Application of Pyroelectric Sensors Based on PVDF Films for EPR Spectra Detection by Heat Release

Pyroelectrics are a wide class of materials that change their polarization when the system temperature varies. This effect is utilized for a number of different commercial and industrial applications ranging from simple thermal sensors and laser interferometers to water vapor harvesting. Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for studying the structure and dynamics of materials with unpaired electrons. Since heating accompanies a resonant change of the orientation of electron spins in an external magnetic field, pyroelectrics can be utilized as versatile detectors for so-called indirect detection of the EPR signal. In this work, we investigated three different types of PVDF (polyvinylidene difluoride) standard pyroelectric films with indium tin oxide, Cu/Ni, and Au coatings to determine their sensitivity for detecting EPR signals. All the films were shown to be able to detect the EPR spectra of about 1 μg of a standard stable free radical by heat release. A comparative study based on the calculation of the noise-equivalent power and specific detectivity from experimental spectra showed that the Au coated PVDF film is the most promising active element for measuring the EPR signal. Using the best achieved sensitivity, estimation is given whether this is sufficient for using a PVDF-based pyrodetector for indirectly detecting EPR spectra by recombination heat release or not.

Correlation Analysis of Antioxidant Activities with Tannin, Total Flavonoid, and Total Phenolic Contents of Nutmeg (Myristica fragrans Houtt) Fruit Precipitated by Egg white

The nutmeg (Myristica fragrans) flesh extract has a strong antioxidant activity. Therefore, M. fragrans flesh can be developed for functional drinks which are sources rich in antioxidants good for the prevention and treatment of diseases such as cancer and cardiovascular diseases. However, the tannins' content can cause a bitter and sour taste. Therefore, the tannins content should be reduced by the addition of egg white. The purpose of this study is to find out the comparison of antioxidant activity between a combination of M. fragrans flesh extract with various concentrations of egg white and to correlate its antioxidant activities with tannin, total flavonoid, and total phenolic contents. The antioxidant activities were conducted on M. fragrans flesh extract by using DPPH and ABTS radicals. Tannin, total flavonoid, and total phenolic contents from M. fragrans flesh extract were also tested. The M. fragrans flesh extracts without addition egg white have a strong antioxidant in scavenging the stable free radical ABTS (89.980±0.480 µg/mL) and intermediate antioxidant in scavenging the stable free radical DPPH (105.669±0.102 µg/mL). It is followed accordingly by tannin, total flavonoid, and total phenolic contents, namely 14.034±0.100 %w/w TAE, 26.929±0.129 %w/w QE, and 53.164±0.129 %w/w GAE, respectively. Correlation of tannin, total flavonoid, and total phenolic contents, which inhibited DPPH and ABTS radicals had R2 values of about 89.23-97.63%. It showed that antioxidant activity is strongly influenced by the tannin, total flavonoid, and total phenolic contents. Therefore, precipitation from the tannin-protein bond caused antioxidant activities were decreased.

ANTIOXIDANT PROPERTIES AND EFFECTS OF APORPHINE ALKALOIDS AND THEIR PHENANTHRENE SECO-ISOMERS ON ACETYLCHOLINESTERASE ACTIVITY

For the first time, model’s phenanthrene seco-alkaloids (seco-glaucine and seco-boldine) obtained in the medium of subcritical water SBW) from plant aporphine alkaloids were studied as antioxidants and inhibitors of acetylcholinesterase (AChE). Antioxidant activity (in vitro) of model’s aporphine and phenanthrene alkaloids: boldine, seco-boldine, glaucine and seco-glaucine, (BD, s-BD, GL and s-GL) was studied in the reaction with a stable free radical DPPH (1,1- diphenyl-2-picrylhydrazyl). In vivo, antioxidant activity was determined in a bioluminescent test system using genetically modified E. coli strains. In experiments in vitro (DPPH-test) and in vivo (biotest) phenanthrene alkaloids s-GL and s-BD demonstrate the higher antioxidant activity than their aporphine precursors GL and BD. For the study (in vitro) of the anticholinesterase activity of alkaloids and their phenanthrene seco-isomers used the “Ellman’s method” with minor modifications. The data on the inhibitory activity of the AChE enzyme with aporphine and phenanthrene alkaloids, expressed as IC50 values obtained from dose-response curves, demonstrate that the inhibitory activity for seco-boldine (IC50 = 0.21 mM) and seco-glaucine (IC50 = 0.04 mM ) is higher than for the initial aporphine alkaloids boldine (IC50 = 0.29 mM) and glaucine (IC50 = 0.44 mM), respectively. Thus, it has been shown that phenanthrene alkaloids obtained in SBW exhibit higher antioxidant activity and better inhibiting AChE-activity than their aporphine precursors.

Antiradical activity of novel 4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazole-3-thiol derivatives

The process of studying free radicals began in the middle of the last century (the free radical theory of aging in 1956). Multiple studies have revealed the effect of free radicals on the cells of the body and the development of various diseases, such as diabetes, autoimmune diseases, diseases of the nervous system, and others. As a result, the term antioxidant has emerged, compounds that reduce and prevent the effects of free radicals. Most of the newly synthesized substances are studied for their antiradical properties. 1,2,4-Triazole derivatives are no exception, which has already proven themselves as biologically active compounds. The aim of this work was the investigation antiradical activity among 4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazole-3-thiol derivatives. Materials and methods. Previously synthesized 4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazole-3-thiol derivatives were used as test compounds. The research of antiradical activity was based on the interaction between 4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazole-3-thiol derivatives and 2,2-diphenyl-1-picrylhydrazyl (DPPH) in vitro. DPPH is a stable free radical. The color of its alcoholic solutions were intense purple (λmax = 517 nm). When DPPH interacted with compounds that were capable of scavenging free radicals, it produced products. These products are yellow in color and do not absorb light of the aforementioned wavelength. The study was carried out according to the method. Results. The antiradical activity of 10 new 4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazole-3-thiol derivatives was studied. Most of the test compounds show antiradical activity against DPPH. Compound 1 was the most active at a concentration of 1 × 10-3 M and the antiradical effect was close to ascorbic acid. Conclusions. The most active compound is 4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazole-3-thiol, which in a concentration of 1 × 10-3 M has an antiradical effect in 88.89 %. When reducing the concentration to 1 × 10-4 M, also reduces the antiradical activity to 53.78 %. Some conclusions are drawn regarding the “structure – effect” dependence between 4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazole-3-thiol derivatives: – the introduction of 4-fluorobenzylidene radical (compound 2) into the 4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazole-3-thiol molecule results in a slight decrease in activity; – the introduction of 2-hydroxybenzylidene radical (compound 3) into initial molecule results a high antiradical effect, which hardly changes with decreasing concentration; – transformation to 2-((5-(thiophen-2-ylmethyl)-4-((R)amino)-4H-1,2,4-triazol-3-yl)thio)acetic acid has almost no effect on antiradical activity, except for compound 9 (the antiradical effect is reduse).

The Chemistry of DPPH· Free Radical and Congeners

Since the discovery in 1922 of 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl stable free radical (DPPH·), the chemistry of such open-shell compounds has developed continuously, allowing for both theoretical and practical advances in the free radical chemistry area. This review presents the important, general and modern aspects of the chemistry of hydrazyl free radicals and the science behind it.

HPTLC study to determine the antioxidant activity of dried leaves of Portulaca oleracea L.

This present study involves the assessment of the anti-oxidant activity study of the sample which was obtained from the methanolic extracts of dried leaves of Portulaca Oleracea L.(common name Purslane). Purslane is a rich source of Vitamin A, Vitamin-C and some other B-complex vitamins like riboflavin, niacin, pyridoxine and carotenoids which are known powerful natural anti-oxidants. Anti-oxidants are compounds that inhibit oxidation. This methanolic extract of leaves was evaluated for the determination of its anti-oxidant efficiency by using 1,1–diphenyl-2-picryl-hydrazyl (DPPH) by using Silica TLC plates on Camag High-Performance Thin Layer Chromatography (HPTLC) system using visionCATS software. Densitograms and chromatographs obtained show the presence of anti-oxidant activity. It is a rapid, inexpensive and straightforward method to measure anti-oxidant properties of substances after separation by HPTLC. It involves the use of the free radical, 2, 2-Diphenyl-1- picrylhydrazyl (DPPH) which is widely used to test the ability of compounds to act as free radical scavengers or hydrogen donors and to evaluate anti-oxidant activity. When Anti-oxidants substances react with DPPH, which is a stable free radical becomes paired off in the presence of a hydrogen donor (e.g., a free radical scavenging anti-oxidant) and is reduced to the DPPHH. As a consequence, the absorbance's decreased from the DPPH.

Ceria nanorods as highly stable free radical scavengers for highly durable proton exchange membranes

Morphology regulation induced high stability of ceria in proton exchange membrane.

Extraction, Chemical Composition, Antioxidant Property and In vitro Anticancer Activity of Silymarin from Silybum Marianum On Kb and A549 Cell Lines

Introduction: This study aimed to evaluate the antioxidant property of silymarin (SM) extracted from the seed of Silybum marianum and its anticancer activity on KB and A549 cell lines following 24, 48, and 72 h of treatment. Methods: Ten grams of powdered S. marianum seeds were defatted using n-hexane for 6 hours and then extracted by methanol. The silymarin extracted of extraction components The extracted components of silymarin were measured by spectrophotometric assay and HPLC analysis. 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, phenol content, total flavonoid content, and total antioxidant capacity were measured to detect the antioxidant properties of SM. The anticancer activity of the SM on cell lines evaluated by MTT. Results: In HPLC analysis, more than 50% of the peaks were related to silibin A and B. SM was reducedDPPH (the stable free radical) with a 50% inhibitory concentration (IC50) of 6.56 μg/ ml in comparison with butylated hydroxyl toluene (BHT), which indicated an IC50 of ~3.9 μg/ ml.The cytotoxicity effect of SM on the cell lines was studied by MTT assay. The cytotoxicity effect of the extracted silymarin on KB and A549 cell lines was observed up to 80 and 70% at 156 and 78 µg/ml, respectively. The IC50 value of the extracted SM on KB and A549 cell lines after 24 hours of treatment was seen at 555 and 511 µg/ml, respectively. Conclusion: Due to the good antioxidant and anticancer properties of the isolated silymarin, its use as an anticancer drug is suggested.