Ascorbic Acid Inhibition Research Articles

“ESTIMATION OF RADICAL SCAVENGING POTENTIAL OF SELECTED MEDICINAL PLANTS OF LAHORE, PAKISTAN”


 
 
 In the current research, in vitro antiradical potential of some medicinal trees of Lahore, Pakistan was investigated. Various fruits and pods of 25 medicinal plants (Prosopis juliflora, Carissa carandas, Ceiba speciosa, Heterophragma adenophyllum Cestrum diurnum Jacaranda mimosifolia, Diospyros malabarica, Terminalia bellerica, Ficus lyrata, Diospyros peregrine, Cinnamomum verum, Erysimum cheiri, Buchanania lanzan, Withania somnifera, Fagonia arabica, Berberis lycium, Strychnos potatorum, Matthiola incana, Ziziphora tenuior, Centaurea behen, Rosa indica, Punica granatum, Lodoicea maldivica, Cassia absus, Celastrus paniculatus) were extracted by ethanol. Different concentrations of fruit extracts (1, 0.5, 0.25, 0.125 mg/mL) were prepared to evaluate in vitro antioxidant activity. The DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging method was performed and compared with standards like Vitamin E, BHT (Butylated hydroxytoluene) and ascorbic acid. Many plant extracts exhibited 80% of DPPH radical scavenging activity. F. Arabica, S. potatorum, M. incana, P. granatum, C. behen, W. somnifera, T. bellerica, and H. adenophyllum showed significant anti-radical potential (98.4±0.52, 96.40±0.52, 96.42±0.51, 94.58±0.52, 94.47±0.50, 94.65±0.56, 94.55±0.50, 91.42±0.51% inhibition, respectively) at 1 mg/mL equivalent to standards i.e. Vitamin E, BHT and ascorbic acid inhibition (88.25±0.2, 78.1±0.3 and 40.51±0.17%), respectively. Moreover, the dose dependent activity was observed as decline in the percentage inhibition at lower extracts concentration. The 50% inhibitory concentration (IC50) was also determined for the extracts that varied from 0.014± 0.001 (W. somnifera and J. mimosifolia) to 2.69±0.001 (B.lanzan) mg/mL depending on the sample extracts. The natural antioxidants in plants may be used in foods and natural products as a substitute to synthetic antioxidants, which have side effects.
 
 

Polyvinylpyrrolidone-stabilized Pt nanoclusters as robust oxidase mimics for selective detection of ascorbic acid

In this work, the Pt nanoclusters with an average size of 1.7 ± 0.3 nm were prepared by a facile and green method using polyvinylpyrrolidone (PVP) as both stabilizer and reductant. The oxidase-like activity of PVP-stabilized Pt nanoclusters (PVP-Pt NCs) was investigated by the catalytic oxidation of o-phenylenediamine (OPD). The mechanism studies indicated that PVP-Pt NCs performed as oxidase enzyme mimics by catalyzing the dissolved oxygen to generate the reactive oxygen species (singlet oxygen and superoxide anion) intermediates. Ascorbic acid (AA) could also be oxidized to dehydroascorbic acid (DHA) which could react with OPD to generate a fluorescent compound. On the basis of the robust oxidase-like activity of PVP-Pt NCs, both colorimetric assay and fluorescence method for AA determination were established. Compared with colorimetric assay, the fluorescence method showed higher sensitivity and selectivity for AA detection. The proposed fluorescence method with the LOD of 1.17 μM could overcome the interference of most reducing substances and showed promising applications in biosensor. The as-prepared PVP-Pt NCs possessed intrinsic oxidase-like property by catalyzing dissolved oxygen to ROS (superoxide anions (·O 2 - ) and singlet oxygen ( 1 O 2 )) which could oxide the OPD to OPD ox . The inhibition of AA to the catalytic oxidation of OPD was employed to establish the colorimetric assay for AA determination. AA could also be oxidized to DHA by·O 2 - and 1 O 2 intermediates, and the DHA could react with OPD to form QD with a fluorescence emission peak at 434 nm. The fluorescence method for AA detection was carried out when the solution changed to yellow color which was the signal of the reaction terminal. Comparing with colorimetric assay, the fluorescence method exhibited enhanced sensitivity and selectivity.

Effect of Microwave Power and Time on Total Phenolic Contents and Antioxidant Characteristics of Microwave Assisted Extracts of Watermelon Rind Powder

Watermelon is gaining importance as a functional food due to its therapeutic effect. The therapeutic effect of watermelon has been reported and has been attributed to antioxidant constitutes.The major component in watermelon rind is citrulline that has a strong antioxidant effect which protect body from free-radical damage.Objective:This study was conducted to investigate the effect of microwave powers (150 W, 300 W & 450 W) and time intervals (1,3 & 5 minutes) on total phenolic content (TPC) and total flavonoid content (TFC) and antioxidant characteristics i.e. DPPH and ferric reducing antioxidant potential (FRAP) of microwave assisted extracts of watermelon rind powder.Methods:The extracts collected after Microwave assisted extraction (MAE) of watermelon rind wereanalyzed for their antioxidant potential through different tests including total phenolic contents (TPC), total flavonoid content (TFC), DPPH assayand FRAP.Results:Microwave assisted extraction by using ethanol as a solvent at different microwave powers and various time intervals showed that total antioxidant potential was significantly higher at low microwave power such as TPC ranges obtained at 150W for 1, 3 & 5 minutes of time intervals show ranges (159.84, 160.04 & 169.71 mg GAE/100 g). While TFC ranges at 150W for time 1, 3 & 5 minutes were (21.31, 24.15 & 42.20 mg CEQ/100g) whereas DPPH ranges at 150W for time 1, 3 & 5 minutes were (53.14, 54.87 & 68.17 % ascorbic acid inhibition) and FRAP values at 150W for time 1, 3 & 5 minutes were (201.71, 221.50 & 326.43 mg FE/100g). While high microwave power 450W can result in disruption of some antioxidants at various time intervals.Conclusions:Watermelon rind is a rich source of many antioxidants andmicrowave assisted extraction technique should be implemented in the food and nutraceutical industries and microwave assisted extracts of watermelon rind should be utilize for the development of new functional food to combat many health related problems

VHTS and 3D-QSAR for the Identification of Novel Phyto-inhibitors of Farnesyltransferase: Validation of Ascorbic Acid inhibition of Farnesyltransferase in an Animal Model of Breast Cancer.

Farnesyltransferase (FTase) is a zinc enzyme that has been the subject of attention in anti-cancer research over the past. In this study, phytochemicals from Curcuma longa L., Taraxacum officinale, and Spondias mombin plants were screened for their inhibitory potentials on the human farnesyltransferase. A three-dimensional quantitative structure-activity relationship (3D-QSAR) model for the inhibition of farnesyltransferase was generated and the inhibition of farnesyltransferase by the hit, ascorbic acid was validated in an animal model of breast cancer. The lead compound, ascorbic acid makes extensive hydrogen bond interactions with key residues, lys-353, tyr-300, gly-290, leu-290 within the active site of farnesyltransferase. It downregulated the expression of FNTA mRNA in an animal model of breast cancer. The 3D-QSAR generated herein is robust, thoroughly validated, and should be employed in the pipelining of novel farnesyltransferase inhibitors. Ascorbic acid demonstrates its anticancer potentials through the inhibition of farnesyltransferase.

In Vitro and In Silico Analysis of Ascorbic Acid Towards Lanosterol 14-α-Demethylase Enzyme of Fluconazole-Resistant Candida albicans.

Antibiotic resistance is one of the major concerns and the biggest threats to the world population. The incidents of antibiotic resistance in Candida spp. were frequently recorded. In the present investigation, antifungal potential of ascorbic acid (AA) was evaluated. According to the in vitro analysis, the zone of inhibition of AA (24.75 ± 0.35mm) against C. albicans was greater as compared to other vitamins tested. AA significantly modulate the growth of C. albicans at 25mg/ml. The highest percentage (94.67%) of cell viability was observed in untreated cells, and low cell viability (29.36%) was observed in cells treated with 50mg/ml of AA (2 × MIC). Further, AO/EB (acridine orange/ethidium bromide), propidium iodide staining, and real-time qPCR confirmed the loss of membrane integrity due to membrane lesions that caused cell death. Lanosterol 14-α-demethylase (L-14α-DM) is the product of ERG11 and acted as superior drug target of C. albicans. Molecular docking analysis confirmed that active interaction of ascorbic acid with L-14α-DM. Based on the present investigation, the efficiency of AA was effectively proved through the in vitro and in silico analysis. This finding has evidenced the effectiveness of AA as a potential candidate against C. albicans.

Anti-aggregation effect of Ascorbic Acid and Quercetin on aggregated Bovine Serum Albumin Induced by Dithiothreitol: Comparison of Turbidity and Soluble Protein Fraction Methods

Studies on the anti-aggregation of dithiothreitol (DTT) induced - protein is generally determined by the fraction soluble (non-aggregated) protein. While the turbidity method is commonly used in studies of anti-aggregation, in which protein is induced by heat, in this study, both methods are compared in observing the anti-aggregation activity of ascorbic acid and quercetin toward bovine serum albumin induced by DTT. The DTT is a reducing agent for protein disulfide bonds and capable of inducing protein aggregation at physiological pH and temperature. The work was performed by the formation of Bovine Serum Albumin (BSA) aggregates induced by DTT under physiological conditions, which are pH 7.4 and 37°C. The aggregated protein profile was observed using the turbidity method at the end of incubation and measuring the difference of concentration between the fraction of soluble protein before and after incubation. The measurement was carried out using a spectrophotometer UV-Vis. The results indicate that both methods show similar inhibition profiles. The potential inhibition of ascorbic acid (AA) toward BSA protein aggregation induced by DTT increased along with incubation time. While quercetin shows the highest inhibition at 12 hours but decreased at 18 hours, this study reveals that both methods can observe the anti-aggregation activity of ascorbic acid and quercetin.

Investigation of Ascorbic Acid as Environment-Friendly Corrosion Inhibitor of Low Carbon Steel in Marine Environment

The inhibition effect of ascorbic acid against the corrosion of low carbon steel in the marine environment which is represented by NaCl 3.5% solution was studied by weight loss method. The investigations were conducted at the various concentrations of ascorbic acid and immersion time. The effect of ascorbic acid concentration and immersion time on the corrosion rate and inhibition efficiency were measured. The corrosion rate was calculated by the weight loss of the sample at initial and after immersion in the corrosive medium. The results showed that the ascorbic acid exhibit good corrosion inhibitor for low carbon steel in NaCl 3.5% solution. The rate of corrosion decreased with the increase of ascorbic acid concentration and immersion time. The efficiency inhibition of ascorbic acid on low carbon steel corrosion in NaCl 3.5% increase with the rise of concentration and immersion time, which is the maximum of 85.4% at 50 ppm and 15 days immersion time. The action of inhibition is attributed to the adsorption of the inhibitor molecules on the low carbon steel surface following Langmuir adsorption isotherm.

Geographical Variation of Antioxidant Constituent in Garhwal Region of Uttarakhand: Chinese Brake Fern (Pteris vittata)

Numerous kind of antioxidants or protecting agent are present in the living body like Glutathione is the master antioxidant produce by the liver and uses free radicals to purify the body. Natural plant consuming antioxidants content is growing the interest for scientific research as well as industrial purposes. Pteridophytes (fern and fern allies) have drawn attention of plants seekers and horticultures since ancient period. Plant of Pteris vittata were collected from different geographical region of Uttarakhand Garhwal. The maximum yield of plant extract was found via the ethanol solvent i.e. 5.07-9.67%. DPV extract exhibited a maximum inhibition of 89.32 relatively closed to 91.96% inhibition of Ascorbic acid at the concentration of 0.1 mg/ml by DPPH radical scavenging assay method. The IC50 of the DPV extract and Ascorbic acid was found to be 0.543 and 0.495 mg/ml by same. DPV extract showed a maximum inhibition of 72.33 % relatively close to 77.42% inhibition of BHA at the concentration of 0.8 mg/ml by Hydrogen peroxide radical scavenging method. The IC50 value of the DPV extract & BHA was found to be 0.279 ± 0.005 mg/ml & 0.257 ± 0.002 mg/ml by same. DPV extract showed a maximum inhibition of 84.32% relatively close to 87.96% inhibition of ascorbic acid at the concentration of 0.8 mg/ml by Nitrogen oxide scavenging method. The IC50 value of the DPV extract & BHA was found to be 0.233 ± 0.002 mg/ml to 0.218 ± 0.006 mg/ml by same.

<i>In vitro</i> Antioxidant Activity of <i>Chrysophyllum albidum</i> Fruit

Chrysophyllum albidum (African star apple) is a tropical plant commonly found in Nigeria. It has acquired a reputation in folklore as a formidable therapeutic agent against yellow fever, malaria, diarrhea, vaginal and dermatological infections. This study was carried out to investigate the in vitro antioxidant activity of three extracts [aqueous (AE), methanol (ME) and petroleum ether (PE)] of the plant fruit using two antioxidant tests. The ferric ion reductive power and % H2O2 inhibition of the fruit extracts at 1 mg/ml concentration were evaluated, the result followed the pattern AE > ME > PE showing the strongest to the least strong antioxidant activity. However, the % H2O2 inhibition between the aqueous and methanolic extracts has no significant (p > 0.05) difference . A Comparative study reveals that the reductive power of ascorbic acid (1 mg/ml) is significantly (p < 0.05) higher than that of the fruit extracts except of aqueous extract. Though the % H2O2 inhibition of ascorbic acid was greater than all the extracts, a statistical difference (p < 0.05) was only observed in petroleum ether extracts of the fruit. This finding suggests that African star Apple has the potential to prevent lipid peroxidation and radical chain reactions. Hence, relishing the fruit as part of dietary intake and further exploitation as a therapeutic agent should be encouraged.

Kinetic spectrofluorimetric determination of trace ascorbic acid based on its inhibition on the oxidation of pyronine Y by nitrite

A highly sensitive spectrofluorimetric method is proposed for the determination of trace amount of ascorbic acid using a new indication. The method is based on the inhibition of ascorbic acid on the oxidation of pyronine Y (PRY) by nitrite. The detection limit for ascorbic acid is 0.012 μg ml −1, the linear range of the determination is 0.02–0.36 μg ml −1. Analytical parameters, such as reagent concentration, pH, reaction temperature and time, were optimized. The relative standard deviations of eleven replication determinations of 0.12 and 0.24 μg ml −1 ascorbic acid were 1.4 and 0.72%, respectively. This method has been used to determine ascorbic acid in pharmaceuticals, vegetables, fruits and soft drink with satisfactory results.

Corrosion inhibition of aluminium and zinc pigments by saccharides

Both aluminium and zinc pigments react in aqueous alkaline media (e.g., water-borne paints) with the evolution of hydrogen which can be measured gas volumetrically. The hydrogen corrosion of aluminium pigment can be inhibited with addition of the reducing saccharides fructose and mannose as well as with addition of the reducing ascorbic acid whereas the non-reducing saccharose did not inhibit this corrosion reaction. With increasing addition of fructose or ascorbic acid the hydrogen volumes evolved increase; this observation leads to the assumption that reaction products of aluminium and fructose or ascorbic are the actual corrosion inhibitors. The hydrogen corrosion of zinc pigment is inhibited by ascorbic acid only. So, the most efficient of the examined natural corrosion inhibitors both for aluminium and zinc pigment is ascorbic acid. But corrosion inhibition of ascorbic acid on zinc pigment is much less effective when compared to aluminium.

Ascorbic Acid Inhibition of Cytochrome P450-Catalyzed Uroporphyrin Accumulation

Previous studies on the mechanism of the uroporphyria caused by polyhalogenated aromatic hydrocarbons have indicated a key role of cytochrome P450 of the 1A subfamily in catalyzing uroporphyrinogen (UROgen) oxidation. Here we report that ascorbic acid (ASC) inhibits UROgen oxidation in primary cultures of chick embryo hepatocytes and hepatic microsomes from chickens and mice. In hepatocyte cultures, 0.15 mM ASC totally prevented the accumulation of uroporphyrin (URO) induced by treatment of cells with the combination of 3,4,3′,4′-tetrachlorobiphenyl (TCB) and 2-propyl-2-isopropylacetamide (PIA), but had no effect on the induction of protoporphyrin accumulation by PIA and desferrioxamine. However, addition of 5-aminolevulinic acid (ALA) to cultures treated with PIA plus TCB decreased the ability of ASC to prevent URO accumulation, suggesting that the effectiveness of ASC was dependent on the intracellular concentration of ALA or its metabolites. Similarly, when chick hepatocyte cultures were treated with TCB plus exogenous ALA to produce URO accumulation, the effectiveness of ASC was also less than when ALA was produced endogenously. Under this condition, addition of piperonyl butoxide, a P450 inhibitor, increased ASC inhibition of URO accumulation. ASC competitively inhibited the oxidation of UROgen by hepatic microsomes from chicks or mice treated with 3-methylcholanthrene (MC) with K i for ASC being about 0.1 mM. ASC prevented formation of a 500-nm absorbing compound, probably tetrahydrouroporphyrin, the first intermediate in UROgen oxidation. These results are consistent with ASC preventing URO accumulation in hepatocytes by competitive inhibition of the first step of UROgen oxidation and suggest a new physiological role of ASC, that of maintaining UROgen in the reduced state.

Inhibition of nitrosamine formation by ascorbic acid

Nitrosation occurs under a wide variety of conditions by reaction of most types of amines with any of a large number of nitrosating species. Nitrite can be formed in vivo via bacterial reduction of nitrate and by activated macrophages and endothelial cells. The mechanism of nitrite formation by mammalian cells is via enzymatic oxidation of arginine to NO followed by oxidation to N2O3 and N2O4. Nitrosatable amines are found in many foods and some, eg, dimethylamine, are synthesized in the body. Precursors of N-nitroso compounds are thus almost constantly present together under favorable reaction conditions in vivo and there is, consequently, considerable interest concerning possible human health risks arising from endogenous formation of this class of compounds. Among many nitrosation inhibitors, most attention has focused on ascorbic acid, which reacts with many nitrosating agents and which is virtually nontoxic. This presentation discusses the chemistry of ascorbic acid inhibition of nitrosation reactions.

Ascorbic Acid Inhibition of Nitrite-Induced Methemoglobinemia in Channel Catfish

Abstract Nitrite-induced methemoglobin concentrations were lower in channel catfish (Ictalurus punctatus) fed a diet containing 7,720–7,950 mg ascorbic acid/kg than in fish fed a diet containing 63 mg ascorbic acid/kg. The lower methemoglobin levels were evident after the fish were fed the higher ascorbic acid diet for 1 week. Fish were exposed to 2.5–5.0 mg nitrite-N/L for 22 h. Ascorbic acid exhibited a protective effect if fish were fed 48 h or less before blood was sampled, but no protective effect was evident if fish were last fed 65 h before sampling.

Ascorbic acid inhibition of alpha-adrenergic receptor binding

Relatively low concentrations of ascorbic acid inhibited the binding of the alpha-1 adrenergic antagonist [ 125I]HEAT ( dl-[β(3-iodo-4-hydroxyphenyl)-ethyl-aminomethyl]-tetralone) in rat submandibular gland and rat aorta. However, no inhibition was observed with this ligand in several other tissues, nor with several other ligands in these tissues. The inhibition observed was dependent on the concentration of both the ascorbic acid and the tissue. Maximal inhibition of [ 125I]HEAT occurred in submandibular gland at 10 μM ascorbic acid with B max values reduced 65% and no change in affinity. Ascorbic acid had a greater effect in assays in which less tissue was used, causing a 22% decrease in binding at 46 μg/ml, but a 48% decrease in binding at a tissue concentration of 12 μg/ml. EDTA prevented the loss of binding normally seen with ascorbic acid at a tissue concentration of 17 μg/ml. We suggest that, if an antioxidant is thought to be necessary in an assay system, its effects be carefully examined before routine use.

BETA-AMYLASE SULPHYDRYL AND DISULPHIDE GROUP REACTIONS. ADDITIONAL ASPECTS ON ENZYME INHIBITION BY ASCORBIC ACID

Cysteine, EDTA and certain other sulphydryl and chelating agents activated barley β-amylase at pH 7 but not at pH 4·35. Apart from oxalate and citrate the same reagents prevented ascorbic acid inhibition of the enzyme. A partial purification of the enzyme was effected on SP-Sephadex C-50 in the presence of mercaptoethanol and Ellman's reagent was reduced when incubated with ascorbic acid and the more active fraction which was isolated. When Ellman's reagent was added to an enzyme system containing additional copper which was incubated with ascorbic acid, a reduction of the synthetic disulphide reagent still occurred. An observable increase in absorbance at 360 nm was also noted in a similar enzyme system. The results suggest that the ascorbate free radical is readily attracted to the exposed disulphide bonds of β-amylase

Ascorbic acid inhibition of Campylobacter jejuni growth.

The inhibitory effect of ascorbic acid on Campylobacter jejuni is described. In vitro growth of clinical strains, as measured spectrophotometrically, was inhibited by 0.5 mg of freshly prepared L-ascorbic acid per ml. Alkaline-treated or aged L-ascorbic acid increased inhibition, as did copper; however, L-cysteine, L-cystine, and glutathione prevented inhibition. Biochemical analysis of the medium and cultures indicated that one or more of the oxidation products of L-ascorbic acid, e.g., L-dehydroascorbic acid or L-diketogulonic acid, were more effective inhibitors than was reduced L-ascorbic acid.

Ascorbic acid inhibition of Na,K-adenosine triphosphatase of rat forebrain without peroxidation of membrane lipids

Using reagents and membrane preparations from which contamination had been carefully removed, we found that ascorbic acid inhibited rat brain Na,K-ATPase without causing lipid peroxidation, unlike the conventional belief; the inhibition was prevented by catecholamines and EGTA. Ascorbic acid radicals, instead of active oxygen, may play a role in the inhibition.

Ascorbic acid inhibition of aromatase activity in human placental tissue

Ascorbic acid vitro causes inhibition of a biphasic type on the aromatase activity in human placental microsomes. Ascorbic acid, at low concentrations, partially inhibits (20–55%) the aromatase activity in a non-dose dependent manner (Type I inhibition). At higher concentrations of ascorbic acid, a profound inhibition (> 95%) of aromatase activity takes place (Type II inhibition). Under the experimental conditions chosen, molecular oxygen and NADPH required for the enzymatic synthesis of estrogens were not affected by ascorbic acid. Also, the inhibition of aromatase activity by ascorbic acid could be reversed by removing the ascorbic acid from the incubation medium. By increasing the concentration of NADPH a reversal of ascorbic acid inhibition of aromatase activity resulted and there was an increase in the pH of the incubation medium. Sodium ascorbate, in concentrations similar to those required to produce Type II inhibition by ascorbic acid, did not inhibit aromatase activity. The pH profile of the aromatase system has an apparent optimum at 7.5, and this enzymatic activity was extremely sensitive to changes in pH. The marked inhibition of aromatase activity by high concentration l of ascorbic acid (Type II inhibition) appeared to be related to these pH changes. We propose that the mechanism of Type II inhibition of placental aromatase by ascorbic acid vitro is due to disruption of the buffering capacity of the incubation medium which results in the concomitant lowering of pH. The Type I inhibition may be attributed to a non-specific mechanism since there is no correlation between the concentrations of ascorbic acid and the partial inhibition of aromatase activity.

Ascorbic acid inhibition of cyclic nucleotide phosphodiesterase acitivity.

AbstractLow levels of ascorbic acid reversibly inhibit mouse brain and beef heart cyclic nucleotide phosphodiesterase activity in vitro. Inhibition is noncompetitive with a Kt ≃ 10-4 M. Similar inhibition occurs with D-ascorbate but not with dehydroascorbate or metabisulfite. The kinetics of inhibition by ascorbic acid were similar for “high” and “low” Km cAMP phosphodiesterase and cGMP phosphodiesterase activity.