scholarly journals Comparative Stability of Two Anti-Hyperpigmentation Agents: Kojic Acid as a Natural Metabolite and Its Di-Palmitate Ester, Under Oxidative Stress; Application to Pharmaceutical Formulation Design

2021 ◽  
Author(s):  
Sahar Tazesh ◽  
Elnaz Tamizi ◽  
Mohammadreza Siahi Shadbad ◽  
Nazli Mostaghimi ◽  
Farnaz Monajjemzadeh
Keyword(s):  
Oxidative Stress ◽  
Kojic Acid ◽  
Stress Test ◽  
Pharmaceutical Preparation ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Degradation Model ◽  
Internal Phase ◽  
Comparative Stability ◽  
Natural Metabolite

Purpose: Kojic acid a natural metabolite (KA) and its dipalmitate ester, kojic acid dipalmitate (Kadp) are both prescribed to treat skin hyperpigmentation. Stress test reveals the intrinsic stability of active ingredients and leads to selection of the suitable formulations. This research evaluates the comparative stability of KA and its di-palmitate ester under liquid oxidative stress. Methods: The HPLC-UV/PDA method with a C18 column was utilized. Liquid oxidative stress was induced using hydrogen peroxide (H2O2). Degradation was separately induced for each drug, and they were compared to each other. Results: Kadp degraded more rapidly in similar liquid oxidative stress conditions than KA did. The superior degradation model was the first order for both drugs based on the MPE values, indicating the dependency of the reaction rate on the initial concentration of the reactive substance. Ring opening was proposed as the most possible theory for KA and Kadp oxidative degradation. Conclusion: It is suggested to use KA instead of Kadp in less stable formulations, such as extemporaneous preparations. The incorporation of antioxidant excipients in Kadp formulations is recommended for yielding better stability results. Formulating Kadp in the internal phase of o/w emulsion formulations may protect this susceptive molecule from oxidative degradation during the shelf life of the pharmaceutical preparation. Further studies are required to study the exact mechanism of the degradation process.

scholarly journals Heat Aged Tensile Strength Retention of Poly (p-phenylene terephthalamide) Sewing Thread

2008 ◽  
Vol 3 (4) ◽  
pp. 155892500800300 ◽  
Author(s):  
Walter R. Hall ◽  
Warren F. Knoff
Keyword(s):  
Hydrolytic Degradation ◽  
Oxidative Degradation ◽  
Thermal Exposure ◽  
Strength Loss ◽  
Degradation Process ◽  
Downstream Processing ◽  
Kink Bands ◽  
Sewing Thread ◽  
Continuous Filament ◽  
Strength Retention

The strength retention after exposure to elevated temperature in air of continuous filament and staple spun PPTA sewing thread and the precursor yarns was determined. For both types, the process of converting the greige yarn to thread reduced the amount of strength retained after thermal exposure. The continuous filament products retained more strength than the staple products. The data was fitted to a kinetic rate model in which two strength loss processes occurred. The first process occurred within about the first 5 minutes of thermal exposure and is hypothesized to be hydrolytic degradation. The estimated secondary degradation process activation energy suggests this to be thermo-oxidative degradation. Optical microscopy of filaments indicates a higher level of kink banding and other damage in continuous filament versus staple products and in finished thread versus the precursor yarns. The kink bands and damage are believed to be caused by the staple manufacturing process and the downstream processing of precursor yarn to finished sewing thread. The kink bands and damage are hypothesized to be responsible for the differences in strength retention.

scholarly journals Effect of char layer on transient thermal oxidative degradation of polyethylene

2007 ◽  
Vol 11 (2) ◽  
pp. 23-36 ◽  
Author(s):  
Javad Esfahani ◽  
Ali Abdolabadi
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Solid Phase ◽  
Early Stage ◽  
Radiation Heat Transfer ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Thermal Oxidative Degradation ◽  
Char Layer ◽  
Effect Of Oxygen

A transient one dimensional model has been presented to simulate degradation and gasification of polyethylene, in early stage of fire growth. In the present model effect of oxygen on degradation and rate of polymer gasification while the sample is subjected to an external radiative heat source is numerically investigated. This model includes different mechanism, which affect the degradation process, such as in depth thermal oxidative decomposition, in depth absorption of radiation, heat transfer, volatiles advection in solid phase and convective heat transfer on surface. Also effects of radiative parameters, due to formation of char layer such as surface reflectivity and absorptivity on thermal degradation of polyethylene are investigated. The results for 40 kW/m2 heat source are reported and yielded realistic results, comparing to the published experimental data. The results show that an increase in oxygen concentration leads to considerable increase in gasification rate and also leads to sharp increase of surface temperature. .

Corrosion Margins for Redundant Ship Structures

2018 ◽  
Author(s):  
Yordan Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Differential Equation ◽  
Degradation Process ◽  
Step Function ◽  
Order System ◽  
Safety Factors ◽  
Ship Structures ◽  
Degradation Model ◽  
Corrosion Depth ◽  
First Order ◽  
Partial Safety Factors

The work presented here analyses the structural corrosion degradation of two sets of corrosion depth measurements collected with a one-decade difference. The corrosion degradation process is associated to a first order system, subjected to a sudden disturbance, where a step function is used as an input to define the solution of the differential equation of this system leads to the exponential corrosion degradation model as developed earlier. Corrosion margins of redundant ship structures with serious consequences of failure are derived and several conclusions related to the new trend in the ageing structures are presented and discussed. Partial safety factors with respect to the corrosion environment and corrosion margins are developed that can be used in the design, avoiding a complex probabilistic analysis.

scholarly journals Isolation and Structure Determination of Echinochrome A Oxidative Degradation Products

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4778
Author(s):  
Natalia P. Mishchenko ◽  
Elena A. Vasileva ◽  
Andrey V. Gerasimenko ◽  
Valeriya P. Grigorchuk ◽  
Pavel S. Dmitrenok ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Degradation Products ◽  
Lethal Dose ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Ionization Mass ◽  
Echinochrome A ◽  
Esi Ms

Echinochrome A (Ech A, 1) is one of the main pigments of several sea urchin species and is registered in the Russian pharmacopeia as an active drug substance (Histochrome®), used in the fields of cardiology and ophthalmology. In this study, Ech A degradation products formed during oxidation by O2 in air-equilibrated aqueous solutions were identified, isolated, and structurally characterized. An HPLC method coupled with diode-array detection (DAD) and mass spectrometry (MS) was developed and validated to monitor the Ech A degradation process and identify the appearing compounds. Five primary oxidation products were detected and their structures were proposed on the basis of high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) as 7-ethyl-2,2,3,3,5,7,8-heptahydroxy-2,3-dihydro-1,4-naphthoquinone (2), 6-ethyl-5,7,8-trihydroxy-1,2,3,4-tetrahydronaphthalene-1,2,3,4-tetraone (3), 2,3-epoxy-7-ethyl-2,3-dihydro-2,3,5,6,8-pentahydroxy-1,4-naphthoquinone (4), 2,3,4,5,7-pentahydroxy-6-ethylinden-1-one (5), and 2,2,4,5,7-pentahydroxy-6-ethylindane-1,3-dione (6). Three novel oxidation products were isolated, and NMR and HR-ESI-MS methods were used to establish their structures as 4-ethyl-3,5,6-trihydroxy-2-oxalobenzoic acid (7), 4-ethyl-2-formyl-3,5,6-trihydroxybenzoic acid (8), and 4-ethyl-2,3,5-trihydroxybenzoic acid (9). The known compound 3-ethyl-2,5-dihydroxy-1,4-benzoquinone (10) was isolated along with products 7–9. Compound 7 turned out to be unstable; its anhydro derivative 11 was obtained in two crystal forms, the structure of which was elucidated using X-ray crystallography as 7-ethyl-5,6-dihydroxy-2,3-dioxo-2,3-dihydrobenzofuran-4-carboxylic acid and named echinolactone. The chemical mechanism of Ech A oxidative degradation is proposed. The in silico toxicity of Ech A and its degradation products 2 and 7–10 were predicted using the ProTox-II webserver. The predicted median lethal dose (LD50) value for product 2 was 221 mg/kg, and, for products 7–10, it appeared to be much lower (≥2000 mg/kg). For Ech A, the predicted toxicity and mutagenicity differed from our experimental data.

Neutral fabrication of UV-blocking and antioxidation lignin-stabilized high internal phase emulsion encapsulates for high efficient antibacterium of natural curcumin

2019 ◽  
Vol 10 (6) ◽  
pp. 3543-3555
Author(s):  
Kai Chen ◽  
Yong Qian ◽  
Senyi Wu ◽  
Xueqing Qiu ◽  
Dongjie Yang ◽  
...  
Keyword(s):  
Antibacterial Properties ◽  
Oxidative Degradation ◽  
High Internal Phase Emulsion ◽  
Uv Blocking ◽  
Internal Phase ◽  
High Efficient

Curcumin was encapsulated inside the sulfomethylated lignin stabilized HIPEs and exhibited superior UV and oxidative degradation resistance and antibacterial properties.

Evaluation of the Degradation Dynamics of Thin Silicon Dioxide Films Using Model-Independent Procedures

1999 ◽  
Vol 592 ◽  
Author(s):  
R. Rodríguez ◽  
M. Nafría ◽  
E. Miranda ◽  
J. Suñé ◽  
X. Aymerich
Keyword(s):  
Silicon Dioxide ◽  
Degradation Process ◽  
Quantitative Information ◽  
Constant Current ◽  
Degradation Model ◽  
Electrical Stress ◽  
Silicon Dioxide Films ◽  
Model Independent ◽  
Thin Silicon ◽  
Mean Time

ABSTRACTThe degradation and breakdown of thin silicon dioxide films has been analysed using a two-step stress method. This procedure allows the evaluation of the degradation induced by the electrical stress without any assumption about the microscopic nature of the degradation process. The method has been used to analyse and compare the degradation dynamics when constant-voltage (CVS) and constant-current stresses (CCS) are applied to the oxide. Moreover, it is shown that in the case of CVS, the fitting of the I-t characteristics can provide quantitative information about the degradation (degradation rate) and breakdown (mean-time-to-breakdown), without taking into account any degradation model.

Environmental Oxidative Degradation and Biodegradation of Eco-Benign Plastics

2013 ◽  
Vol 538 ◽  
pp. 146-149 ◽  
Author(s):  
Xin De Tang ◽  
Jing Lun Zhou ◽  
Hai Rong Lu ◽  
Nian Feng Han
Keyword(s):  
Structural Characteristics ◽  
Oxidative Degradation ◽  
Environmental Issues ◽  
Degradation Process ◽  
Linear Low Density Polyethylene ◽  
Soil Environment ◽  
Photo Degradation ◽  
Soil Burial ◽  
Ft Ir ◽  
Abiotic Oxidation

Polyethylene (PE) has found widespread use as a packaging material. Plastics waste disposal, as one of the serious environmental issues, has caused much criticism. The environmental oxidative- and bio- dual degradable linear low-density polyethylene (LLDPE) samples containing Eco-Benign Plastics (EBP) pro-oxidant additives were submitted to an investigation aimed at evaluating their preliminary oxidative degradation in natural environment or accelerated oven aging and their ultimate biodegradation in solid incubation substrate or soil composting conditions. Original and test samples submitted to abiotic oxidation including photo degradation and thermal degradation were characterized by means of FT-IR and GPC. Biodegradation test simulating soil burial and composting conditions reveals that the biodegradation degree exceeded 30%. The degradation process is accompanied by a dramatic change in the structural characteristics of the test samples. It is clear that LLDPE-EBP formulations are effective in promoting the oxidation and subsequent biodegradation of polyethylene in natural and soil environment.

An in vitro oxidative stress test for determining pollutant tolerance in algae

2006 ◽  
Vol 6 (4) ◽  
pp. 770-779 ◽  
Author(s):  
C. Johnstone ◽  
J.G. Day ◽  
H. Staines ◽  
E.E. Benson
Keyword(s):  
Oxidative Stress ◽  
Stress Test

scholarly journals Preliminary Feasibility Study of Benzo(a)Pyrene Oxidative Degradation by Fenton Treatment

2009 ◽  
Vol 2009 ◽  
pp. 1-6 ◽  
Author(s):  
Vera Homem ◽  
Zélia Dias ◽  
Lúcia Santos ◽  
Arminda Alves
Keyword(s):  
Removal Efficiency ◽  
Water Contamination ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Fenton Reagent ◽  
Laboratory Unit ◽  
Ion Concentrations ◽  
New Methods ◽  
Polycyclic Aromatic ◽  
Aqueous Matrices

Polycyclic aromatic hydrocarbons (PAHs) are considered priority compounds due to their toxic and carcinogenic nature. The concern about water contamination and the consequent human exposure has encouraged the development of new methods for PAHs removal. The purpose of this work was to study the feasibility of a degradation process of benzo(a)pyrene (BaP) in aqueous matrices by oxidation with Fenton reagent. A laboratory unit was designed to optimize the factors which may influence the process: pH (3.5 to 6.0), temperature (30 to70°C),H2O2(20 to 150 mgL-1),Fe2+concentration (2.75 to 5.50 mgL-1), and the initial concentration of the pollutant (10 to 100 μgL-1). The pH did not influence significantly the results in the range studied. An increase in temperature from 30 to70°Cimproved the removal efficiency from 90% to 100%. The same effect was observed for ferrous ion concentrations from 2.75 to 5.50 mgL-1(increase from 78% to 100% removal). TheH2O2concentration played a double role during the process: from 20 to 50 mgL-1an increase in the removal efficiency was achieved, but for higher concentrations (>50 mgL-1) the degradation is lower. This study proved that the degradation of benzo(a)pyrene by Fenton's reagent is a viable process.

scholarly journals The possibilities of pharmacological correction of ademol oxidative stress in rates with traumatic brain injury

2021 ◽  
Vol 25 (2) ◽  
pp. 192-195
Author(s):  
S. I. Semenenko
Keyword(s):  
Oxidative Stress ◽  
Traumatic Brain Injury ◽  
Lipid Peroxidation ◽  
Antioxidant Enzymes ◽  
Brain Injury ◽  
Oxidative Degradation ◽  
Male Rats ◽  
Control Group ◽  
Nacl Solution ◽  
Amantadine Sulfate

Annotation. An important measure of intensive care in patients with traumatic brain injury (TBI) is the use of pharmacotherapeutic agents with antioxidant properties. The aim of this study was to evaluate the effect of ademol compared with amantadine sulfate and 0.9% NaCl solution on the course of oxidative stress in the brain of TBI rats. The experiments were performed on 28 white male rats weighing 160-190 g. The experimental TBI model of severe severity was caused by the action of a carbon dioxide flow under pressure created using a gas balloon pneumatic gun. The therapeutic effect of ademol on model TBI was evaluated with a 2 mg/kg dose. The pseudoperated animals and control group received a 0.9% solution of NaCl and amantadine sulfate at a dose of 2 ml/kg and 5 mg/kg i/v. Data were processed using StatPlus 2009. We used the parametric criterion of t-Student, non-parametric criterion of W. White, paired criterion Ť. Wilcoxon, Fisher's angular transformation at p <0,05. In the course of the experiment, it was found that treatment of rats with TBI ademol leads to a decrease in the activity of lipid peroxidation and oxidative degradation of proteins (p<0.05) and promotes the normalization of the activity of antioxidant enzymes in cells of traumatically damaged brain (p<0.05). The use of ademol compared to amantadine sulfate and 0.9% NaCl solution was accompanied by a more significant decrease in the activity of lipid peroxidation and oxidative degradation of proteins and an improvement in the level of antioxidant enzymes in damaged brain of animals with TBI (p<0.05).

Sign in / Sign up

Export Citation Format

Share Document