The interactions between lipase and pyridinium ligands investigated by electrochemical and spectrophotometric methods

The interaction between pyridinium ligands derived from 4,4’-bipyridine (N,N’-bis(p-bro-mophenacyl)-4,4’-bipyridinium dibromide – Lr) and (N,N’-bis(p-bromophenacyl)-1,2-bis (4-pyridyl) ethane dibromide – Lm) with lipase enzyme was evaluated. The stability of the pyridinium ligands, having an essential role in biological systems, in 0.1 M KNO3 as supporting electrolyte is influenced by the lipase concentration added. The pH and conductometry measurements in aqueous solution suggest a rapid ionic exchange process. The behavior of pyridinium ligands in the presence of lipase is investigated by cyclic voltammetry and UV/Vis spectroscopy, which indicated bindings and changes from the interaction between them. The voltammograms recorded on the glassy carbon elec-trode showed a more intense electronic transfer for the Lr interaction with lipase com-pared to Lm, which is due to the absence of mobile ethylene groups from Lr structure

Catalytic Effect of Photoluminescent Zinc Oxide Nanoparticles Formed in the Presence of Quaternary Ammonium Salts

The comparative effect of two quaternary ammonium salts from 1,2-bis(4-pyridyl)ethane (PyQAs), namely N,N′-diphenacyl-1,2-bis(4-pyridinium)ethane dibromide (PyQAs1) and N,N′-di(p-methoxyphenacyl)-1,2-bis(4-pyridinium)ethane dibromide (PyQAs2), upon the size and photoluminescence of zinc oxide nanoparticles (ZnO NPs) was investigated. The formation of ZnO NPs took place in the presence of variable amounts of the two PyQAs species (1, 2.5, and 5%), according to the chemical precipitation of zinc(II) acetate with potassium hydroxide in ethanol under reflux. The obtained ZnO NPs were structurally characterized by means of X-ray powder diffraction, infrared, and Raman spectroscopy. The fluorescence of all supernatant solutions, observed under ultraviolet light, determined us to make an investigation of the solutions by means of liquid chromatography coupled with electrospray ionization mass spectrometry (LC-MS-ESI) in order to elucidate the identity of the newly formed fluorescent species. Such an occurrence thus allowed the invocation of the catalytic effect of zinc(II) ions towards the organic transformation of both nonfluorescent PyQAs surfactants into new fluorescent organic species

Extraction and evaluation of bioactive compounds with antioxidant potential from green arabica coffee extract

During the last decade researches concerning the essential role of coffee in health and disease prevention showed an increased development. In the present study we obtained extracts from three green Arabica coffee varieties which demonstrated a significant antioxidant potential due to the presence in their composition of two bioactive compounds, caffeine and chlorogenic acids. The content and antioxidant activity of bioactive compounds were evaluated by qualitative and quantitative analyses using spectrophotometric and chromatography methods. The chlorogenic acid was found in high concentrations, being followed by gallic, p-coumaric and ferulic acids. The highest caffeine contents were found in the green coffee extracts of the Supremo–Columbia and Top Quality–Kenya products

Antioxidative activity and stability of the extracts of liquorice root (Glycyrrhiza glabra)

The active principles from the aqueous liquorice plant extracts were investigated and quantified by evaluation of bioactive compounds (saponins) through phytochemical reactions. The presence of saponins was evaluated by measuring the foam index, which was around 500. A major component was Glycyrrhizic acid, responsible for the antioxidant activity, found in concentration of 5.82 % at plant maturity. A time-dependent decrease in concentration of the bioactive compounds from aqueous liquorice extracts was observed. The antimicrobial activity of the extracts was tested by the agar diffusion method, showing a moderate inhibitory activity against Bacillus sp. and strong inhibitory activity against coliforms. A liquorice syrup was obtained and subsequently could be used as nutraceutical additive in bread with good results, showing characteristic, optical and antimicrobial properties and good stability in time. Adding liquorice syrup in food products could be an alternative to improve nutraceutical potential

Insights on Monosaccharides and Bioethanol Production from Sweet Sorghum Stalks Using Dilute Acid Pretreatment

Sweet sorghum is a unique bioenergy crop that produces stalks with fermentable free sugars. The purpose of this study was to evaluate how the production of hemicellulosic saccharides and bioethanol from sweet sorghum stalks (SSS) can be influenced by a dilute sulfuric acid (H2SO4) pretreatment under different isothermal conditions. The bioethanol production from untreated SSS and pretreated solid phases was achieved through the Simultaneous Saccharification and Fermentation (SSF) process. A good SSS fractionation and an extensive hemicellulose hydrolysis into soluble saccharides were obtained, the most abundant hemicellulose-derived compounds present in the pretreated liquid phase being monosaccharides, with up to 17.22 g/L of glucose and 16.64 g/L of xylose in the pretreatments performed with 3% and 1% H2SO4 for 30 min at 134 °C, respectively. The SSF process of untreated SSS allowed a maximum bioethanol concentration of 9.78 g/L, corresponding to a maximum glucan conversion into ethanol of 49.8%. Bioethanol production from untreated SSS led to a higher bioethanol concentration and conversion than in the case of using acid pretreated solid phases obtained under the most severe conditions (with 3% H2SO4 for 30, 60 and 120 min at 134 °C), suggesting that, in the case of this biomass naturally rich in soluble sugars, the acidic pretreatment could negatively influence the fermentative process