Search results for "Hydrolysi"
showing 10 items of 635 documents
Lignin-based activated carbon-supported metal oxide catalysts in lactic acid production from glucose
2021
Abstract In this study, heterogeneous biomass-based activated carbon-supported metal oxide catalysts were prepared and tested for lactic acid production from glucose in aqueous solution. Activated carbons were produced from hydrolysis lignin by chemical (ZnCl2) or steam activation and modified with a nitric acid treatment and Sn, Al, and Cr chlorides to obtain carbon-based metal oxide catalysts. The modification of the carbon support by nitric acid treatment together with Sn and Al oxides led to an increase in lactic acid yield. The highest lactic acid yield (42 %) was obtained after 20 min at 180 °C with the Sn/Al (5/2.5 wt.%) catalyst on steam-activated carbon treated by nitric acid. Reus…
Prolin-benzylester als chirale Hilfsgruppen in asymmetrischen 1,3-dipolaren Cycloadditionen mit Nitriloxiden
1990
Proline Benzyl Esters as Chiral Auxiliaries in Asymmetric 1,3-Dipolar Cycloadditions N-Acryloylproline benzyl ester (1b) reacts with nitrile oxides at temperatures from −78 to 0°C to give isoxazolines 4/5 with diastereomeric ratios of ca. 3:1 and with the (5S) isomer as the predominating. The corresponding N-methacryloylproline benzyl ester (1c) gives inferior results. The diastereoselectivity is not influenced by the temperature and the substituents of the nitrile oxides. To prove the absolute configuration of the predominating stereoisomer, a reaction sequence is developed which makes use of an enantioselective hydrolysis with pig liver esterase as the key step to generate an optically ac…
A kinetic study of the basic hydrolysis of 2-phenylethyl nitrite in the presence of borate buffer and β-cyclodextrin
2002
The kinetics of the hydrolysis of 2-phenylethyl nitrite have been studied in basic aqueous solutions (borate buffer) in the absence and presence of β-cyclodextrin. The observed kinetic trends show that the hydrolysis reaction consists of at least three subsequent processes. The first is a fast acid-base reaction between the boron atom of boric acid and oxygen atom of the alkyl nitrite. The second one should be the nucleophilic attack of hydroxyl ion on the alkyl nitrite. The last process could be referred to as a combination of transfer of hydrogen acid to a water molecule followed by ruptures of nitrogen-oxygen and boron-oxygen bonds. The effect of β- cyclodextrin on each process is also d…
Reaction of 2-acetyltetralone with some esters of benzoic acid
1986
In order to investigate the pharmacological screening of a number of pyran-4-ones their synthesis by cyclization with sulphuric acid of the corresponding 1,3,5-triketones has been carried out with high yields. In the course of preparation of the latter the reaction of 2-acetyltetralone with some esters of benzoic acid derivatives has been studied and in particular, for a number of them, an interesting nucleophilic substitution of a chlorine atom with an alkoxy group on a benzenic nucleus has been evidenced.
Effects of Briquetting and High Pyrolysis Temperature on Hydrolysis Lignin Char Properties and Reactivity in CO-CO2-N2 Conditions
2021
Carbonaceous reductants for pyrometallurgical applications are usually obtained from fossil-based sources. The most important properties of the reductants greatly depend on the application and the feeding of the reductant into the process. However, the mechanical strength, calorific value, fixed carbon content, and reactivity of the reductant are the properties that usually define the applicability of the reductant for different processes. The reactivity of the biochars is usually high in comparison to metallurgical coke, which may restrict the applicability of the biochar in reduction processes. One cause of the higher reactivity is the higher surface area of the biochars, which can be sup…
Ruta chalepensis L. (Rutaceae) leaf extract: chemical composition, antioxidant and hypoglicaemic activities.
2017
Ruta chalepensis L. (Rutaceae) leaf extract was investigated for its chemical profile and antioxidant and hypoglycaemic properties. The antioxidant effects were investigated by 2,2-diphenyl-1-picrylhydrazyl (DPPH), Chi-carotene bleaching, and metal chelating activity assays. The carbohydrate-hydrolysing enzymes inhibition assay was used to test the hypoglycaemic potential. R. chalepensis showed a high content of hesperidin and rutin with values of 591.9 and 266.7 mg/g dry extract, respectively. The extract exhibited a promising protection of lipid peroxidation (IC50 value of 16.9 mu g/mL) and inhibited both alpha-amylase and alpha-glucosidase enzymes in a concentration-dependent manner. The…
Structure, Biosynthesis, and Bioactivity of Photoditritide from Photorhabdus temperata Meg1
2019
A new cyclic peptide photoditritide (1), containing two rare amino acid d-homoarginine residues, was isolated from Photorhabdus temperata Meg1 after the nonribosomal peptide synthetase encoding gene pdtS was activated via promoter exchange. The structure of 1 was elucidated by HR-MS and NMR experiments. The absolute configurations of amino acids were determined according to the advanced Marfey's method after hydrolysis of 1. Bioactivity testing of 1 revealed potent antimicrobial activity against Micrococcus luteus with an MIC value of 3.0 μM and weak antiprotozoal activity against Trypanosoma brucei rhodesiense with an IC50 value of 13 μM. Additionally, the biosynthetic pathway of 1 was als…
Intracellular acidosis in murine fibrosarcomas coincides with ATP depletion, hypoxia, and high levels of lactate and total Pi
1994
Bioenergetic and metabolic status of murine FSaII tumours were evaluated using 31P MRS, acid extracts ('global' techniques) and quantitative bioluminescence ('microregional' assay). Data obtained from s.c. tumours of varying sizes (44-600 mm3) have been correlated with the oxygenation status evaluated using O2-sensitive needle electrodes. beta-NTP/Pi and phosphocreatine (PCr)/Pi ratios derived from 31P MRS were positively correlated to the median tissue pO2 values. pH declined during growth with intracellular acidosis being evident in tumours > 350 mm3. Whereas lactic acid formation greatly contributed to this decline in small- and medium-sized tumours, ATP hydrolysis and slowing down of th…
Effect of coronary perfusion rate on the hydrolysis of exogenous and endogenous acetylcholine in the isolated heart
1977
1. The effect of perfusion rate on the hydrolysis of acetylcholine in isolated chicken hearts was studied by measuring both the spontaneous and the evoked output of endogenous acetylcholine into the perfusate in response to vagal stimulation and the arterio-venous difference of exogenous acetylcholine. 2. A decrease in the perfusion rate from 30 to 20 and 10 ml/min caused a graded and significant decline of both the spontaneous overflow of acetylcholine and the overflow evoked by stimulation of both vagus nerves (20 Hz, 1 ms, 40V) for 20 min. The spontaneous and evoked overflow at 30 ml/min were 2 and 3 times, respectively, the overflow at 10 ml/min. 3. Physostigmine (10−6M) raised both the…
Interstitial washout and hydrolysis of acetylcholine in the perfused heart
1982
The efflux of acetylcholine, of radioactively labelled acetylcholine and choline, into the venous effluent of the perfused chicken heart was studied to determine the kinetics of both interstitial washout and hydrolysis of acetylcholine. Stimulation of both cervical vagus nerves (e.g., for 5 s at 40 Hz) caused a release of acetylcholine, which appeared partially unhydrolyzed in the venous effluent, and reduced force of contraction and heart rate. For comparison, labelled acetylcholine or choline was infused for 5 s into the heart and again the venous efflux of either substance was determined. It was found that the kinetics of efflux of acetylcholine or choline from the interstitial space wer…