Multi-chain action of exo-D-galacturonanase from carrot

1983 ◽  
Vol 48 (12) ◽  
pp. 3579-3588
Author(s):  
Kveta Heinrichová ◽  
Jana Perečková
Keyword(s):  
Optimal Condition ◽  
Degradation Products ◽  
Degradation Kinetics ◽  
Hydrolytic Cleavage ◽  
Chain Mechanism ◽  
Modes Of Action ◽  
Enzyme Degradation ◽  
Good Agreement

Two possible modes of action of exo-D-galacturonanase from carrot (E.C. 3.2.1.67) were investigated; this enzyme catalyses the sequential hydrolytic cleavage of pectants and oligogalacturonans by a terminal action from the nonreducing end of the molecule. The experiments indicate that the investigated exo-D-galacturonanase degrades these substrates by a predominantly multi-chain mechanism. Distribution of degradation products of oligomeric substrates (hexa- and pentagalacturonide) under an optimal condition for the action of the enzyme (pH and temperature) indicates that a multi-chain enzyme attack with a prevalent simple collision is involved. Results of the enzyme degradation kinetics are in a good agreement with the above-mentioned presumption.

scholarly journals The in vitro assessment of the toxicity of volatile, oxidisable, redox-cycling compounds: phenols as an example

2021 ◽  
Author(s):  
Laia Tolosa ◽  
Teresa Martínez-Sena ◽  
Johannes P. Schimming ◽  
Erika Moro ◽  
Sylvia E. Escher ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Degradation Products ◽  
Degradation Kinetics ◽  
Redox Cycling ◽  
In Vitro Toxicity ◽  
Cross Contamination ◽  
Physicochemical Changes ◽  
In Vitro Assessment ◽  
Biological Performance

AbstractPhenols are regarded as highly toxic chemicals. Their effects are difficult to study in in vitro systems because of their ambiguous fate (degradation, auto-oxidation and volatility). In the course of in vitro studies of a series of redox-cycling phenols, we found evidences of cross-contamination in several in vitro high-throughput test systems, in particular by trimethylbenzene-1, 4-diol/trimethylhydroquinone (TMHQ) and 2,6-di-tertbutyl-4-ethylphenol (DTBEP), and investigated in detail the physicochemical basis for such phenomenon and how to prevent it. TMHQ has fast degradation kinetics followed by significant diffusion rates of the resulting quinone to adjacent wells, other degradation products being able to air-diffuse as well. DTBEP showed lower degradation kinetics, but a higher diffusion rate. In both cases the in vitro toxicity was underestimated because of a decrease in concentration, in addition to cross-contamination to neighbouring wells. We identified four degradation products for TMHQ and five for DTBEP indicating that the current effects measured on cells are not only attributable to the parent phenolic compound. To overcome these drawbacks, we investigated in detail the physicochemical changes occurring in the course of the incubation and made use of gas-permeable and non-permeable plastic seals to prevent it. Diffusion was greatly prevented by the use of both plastic seals, as revealed by GC–MS analysis. Gas non-permeable plastic seals, reduced to a minimum compounds diffusion as well oxidation and did not affect the biological performance of cultured cells. Hence, no toxicological cross-contamination was observed in neighbouring wells, thus allowing a more reliable in vitro assessment of phenol-induced toxicity.

scholarly journals Advanced Oxidation Process for Degradation of Carbamazepine from Aqueous Solution: Influence of Metal Modified Microporous, Mesoporous Catalysts on the Ozonation Process

Catalysts ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 90 ◽  
Author(s):  
Soudabeh Saeid ◽  
Matilda Kråkström ◽  
Pasi Tolvanen ◽  
Narendra Kumar ◽  
Kari Eränen ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Advanced Oxidation Process ◽  
Degradation Products ◽  
Degradation Kinetics ◽  
Removal Rate ◽  
Influence Of Temperature On ◽  
Two Temperatures ◽  
Kinetics Of ◽  
Ozonation Process ◽  
Mcm 41

Carbamazepine (CBZ), a widely used pharmaceutical compound, is one of the most detected drugs in surface waters. The purpose of this work was to identify an active and durable catalyst, which, in combination with an ozonation process, could be used to remove CBZ and its degradation products. It was found that the CBZ was completely transformed after ozonation within the first minutes of the treatment. However, the resulting degradation products, 1-(2-benzaldehyde)-4-hydro-(1H,3H)-quinazoline-2-one (BQM) and 1-(2-benzaldehyde)-(1H,3H)-quinazoline-2,4-dione (BQD), were more resistant during the ozonation process. The formation and degradation of these products were studied in more detail and a thorough catalytic screening was conducted to reveal the reaction kinetics of both the CBZ and its degradation products. The work was performed by non-catalytic ozonation and with six different heterogeneous catalysts (Pt-MCM-41-IS, Ru-MCM-41-IS, Pd-H-Y-12-EIM, Pt-H-Y-12-EIM, Pd-H-Beta-300-EIM and Cu-MCM-41-A-EIM) operating at two temperatures 20 °C and 50 °C. The influence of temperature on degradation kinetics of CBZ, BQM and BQD was studied. The results exhibited a notable difference in the catalytic behavior by varying temperature. The higher reactor temperature (50 °C) showed a higher activity of the catalysts but a lower concentration of dissolved ozone. Most of the catalysts exhibited higher removal rate for BQM and BQD compared to non-catalytic experiments in both temperatures. The Pd-H-Y-12-EIM catalyst illustrated a higher degradation rate of by-products at 50 °C compared to other catalysts.

Development and Validation of Stability Indicating High-Performance Thin-Layer Chromatographic (HPTLC) Method for Quantification of Asiaticoside from Centella asiatica L. and its Marketed Formulation

2019 ◽  
Vol 102 (4) ◽  
pp. 1014-1020
Author(s):  
Lisa J Patel ◽  
Manan A Raval ◽  
Samir G Patel ◽  
Archita J Patel
Keyword(s):  
High Performance ◽  
Degradation Products ◽  
Degradation Kinetics ◽  
Centella Asiatica ◽  
Stability Study ◽  
Cns Disorders ◽  
Marker Compound ◽  
Plant Powders ◽  
Development And Validation ◽  
Hptlc Method

Abstract Background: Ayurvedic medicines help in healing disease with fewer undesirable effects in comparison with an allopathic system of medicine to treat central nervous system (CNS) disorders, as the latter is more expensive. Centella asiatica L. is often used in Ayurvedic formulations for the treatment of CNS disorders. Objective: A stability test using an HPTLC method for the estimation of an important marker asiaticoside (ASI) from C. asiatica powder and marketed formulation was developed. Methods: The marker compound ASI from plant powders and marketed formulations were resolved using toluene–ethyl acetate–methanol–glacial acetic acid (2+7+3+1, v/v/v/v) as the mobile phase and then was derivatized. The plant powder and marketed formulation were also subjected to stability studies. Results: The Rf value of ASI was found in range of 0.43–0.47 for the standard ASI, plant powder, and marketed formulation. It was found that the plant powder and formulation exhibited first-order degradation kinetics. Conclusions: The contents of ASI in the formulation (Churna) and its flow characters reduced at the end of the 6 months during an accelerated stability study. The developed method can be used to quantify ASI in the presence of its degradation products. Highlights: The developed method helps in determining batch to batch variation in the content of ASI in herbal formulations.

scholarly journals Understanding and Kinetic Modeling of Complex Degradation Pathways in the Solid Dosage Form: The Case of Saxagliptin

Pharmaceutics ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 452 ◽  
Author(s):  
Robnik ◽  
Likozar ◽  
Wang ◽  
Stanić Ljubin ◽  
Časar
Keyword(s):  
Relative Humidity ◽  
Degradation Product ◽  
Degradation Products ◽  
Drug Product ◽  
Degradation Kinetics ◽  
Dosage Forms ◽  
Drug Substance ◽  
Polymer Composition ◽  
Solid Dosage Forms ◽  
Solid Dosage

Drug substance degradation kinetics in solid dosage forms is rarely mechanistically modeled due to several potential micro-environmental and manufacturing related effects that need to be integrated into rate laws. The aim of our work was to construct a model capable of predicting individual degradation product concentrations, taking into account also formulation composition parameters. A comprehensive study was done on active film-coated tablets, manufactured by layering of the drug substance, a primary amine compound saxagliptin, onto inert tablet cores. Formulation variables like polyethylene glycol (PEG) 6000 amount and film-coat polymer composition are incorporated into the model, and are connected to saxagliptin degradation, via formation of reactive impurities. Derived reaction equations are based on mechanisms supported by ab initio calculations of individual reaction activation energies. Alongside temperature, relative humidity, and reactant concentration, the drug substance impurity profile is dependent on micro-environmental pH, altered by formation of acidic PEG degradation products. A consequence of pH lowering, due to formation of formic acid, is lower formation of main saxagliptin degradation product epi-cyclic amidine, a better resistance of formulation to high relative humidity conditions, and satisfactory tablet appearance. Discovered insights enhance the understanding of degradational behavior of similarly composed solid dosage forms on overall drug product quality and may be adopted by pharmaceutical scientists for the design of a stable formulation.

Eco-Friendly Green Liquid Chromatographic Determination of Azelastine in the Presence of its Degradation Products: Applications to Degradation Kinetics

2019 ◽  
Vol 102 (1) ◽  
pp. 81-90 ◽  
Author(s):  
Amal A El-Masry ◽  
Mohammed E A Hammouda ◽  
Dalia R El-Wasseef ◽  
Saadia M El-Ashry
Keyword(s):  
Degradation Products ◽  
Degradation Kinetics ◽  
Sodium Dodecyl ◽  
Internal Standard ◽  
Eye Drops ◽  
Control Analysis ◽  
Stability Indicating ◽  
Highly Sensitive ◽  
Antihistaminic Drug

Abstract Background: Green solvents such as microemulsion were used in the proposed method because they play a vital role in the analytical method’s influence on the environment. Objective: A highly sensitive, specific, and validated stability-indicating eco-friendly green microemulsion liquid chromatography (MELC) method was developed for separation of the antihistaminic drug Azelastine HCl (AZL) from its degradation products with application to degradation kinetics. Methods: Chromatographic separation was operated on a C18 column with a microemulsion mobile phase, which consists of 0.1 M sodium dodecyl sulphate, 10% n-propanol, 1% n-octanol, and 0.3% triethylamine, by using 0.02 M phosphoric acid at pH 3.5 and irbesartan as internal standard. The eluted compounds were monitored at 210 nm with flow rate 1 mL/min at ambient temperature. Results: A linear dependence of the peak area on drug concentration over the concentration range of 0.1 to 25 μg/mL was achieved with an LOD of 0.04 μg/mL and an LOQ of 0.10 μg/mL. Moreover, the proposed method was successfully applied for determination of AZL in eye drops and metered dose nasal inhaler as well as to study the kinetics of alkaline, acidic, neutral, oxidative, and photolytic degradation processes of AZL according to the International Council for Harmonization guidelines. Conclusions: The proposed method could be used as a harmless alternative for quality control analysis of the mentioned drug, without interference from dosage form additives or decomposition products. Highlights: A highly sensitive stability-indicating eco-friendly green MELC method was developed for the separation of the antihistaminic drug AZL from its degradation products.

Prediction of Detonation Pressure of Aluminized Explosive by Artificial Neural Network

2013 ◽  
Vol 641-642 ◽  
pp. 460-463
Author(s):  
Yong Gang Liu ◽  
Xin Tian ◽  
Yue Qiang Jiang ◽  
Gong Bing Li ◽  
Yi Zhou Li
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Optimal Condition ◽  
Detonation Pressure ◽  
Ann Model ◽  
Training Set ◽  
The Neural Network ◽  
Artificial Neural ◽  
Artificial Neural Network Ann ◽  
Good Agreement

In this study, a three-layer artificial neural network(ANN) model was constructed to predict the detonation pressure of aluminized explosive. Elemental composition and loading density were employed as input descriptors and detonation pressure was used as output. The dataset of 41 aluminized explosives was randomly divided into a training set (30) and a prediction set (11). After optimized by adjusting various parameters, the optimal condition of the neural network was obtained. Simulated with the final optimum neural network [6–9–1], calculated detonation pressures show good agreement with experimental results. It is shown here that ANN is able to produce accurate predictions of the detonation pressure of aluminized explosive.

scholarly journals Electrochemical degradation of diclofenac by boron doped diamond anode: degradation mechanism, pathways and influencing factors

2021 ◽  
Author(s):  
Huimin Qiu ◽  
Pingping Fan ◽  
Xueying Li ◽  
Guangli Hou
Keyword(s):  
Influencing Factors ◽  
Wastewater Treatment Plants ◽  
Degradation Products ◽  
Degradation Kinetics ◽  
Degradation Mechanism ◽  
Electrochemical Process ◽  
Sodium Sulphate ◽  
Boron Doped Diamond ◽  
Quenching Effect ◽  
Boron Doped

Abstract Nonsteroidal anti-inflammatory drugs (NAIDS) have been widely detected in wastewater and surface water, which indicates the removal of NAIDS by wastewater treatment plants was not efficiency. Electrochemical advanced oxidation technology is considered to be an effective process. This study presents an investigation of the kinetics, mechanism and influencing factors of Diclofenac (DCF) degradation by an electrochemical process with the boron doped diamond anodes. Relative operating parameters and water quality parameters are examined. It appears that the degradation follows the pseudo-first-order degradation kinetics. DCF degradation was accelerated with the increase of pH from 6 to 10. The degradation was promoted by the addition of electrolyte concentrations and current density. HA and HCO3− significantly inhibited the degradation, whereas Cl− accelerated it. According to the inhibition tests, hydroxyl radicals (•OH) and sulfate radicals (SO4•–) contributed 76.5% and 6.5%, respectively, to the degradation. Sodium sulphate remains a more effective electrolyte, compared to sodium nitrate and sodium phosphate, suggesting the quenching effect of nitrate and phosphate on •OH. Major DCF transformation products were identified. According to the degradation products detected by liquid chromatography-mass spectrometry, hydroxylation and decarboxylation are the main pathways to DCF degradation; meanwhile, dechlorination, chlorination and nitro substitution are also included.

scholarly journals Enhanced Cypermethrin Degradation Kinetics and Metabolic Pathway in Bacillus thuringiensis Strain SG4

2020 ◽  
Vol 8 (2) ◽  
pp. 223 ◽  
Author(s):  
Pankaj Bhatt ◽  
Yaohua Huang ◽  
Wenping Zhang ◽  
Anita Sharma ◽  
Shaohua Chen
Keyword(s):  
Bacillus Thuringiensis ◽  
Metabolic Pathway ◽  
Large Scale ◽  
Degradation Products ◽  
Degradation Kinetics ◽  
Active Role ◽  
Minimal Salt Medium ◽  
Bacterial Strains ◽  
Soil Slurry ◽  
Thuringiensis Strain

Cypermethrin is popularly used as an insecticide in households and agricultural fields, resulting in serious environmental contamination. Rapid and effective techniques that minimize or remove insecticidal residues from the environment are urgently required. However, the currently available cypermethrin-degrading bacterial strains are suboptimal. We aimed to characterize the kinetics and metabolic pathway of highly efficient cypermethrin-degrading Bacillus thuringiensis strain SG4. Strain SG4 effectively degraded cypermethrin under different conditions. The maximum degradation was observed at 32 °C, pH 7.0, and a shaking speed of 110 rpm, and about 80% of the initial dose of cypermethrin (50 mg·L−1) was degraded in minimal salt medium within 15 days. SG4 cells immobilized with sodium alginate provided a higher degradation rate (85.0%) and lower half-life (t1/2) of 5.3 days compared to the 52.9 days of the control. Bioaugmentation of cypermethrin-contaminated soil slurry with strain SG4 significantly enhanced its biodegradation (83.3%). Analysis of the degradation products led to identification of nine metabolites of cypermethrin, which revealed that cypermethrin could be degraded first by cleavage of its ester bond, followed by degradation of the benzene ring, and subsequent metabolism. A new degradation pathway for cypermethrin was proposed based on analysis of the metabolites. We investigated the active role of B. thuringiensis strain SG4 in cypermethrin degradation under various conditions that could be applied in large-scale pollutant treatment.

Sonochemical decomposition of phenol: evidence for a synergistic effect of ozone and ultrasound for the elimination of total organic carbon

2006 ◽  
Vol 6 (3) ◽  
pp. 71-78
Author(s):  
T. Lesko ◽  
A.J. Colussi ◽  
M.R. Hoffmann
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Degradation Products ◽  
Degradation Kinetics ◽  
Synergistic Effects ◽  
Phenol Degradation ◽  
Ultrasonic Power ◽  
Intermediate Species ◽  
Oxidation Processes ◽  
The Individual

The degradation of phenol (C6H5OH) was investigated under sonication, ozonation, and the combination of sonication and ozonation. The coupling of these two oxidation processes yielded phenol degradation kinetics that are similar to those predicted from the linear combination of the individual sonication and ozonation experiments. However, synergistic effects of sonolytic ozonation were observed for the reduction of the total organic carbon (TOC) in these systems. The rate of TOC decomposition was found to be proportional to both the aqueous steady-state ozone concentration and the ultrasonic power density. At 358 kHz, sonication combined with ozonation enhanced TOC loss rates by 43% over the sum of the rates obtained by the separate treatments. Intermediate species detected during the degradation of phenol indicate that while the primary degradation products are efficiently degraded by simple ozonolysis, the simultaneous addition of ultrasonic irradiation is necessary to degrade the more recalcitrant unsaturated daughter products.

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