We have here presented an extended theoretical and experimental study of hydroxyl radical (HR) trapping assay by ascorbic acid (AA). 2,4-Dimethoxyaniline (DMA) in the presence of hydrogen peroxide ...and horseradish peroxidase (HRP) produces an imine form of 2,4-DMA (DMA*), a violet colored product with an UV–Vis absorption maximum at 540 nm. The formation of the violet colored product was inhibited by the addition of AA. Fukui functions and dual descriptor enumerating the local and global electron densities of the atoms on the DMA, AA, and HR systems were calculated. The preferential electron density pattern on DMA, AA, and HR was assessed by left and right Fukui functionals at constant external potential. Highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap for DMA and AA were found to be 8.834 and 10.908 eV, respectively, and singly occupied molecular orbital–highest occupied molecular orbital (SOMO–HOMO) gap for HR was 16.872 eV. The global softness for DMA, HR, and AA was 12.99, 6.10, and 11.70, respectively. The electronic transitions (n to π* and
π
to
π
*) of the proposed colored product were simulated by time dependent-density functional theory (TD-DFT) calculation with its correlation with the practical UV–Vis data. Natural bond order analysis (NBO) and electrostatic potential (ESP) providing theoretical information on the relative electron density over the atomic position of AA and DMA were presented. This article can provide a unique way of understanding the position of HR radical attack on AA and DMA.
Graphical abstract
A new spectrophotometric method for the analysis of creatinine concentration in human serum samples is developed. The method explores the oxidation of p-methylamino phenol sulfate (Metol) in the ...presence of copper sulfate and creatinine which yields an intense violet colored species with maximum absorbance at 530nm. The calibration graph of creatinine by fixed time assay ranged from 4.4 to 620μM. Recovery of creatinine in human serum samples varied from 101% to 106%. Limit of detection and limit of quantification were 0.145μM and 0.487μM respectively. Sandell’s sensitivity was 0.112μgcm−2 and molar absorptivity was 0.101×104Lmol−1cm−1. Within day precision was 2.5–4.8% and day-to-day precision range was 3.2–7.8%. The robustness and ruggedness of the method expressed in RSD values ranged from 0.78% to 2.12% and 1.32% to 3.46% respectively, suggesting that the developed method was rugged. This method provides good sensitivity and is comparable to standard Jaffe’s method with comparatively less interference from foreign substances.
Chlorpromazine hydrochloride (CPH) (3-(2-chloro-phenothiazine-10-yl)-propyl dimethylamine hydrochloride) has been the subject of a large number of studies employing a broad spectrum of oxidants, and ...chosen to examine the course of electron transfer reactions. We report on a method to determine the antioxidant activity of some food and medicinal plants using the oxidation of CPH by chromium(VI) to form a stable CPH radical in the 1:1 orthophosphoric acid–ethyl alcohol (OPA-EtOH) medium. The pink color of the control solution was measured at λmax of 530 nm. Nine standard antioxidants have been studied by this method, along with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. The EC50, TEC50, antioxidant efficacy and the stoichiometric values for antioxidants have been evaluated. The radical scavenging activity expressed as EC50 ranged from 9.2 μg/mL in Camellia sinensis to 448.18 μg/mL in Cuminum cyminum. The application of a simple and versatile antioxidant capacity assay for dietary polyphenols and medicinal plant extracts, which are commonly used in Ayurveda opens its relevance in the field of antioxidant analysis.
This paper presents a novel spectrophotometric method to measure peroxidase activity using paraphenylenediamine dihydrochloride (PPDD) and Mequinol (MQ). The PPDD traps the free radical, and gets ...oxidized to electrophilic 1,4-diimine; this couples with MQ to an give intense violet-colored chromogenic species with the maximum absorbance at 560 nm. This assay was adopted for the quantification of hydrogen peroxide between 10 × 10−6 to 80 × 10−6 M. From the kinetic data, a two-substrate ping-pong mechanism of peroxidase was established. Catalytic efficiency and catalytic power of commercial peroxidase were 0.204 × 106 M−1 min−1 and 2.86 × 10−4 min−1, respectively. The catalytic constant (kcat) of the proposed method was 0.2080 × 103 min−1. As a simple, rapid, precise and sensitive technique, PPDD-MQ stands as a potential replacement for the traditional guaiacol method. Applications to the plant extracts increase its relevance in the field of biochemical analysis.
A simple and sensitive spectrophotometric method for the determination of chromium has been developed. The method is based on the diazotization of Dapsone in hydroxylamine hydrochloride medium and ...coupling with N-(1-Napthyl) Ethylene Diamine Dihydrochloride by electrophilic substitution to produce an intense pink azo-dye, which has absorption maximum at 540 nm. The Beer’s law is obeyed from 0.02-1.0 μg mL
−1
and the molar absorptivity is 3.4854 L mol
−1
cm
−1
. The Limits of quantification and Limit of detection of the proposed method are 0.0012 μg mL
−1
and 0.0039 μg mL
−1
respectively. The method has been successfully applied for the determination of chromium in water samples and the results were statistically evaluated with that of the reference method.
A highly sensitive spectrophotometric method for the analysis of catecholamine drugs; L-dopa and methyldopa, is described. The analysis is based on the reaction of drug molecules with vanadium (V) ...which is reduced to vanadium (IV) and form complex with eriochrome cyanine R to give products having maximum absorbance (lmax) at 565 nm. Beer's law is obeyed in the range 0.028-0.84 and 0.099-0.996 mg mL-1 for L-dopa and methyldopa, respectively. The statistical analysis as well as comparison with reported methods demonstrated high precision and accuracy of the proposed method. The method was successfully applied in the analysis of pharmaceutical preparations.
Display omitted
•Catalase defends against oxidative stress associated with pathologic conditions.•Measurement of its activity is fundamentally a new approach for antioxidant therapy.•Efficacy of the ...proposed method has been proved by evaluating analytical parameters.•The method is rapid, facile, sensitive and reproducible.
A novel method has been proposed to develop a simple, rapid, sensitive and affordable chromogenic attempt for the quantification of catalase (CAT) activity in blood samples. The method is based on the oxidation of pyrocatechol (PC) to give quinone form which by oxidative coupling with aminyl radical of 4-aminoantipyrine (4-AAP) resulting from H2O2/CAT to produce a pink colored quinone-imine product with λmax = 530 nm in a 100 mmol/L of tris buffer of pH 9.8 at room temperature (30 °C). The linearity of CAT assay was between 0.316 and 10 U/mL. The accuracy ranges for CAT having concentrations of 1.25, 5 and 7.5 μmol/L were 89–105.52, 90–107%, and 91–104.58% respectively. Within-run and between-run precision studies showed CV’s of 1.98–3.02% (n = 7) and 2.97–4.40% (n = 7), respectively. The detection and quantification limits of CAT were 0.12 and 0.225 μmol/L, respectively. The Michaelis-Menten constant and maximum velocity of the reaction was Km = 1.052 mM and Vmax = 0.168 μmol/min, respectively. The present method provides a convenient means for investigating the usefulness of CAT measurements in biological sample assessing the potential for free radical-induced pathology.
A simple and accurate method for the determination of chloroquine diphosphate (CQ), pyrimethamine (PYM) and trimethoprim
(TMP) in pure, pharmaceutical and urine samples is described. The method ...involved an ion pair extraction procedure with chloroform
using an acid base indicator, bromocresol purple (BCP), as a counter ion. The ion pair extracted in organic phase was yellow,
and the absorbance was measured at λmax = 420 nm. Beer’s law was obeyed over the concentration range of 1.25-8.75, 0.62-7.5,
and 1.25-10.71 μg/mL, respectively. The Sandell’s sensitivity was 0.01258, 0.01102 and 0.01464 μg/cm2. The Ringbom optimum concentration range, which was 2.5-7.5, 1.25-7.5 and 2.5-10.7 μg/mL for CQ, PYM, and TMP, respectively, exhibited reliability of the method. Stoichiometry and thermodynamic of the complexes were evaluated by Job’s method and Benesi-Hildebrand plot. The statistical results of intra- and inter-day estimation of drugs and comparison with the reported methods demonstrated high precision and accuracy of the method. The procedure was rapid, simple and suitable for quality control purpose.
Electrophysiological systems are prone to release free radicals for functioning of biological system with proper balancing of antioxidant-prooxidant ratio for establishing a healthy living system. ...The biostress condition releases different reactive oxygen species, such as hydroxyl, alkoxyl, superoxide, hydrogen peroxide, hydroperoxyl, ozone, singlet oxygen, hypochlorus acid, thiyl radical, etc. This review tries to discuss the general aspects of the antioxidant assay methodologies that are currently used for the detection of antioxidant property. The entire review has been divided into three different sections. The first deals with the release of free radical by mitochondrial dysfuctioning and its curbing action by local antioxidants. The second and third sections discuss the general procedure adopted and reaction mechanism involved in the assay procedure along with the limitations and advantages.
PDF
