scholarly journals Different values obtained by the FRAP method for the determination of slowly and rapidly reacting phenols

2022 ◽  
Keyword(s):  
Caffeic Acid ◽  
Sinapinic Acid ◽  
Storage Conditions ◽  
Syringic Acid ◽  
Iron Ions ◽  
Reaction Solution ◽  
Total Antioxidant ◽  
The Common ◽  
Over Time

Abstract A number of methods have been applied to measure total antioxidant capacity (TAC), including FRAP, which is based on reducing the amount of iron ions in a complex compound. Researchers often use measurement of absorbance 10 min after mixing a sample with the FRAP reaction solution to calculate TAC. The FRAP solution has been shown to alter absorbance over time by ca 0.0010–0.0020 per hour, under storage conditions. This article intends to show that some substances do not fully or sufficiently react within the common analysis period. It is evident from the results that some substances react more quickly and others very slowly. Absorbance in relation to various phenols was measured. Compared to the levels of absorbance at 10 min, mean absorbance at 48 h was higher by 5,395% for vanillin, 426% for caffeic acid, 170% for sinapinic acid, 67% for gallic acid, 19% for syringic acid, and only by 4% for Trolox. Results for vanillin and caffeic acid indicate potential auto-catalysis.

scholarly journals High-Performance Thin-Layer Chromatography Densitometric Method for the Simultaneous Determination of Three Phenolic Acids in Syzygium aromaticum (L.) Merr. & Perry

2008 ◽  
Vol 91 (5) ◽  
pp. 1169-1173 ◽  
Author(s):  
Subha Rastogi ◽  
Madan M Pandey ◽  
Ajay K S Rawat
Keyword(s):  
Thin Layer ◽  
Gallic Acid ◽  
Simultaneous Determination ◽  
Caffeic Acid ◽  
Correlation Coefficient ◽  
Phenolic Acids ◽  
High Performance ◽  
Syringic Acid ◽  
Syzygium Aromaticum

Abstract A simple, precise, and rapid high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous determination of 3 phenolic acids, i.e., gallic acid, caffeic acid, and syringic acid, in the dried buds of Syzygium aromaticum, commonly known as clove. HPTLC was performed on silica gel 60F254 plates with tolueneethyl acetateformic acid (8 2 1) mobile phase and densitometric scanning at 280 nm. The method was validated for selectivity, linearity, precision, and repeatability. Instrumental precision coefficient of variation (CV) was 0.88, 0.93, and 0.98% and repeatability of the method (CV) was 0.76, 0.64, and 0.69% for gallic acid, caffeic acid, and syringic acid, respectively. The linear concentration ranges were 4003200 ng/spot with a correlation coefficient of 0.993 for gallic acid, 4403520 ng/spot with a correlation coefficient of 0.994 for caffeic acid, and 4004000 ng/spot with a correlation coefficient of 0.993 for syringic acid. The average recoveries of gallic acid, caffeic acid, and syringic acid were 96.3, 95.7, and 92.4%, respectively. Gallic acid, caffeic acid, and syringic acid were present at levels of 1.58, 0.06, and 0.05% (w/w), respectively, in S. aromaticum. This method is simple, accurate, precise, and economical and can be used for routine quality control.

Articulatory Generalization in Two Word-Medial, Ambisyllabic Contexts

1988 ◽  
Vol 19 (3) ◽  
pp. 251-258 ◽  
Author(s):  
Virginia I. Wolfe ◽  
Suzanne D. Blocker ◽  
Norma J. Prater
Keyword(s):  
Common View ◽  
Perceptual Salience ◽  
The Common ◽  
Unitary Concept ◽  
Over Time

Articulatory generalization of velar cognates /k/, /g/ in two phonologically disordered children was studied over time as a function of sequential word-morpheme position training. Although patterns of contextual acquisition differed, correct responses to the word-medial, inflected context (e.g., "picking," "hugging") occurred earlier and exceeded those to the word-medial, noninflected context (e.g., "bacon," "wagon"). This finding indicates that the common view of the word-medial position as a unitary concept is an oversimplification. Possible explanations for superior generalization to the word-medial, inflected position are discussed in terms of coarticulation, perceptual salience, and the representational integrity of the word.

Analysis of Squalene and Its Transformation By-Products in Latent Fingermarks by Ultrahigh-Pressure Liquid Chromatography-High Resolution Accurate Mass Orbitrap™ Mass Spectrometry

2019 ◽  
Author(s):  
Buddhika Dorakumbura ◽  
Francesco Busetti ◽  
Simon Lewis
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
High Resolution ◽  
Storage Conditions ◽  
Ultrahigh Pressure ◽  
Accurate Mass ◽  
Rational Approach ◽  
By Products ◽  
Over Time ◽  
High Resolution Accurate Mass

<p>Transformation of squalene and its by-products in fingermarks over time under different storage conditions (light, dark and underwater) was examined through ultrahigh-pressure liquid chromatography high resolution accurate mass Orbitrap™ mass spectrometry. Complications of assessing fingermark compositional variation over time using multiple samples with varying initial compositions were elucidated and a more rational approach was successfully demonstrated. Squalene was detected in all fresh natural fingermarks and the amount ranged between 0.20 to 11.32 μg/5 fingertips. A notable difference in the transformation of squalene was observed with different storage conditions, where a dark aquatic environment accelerated degradation of squalene compared to dark but dry conditions. Squalene monohydroperoxide was extremely short-lived in natural deposits while the amount of squalene epoxide was still increasing relative to the initial amount, after ageing under dark and aquatic conditions for up to 7 days. Some oxidation by-products of cholesterol were also tentatively identified, which exhibited a growth over time against their initial concentration under any of the storage condition tested. These by-products, therefore, show potential as biomarkers for targeted visualisation of aged deposits.</p>

Use of Phosphatidylcholine in the Treatment of Localized Fat Deposits. Results and expectations

2017 ◽  
Vol 68 (7) ◽  
pp. 1438-1441 ◽  
Author(s):  
Sorin Berbece ◽  
Dan Iliescu ◽  
Valeriu Ardeleanu ◽  
Alexandru Nicolau ◽  
Radu Cristian Jecan
Keyword(s):  
World Health Organisation ◽  
Normal Weight ◽  
World Health ◽  
Basic Substance ◽  
Physical Exercises ◽  
Fat Deposits ◽  
The World ◽  
The Common ◽  
Global Health Problem ◽  
Over Time

Obesity represents a global health problem. According to the latest studies released by the World Health Organisation (WHO), 1.7 billion currently in excess of normal weight individuals, of which approx. 75% are overweight (body mass index - BMI 25 to 30). The common form of excess adipose tissue manifestation in overweight individuals is localized fat deposits with high (abdominal) or low (buttocks and thighs) disposition. Although the overweight can be corrected relatively easy by changing behavioral habits or food, a constant physical exercises program or following a diet food are not accessible to all through the efforts of will, financial and time involved. Several methods have been studied and tested over time to eliminate more or less invasive fat deposits with varying efficacy and adverse effects. Chemical lipolysis using phosphatidylcholine as the basic substance was initially used in hypercholesterolemia and its complications and was rapidly adopted in mesotherapy techniques for the treatment of fat deposits. This study reveals the results obtained using Dermastabilon on a sample of 16 patients, the time allocated to treatment and discomfort being minimal, and rapid and notable results. There were no side effects.

Alcohol Determination by HPLC with Postcolumn Derivatization Based on the Thiosulfate-catalyzed Reaction of Alcohols and Cerium(IV) and Fluorescence Detection of Cerium(III)

2020 ◽  
Vol 16 ◽  
Author(s):  
Ikko Mikami ◽  
Eri Shibayama ◽  
Kengo Takagi
Keyword(s):  
Detection Limit ◽  
Fluorescence Detection ◽  
Reaction Rate ◽  
Detection Method ◽  
Fluorescence Detector ◽  
Reaction Solution ◽  
Optimum Detection ◽  
Postcolumn Derivatization ◽  
Sensitive Method

Background: Determination of a reducing substance based on the reaction between Ce(IV) and a reducing substance and fluorescence detection of Ce(III) generated has been reported as a selective and sensitive method. However, this method could not be applied to the determination of alcohol due to the low reaction rate of alcohol and Ce(IV). Objective: We found that thiosulfate catalytically enhanced reaction of alcohols (such as, methanol, ethanol, and propanol) and Ce(IV). Utilizing this effect, we developed a new method for the determination of alcohols. Results: In the presence of thiosulfate, an increase in fluorescence intensity was detected by injecting alcohol at concentrations of several millimolar, whereas it was not observed even at the concentration of 10% v/v (2 M for ethanol) in the absence of thiosulfate. The optimum detection conditions were determined to be 4.0 mM Ce(IV) sulfate and 0.50 mM thiosulfate, and the detection limit (S/N = 3) of ethanol under these conditions was 1 mM. In the calibration curves, changes in the slope were observed when the alcohol concentrations were approximately 10–25 mM. Using a thiosulfate solution containing ethanol as the reaction solution, a calibration curve without any change in slope was obtained, although the concentration of ethanol at the detection limit increased. The alcohols in the liquor and fuel were successfully analyzed using the proposed detection method as a postcolumn reaction. Conclusion: This new alcohol detection method using a versatile fluorescence detector can be applied to the postcolumn reaction of HPLC omitting need of time-consuming pretreatment processes.

Determination of the Average Energy of Iron Ions in the Axial Direction of a Micropinch Discharge Using an Ion Collector

2019 ◽  
Vol 82 (10) ◽  
pp. 1387-1391
Author(s):  
S. A. Sarantsev ◽  
I. F. Raevskii ◽  
V. A. Kostyushin ◽  
A. S. Savelov
Keyword(s):  
Average Energy ◽  
Axial Direction ◽  
Iron Ions

scholarly journals Determination of antioxidant activity and phenolic compounds for basic standardization of Turkish propolis

2021 ◽  
Vol 64 (1) ◽  
Author(s):  
Aslı Özkök ◽  
Merve Keskin ◽  
Aslı Elif Tanuğur Samancı ◽  
Elif Yorulmaz Önder ◽  
Çiğdem Takma
Keyword(s):  
Antioxidant Capacity ◽  
Caffeic Acid ◽  
Caffeic Acid Phenethyl Ester ◽  
Total Phenolic ◽  
Scaling Analysis ◽  
Flavonoid Content ◽  
Multidimensional Scaling Analysis ◽  
Flavonoid Quercetin ◽  
Phenolic And Flavonoid

AbstractThis study aimed to determine the standard amount of antioxidant content and compounds of the propolis for the standardization of propolis. For this purpose, the total flavonoids, total phenolic, CUPRAC antioxidant capacity content and the diversity of phenolic and flavonoid components of these propolis samples were found by HPLC determined at the 23 propolis samples which were collected different regions of Turkey. Beside that, the similarities and differences of these 23 provinces to each other according to their antioxidant capacities were investigated by multidimensional scaling analysis. The total flavonoid content in the propolis samples were determined between 21.28 and 152.56 mg CE/g. The total phenolic content in the propolis samples was found between 34.53 mg and 259.4 mg GAE/g. CUPRAC antioxidant capacity of the propolis samples and antioxidant range was found from 95.35 to 710.43 mg TE/g. Also, 4 flavonoid [Quercetin (min.1.12–max.4.14 mg/g), Galangin (min.0.72–max.40.79 mg/g), Apigenin (min.1.07–max.17.35 mg/g), Pinocembrin (min.1.32–max.39.92 mg/g] and 6 phenolic acid [Caffeic acid (min.1.20–max.7.6 mg/g), p-Coumaric acid (min.1.26–max.4.47 mg/g), trans-Ferulic acid (min.1.28–max.4.92 mg/g), Protocatechuic acid (1.78 mg/g), trans-Cinnamic acid (min.1.05–max.3.83 mg/g), Caffeic Acid Phenethyl Ester (CAPE) (min.1.41–max.30.15 mg/g)] components were detected as mg/g, in different ratios in propolis samples collected from different regions. The feature of this study, so far, is to have the maximum number of samples representing the Turkish propolis, and so is thought to help to national and international propolis standard workings.

scholarly journals Acute symptoms of mild to moderate COVID-19 are highly heterogeneous across individuals and over time

2021 ◽  
Author(s):  
Thomas L Rodebaugh ◽  
Madelyn R Frumkin ◽  
Angela M Reiersen ◽  
Eric J Lenze ◽  
Michael S Avidan ◽  
...  
Keyword(s):  
Temporal Dynamics ◽  
Survey Methods ◽  
Clinical Care ◽  
Clinical Deterioration ◽  
Symptom Profiles ◽  
Fluctuating Course ◽  
The Common ◽  
Symptom Changes ◽  
Over Time

Abstract Background The symptoms of COVID-19 appear to be heterogenous, and the typical course of these symptoms is unknown. Our objectives were to characterize the common trajectories of COVID-19 symptoms and assess how symptom course predicts other symptom changes as well as clinical deterioration. Methods 162 participants with acute COVID-19 responded to surveys up to 31 times for up to 17 days. Several statistical methods were used to characterize the temporal dynamics of these symptoms. Because nine participants showed clinical deterioration, we explored whether these participants showed any differences in symptom profiles. Results Trajectories varied greatly between individuals, with many having persistently severe symptoms or developing new symptoms several days after being diagnosed. A typical trajectory was for a symptom to improve at a decremental rate, with most symptoms still persisting to some degree at the end of the reporting period. The pattern of symptoms over time suggested a fluctuating course for many patients. Participants who showed clinical deterioration were more likely to present with higher reports of severity of cough and diarrhea. Conclusion The course of symptoms during the initial weeks of COVID-19 is highly heterogeneous and is neither predictable nor easily characterized using typical survey methods. This has implications for clinical care and early-treatment clinical trials. Additional research is needed to determine whether the decelerating improvement pattern seen in our data is related to the phenomenon of patients reporting long-term symptoms, and whether higher symptoms of diarrhea in early illness presages deterioration.

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