounds, and compound 3 is a major transformed product. The cytotoxicities of the compounds against Bel-7402 and Hela cells were investigated, and our result suggested that 14,15-OH configuration was directly related to the cytotoxicities of bufadienolides.     

Structural properties of hydroxyapatite obtained by mechanosynthesis

In this paper mechanical alloying has been used successfully to produce nanocrystalline powders of hydroxyapatite (HA) using five different experimental procedures in a pure dry process. The milled HA were studied by X-ray powder diffraction, infrared and Raman scattering spectroscopy. For four different procedures, HA was obtained after a couple of hours of milling (in average 60 hours of milling, depending in the reaction procedure). This milling process, used to produce HA, presents the advantage that melting is not necessary and the powder obtained is nanocrystalline with crystallite size in the range of 22 nm to 39 nm.     

Four novel metabolites from microbial transformation of curcumol by Cunninghamella blakesleana

Further study on the microbial transformation of curcumol (1) by Cunninghamella blakesleana (AS3.970) led to the isolation of four novel metabolites. Their structures were elucidated as 3beta-hydroxy curcumol (2), 12-hydroxy curcumol (3), 1alpha-hydroxy-10beta,14-epoxy curcumol (4) and (2S,4S,5S,7S)-10-hydroxymethyl-7-isopropyl-2-methoxy-4-methyl-1-oxaspiro[4,6]undec-10-en-8-one (5) on the basis of spectral methods. All of them were characterized as new compounds.     

Two new triterpenoid saponins obtained by microbial hydrolysis with Alternaria alternata AS 3.6872

Compound 1, a triterpenoid saponin from Ardisia gigantifolia Stapf showing potential anti-tumour activity, was hydrolysed into two deglycosyl derivatives (2 and 3) by Alternaria alternata AS 3.6872. Both these derivatives are new compounds. Their structures were elucidated on the basis of 1D, 2D NMR, HR-ESI-MS and optical rotation spectral data. Compounds 1–3 were evaluated for their cytotoxicity against human hepatocellular carcinoma and normal liver cells by Cell Counting Kit 8 colorimetric assay.     

Photoelectrochemical properties of TiO2 films obtained by electrical explosion

The electrical explosion of wires was used to prepare titanium dioxide nanopowders alloyed with silver nanoparticles. The photoelectrochemical properties and electronic structure of these materials were studied. The quantum yield for the photoelectrochemical current η and the flat band potential E _fb for TiO₂/Ag films were found to be proportional to the content of the Ag⁰ phase on the electrode surface.     

Comparative properties of Amazonian oils obtained by different extraction methods

Pequi (Caryocar brasiliense Camb.), baba?u (Orbignya phalerata Mart.), buriti (Mauritia flexuosa), and passion fruit (Passiflora edulis) oils were studied to determine their antibacterial, antioxidant and cytotoxic activities, as well as their total phenol and carotenoid contents. The fatty acid contents were determined by GC-MS. The three types of passion fruit oils studied were refined, cold pressed or extracted from seeds in a Soxhlet apparatus. The oils thus obtained showed differences in antioxidant activity and carotenoid content, but were similar in regard to total phenols. Buriti and pequi had the highest carotenoid contents, while refined and cold pressed passion fruit oil displayed the highest antioxidant activity. Pequi oil was the only oil to display antibacterial and cytotoxic activity.     

Structural determination of three new germacrane-type sesquiterpene alcohols from curdione by microbial transformation

Five germacrane-type sesquiterpene alcohols obtained from curdione (1) by microbial biotransformation were isolated. Their structures were characterized as (2R)-2beta-hydroxycurdione (2), 1alpha, 10beta-epoxy-11-hydroxycurdione (3), (2S)-2alpha, 11-dihydroxycurdione (4), 11,15-dihydroxycurdione (5) and (3R)-3alpha-hydroxycurdione (6) based on the extensive NMR studies. Among them, 4, 5 and 6 are new compounds.     

Synthesis and properties of UV-curable polysiloxane methacrylate obtained by one-step method

In this study, a UV-curable polysiloxane methacrylate (PSMA) was synthesized by a one-step method. The reaction was catalyzed by chloroplatinic acid between polymethylhydrosiloxane (PMHS) and hydroxyethyl methacrylate (HEMA), as proved by FTIR and ¹H-NMR. The preliminary results indicate that the obtained UV-cured PSMA film has very good thermal stability, excellent transparency and satisfactory tensile strength. Our work provides a simple but efficient way to prepare UV-curable PSMA, which may find potential applications in UV-curing optical fiber, metal and glass coating and other fields.     

Unusual catalytic properties of nanostructured nickel films obtained by laser electrodispersion

Nanostructured nickel films deposited by laser electrodispersion onto a silicon (semiconducting) or thermally oxidized silicon (insulating) substrate show a remarkably high catalytic activity (of the order of 10³–10⁴ (mol product) (mol Ni)^?1 h^?1) in the isomerization of chlorinated hydrocarbons and olefin hydrogenation. The special properties of the laser-deposited films are likely due to the small size (2.5 nm), developed surface, and amorphism of the nickel particles, as well as to highly active, charged particles appearing on the insulating substrate. The latter result from thermal fluctuations of electrons between closely spaced particles. In a film deposited on silicon covered with a natural oxide layer, a significant role is also played by charge redistribution between the substrate and metal particles.     

Synthesis and properties of porous silica obtained by the template method

Micromesoporous samples of SiO₂ were synthesized by the sol-gel method using tetraethoxysilane as a starting reagent and 1–5 wt % cetylpyridinium chloride as a template under the conditions of preadsorption of colloid silica by polyethyleneglycol macromolecules. The adsorption and texture of the samples were studied by the low-temperature nitrogen adsorption-desorption technique. Preadsorption of silica sol was shown to affect the adsorption and capillary-condensation properties of silica. The surface area and the volume of mesopores increased at cetylpyridinium concentrations higher than 1 wt %. The micropore volume increased to a maximum. The capillary-condensation hysteresis loop of H4 type transformed into an H3 loop according to the IUPAC classification.     

A series of isostructural mesoporous metal-organic frameworks obtained by ion-exchange induced single-crystal to single-crystal transformation

A series of metal-organic frameworks representing a non-interpenetrated framework analogue of MOF-14 have been synthesized by using two different linkers, 4,4',4'-benzene-1,3,5-triyl-benzoic acid (H(3)BTB) and 4,4'-bipyridine (Bpy). Interestingly, the transition metal ions in the paddle-wheel metal clusters could be exchanged by other transition metal ions via a direct single-crystal to single-crystal transformation. This post-synthesis route can be used for synthesis of isomorphous metal-organic frameworks that cannot be obtained by direct synthesis.     

Optical and mechanical properties of films obtained by plasma decomposition of hexamethyldisilazane

Films of SiC _x N _y H _z composition are obtained by chemical deposition from the vapor phase via the activation of high-frequency discharge plasma (PECVD). The organosilicon compound hexamethyldisilazane, which contains all the atoms needed for the formation of films, is used as our initial material. Physicochemical properties of the films are studied by spectroscopy of surface acoustic waves, measuring the bending of a film-substrate system, ellipsometry, and infrared spectroscopy. Important features of the films?? structure are established. It is shown that at temperatures of deposition below 400°C, films contain chemical bonds of an organic nature, have very low values of density and the Young modulus, and exhibit high levels of elasticity, indicating their polymer-like structure. It is established that at higher temperatures of deposition, films are inorganic composite materials.     

Adhesion properties of poly(hexamethylene diisocyanate) obtained by organotin catalysis

Various organotin compounds were examined as catalysts for the polymerization of hexamethylene diisocyanate (HMDI) for use as an adhesive; (Bu₃Sn)₂O and Bu₂Sn(OCH₃)₂ gave the best results. The lap shear strength of poly(HMDI) with aluminium was 19.9 MPa; with Cab-O-Sil as a filter, it was 27.2 MPa. These values are comparable to those for epoxy adhesives.     

Physicomechanical properties of grafted polymers obtained by radiation-induced polymerization by radical and ionic mechanisms

The radiation-induced grafting of acrylonitrile, 4-vinylpyridine, and styrene was carried out by both radical and ionic mechanisms. Grafted polymers with equal percentages of graft were obtained by the radical and ionic propagation of the grafted chains. The molecular weight of homopolymers has been determined. The thermomechanical properties of the graft polymers were investigated. The yield temperatures for the graft polymers obtained by ionic propagation of the grafted chains is higher than that of graft polymers obtained by a radical mechanism. This is attributed to the higher molecular weight of the grafted chains obtained by the radiation-induced grafting by the ionic mechanism. The radiation-induced grafting of polyacrylonitrile increases significantly the thermal stability of polyethylene. The differential thermal analysis shows no marked differences in properties of the polymers.     

The electrical properties of chemically obtained barium titanate improved by attrition milling

Barium titanate ceramics were prepared using the nanopowder resulting from a polymeric precursor method, a type of modified Pechini process. The obtained nanopowder was observed to agglomerate and in order to de-agglomerate the powder and enhance the properties of the barium titanate the material was attrition milled. The impact of this attrition milling on the electrical properties of the barium titanate was analysed. The temperature dependence of the relative dielectric permittivity showed three structural phase transitions that are characteristic for ferroelectric barium titanate ceramics. The relative dielectric permittivity at the Curie temperature was higher for the attrition-treated sample than for the non-treated barium titanate. The dielectric losses were below 0.04 in both barium titanate ceramics. The grain and grain-boundary contributions to the total resistivity were observed using impedance analyses for both ceramics. A well-defined ferroelectric hysteresis loop and piezoelectric coefficient d₃₃ = 150 pC/N were obtained for the ceramics prepared from the de-agglomerated powder. In this way we were able to demonstrate that by attrition milling of chemically obtained powders the ferroelectric and piezoelectric properties of the ceramics could be enhanced.     

Phase transformation in a nanostructured M300 maraging steel obtained by SPS of mechanically alloyed powders

New complexes of type [Cu(HTBG)₂]Cl₂ (1), [Cu(TBG)₂]·3H₂O (2) and [CuL]·nH₂O (3) L:L¹, n = 2 and (4) L:L², n = 1 (HTBG: 2-tolylbiguanide, L¹ and L²: ligands resulted from 2-tolylbiguanide, ammonia/hydrazine and formaldehyde one pot condensation) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR and UV–Vis data. Redox behaviour was established by cyclic voltammetry. The in vitro qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity against Gram-negative and Gram-positive strains isolated from the hospital environment. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. After water elimination, complexes have a similar thermal behaviour. Processes as water elimination, melting, chloride anion removal as well as oxidative degradation of the organic ligands were observed. The final product of decomposition was copper (II) oxide.     

Specific oxidation of C-14 oxygenated 4(20),11-taxadienes by microbial transformation

Three C-14 oxygenated taxanes, 2α,5α,10β,14β-tetraacetoxytaxa-4(20),11-diene (1), 2α,5α,10β-triacetoxy-14β-(2-methylbutyryloxy)taxa-4(20),11-diene (2), and yunanaxane (3), major products of callus cultures of Taxus spp., were regio- and stereoselectively hydroxylated at the 7β position by a fungus, Absidia coerulea IFO 4011. Intriguingly, when 1 was co-administered with β-cyclodextrin and incubated with the fungus cell cultures, three other compounds 5α,9α,10β,13α-tetraacetoxytaxa-4(20),11-dien-14β-ol (7), 5α,9α,10β,13α-tetraacetoxytaxa-4(20),11-dien-1β-ol (8) and 5α,9α,10β,13α-tetraacetoxy-11(15→1) abeotaxa-4(20),11-dien-15-ol (9) were obtained.