Science topics: ChemistryFree Radical Scavengers
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Free Radical Scavengers - Science topic
Free Radical Scavengers are substances that influence the course of a chemical reaction by ready combination with free radicals. Among other effects, this combining activity protects pancreatic islets against damage by cytokines and prevents myocardial and pulmonary perfusion injuries.
Questions related to Free Radical Scavengers
What is the impact of secondary reaction products formed from radical scavengers like tert-butanol, benzoic acid, [benzoate in alkalin media ], and nitrobenzene on the degradation rates of organic pollutants in alkaline media, and how do these products complicate the assessment of scavenger efficacy, particularly considering variations in pH that influence the stability and reactivity of these scavengers as both inhibitors and facilitators of degradation?
Hello to the entire RG community,
I have a question regarding the use of sample blanks vs. reagent blanks in colorimetric assays, particularly in the quantification of various phytochemicals in plant extracts (e.g., total flavonoids, total hydroxycinnamic acids) and in assays assessing the free radical scavenging capacity of these extracts.
The question is: When should we use a sample blank versus a reagent blank, and how can we distinguish between the two when encountering the common phrase "against a blank" in scientific papers?
For instance, if the plant extract concentrations we use exhibit a slight but persistent color that interferes with absorbance readings in the experiment, would it be appropriate to include a sample blank (i.e., extract at varying concentrations + solvent, but without the reagent responsible for the final colorimetric reaction) and subtract this absorbance from the sample's total absorbance? Or, even if the extract itself absorbs, no matter how diluted it is, should I forgo the sample blank and use only a reagent blank (i.e., all solvents but without the sample)?
Thank you for your insights.
I want to explore a technique to find reactive radical species in solid-phase pollutant degradation. For example, ESR, EPR, or transient absorption is used for the detection of reactive radical species in the liquid phase.
In an article, I found a scavenging study see the attached figure. Is there any other way to detect reactive radical species in solid-state photocatalysis? Moreover, is the data reliable like the liquid phase?
5-Methoxytryptophol as a hormone
I am performing DPPH test. My crude plant extract is showing higher percentage of free radical scavenging activity than standard BHT for each time. Is it okay or is there any problem? I'm not understanding it.
I am studying an aqueous photocatalytic system where superoxide radicals generate upon light irradiation. The system does not contain any biomolecules or bioorganisms. I need to study the effect of removing superoxide radicals, and for that, I need to add a scavenger. I searched in the literature but everybody has used benzoquinone for this purpose. The problem with using benzoquinone when I used it was it bound with my analyte so tightly that I could not separate the analyte by centrifuging or filtering. The literature does not provide the method of how they got rid of benzoquinone. Can you please help me with this if you have a similar experience? If not, please suggest to me some other superoxide radical scavengers that you have used in similar experiments. Thanks in advance.
I have quantified the free radical scavenging activity of plant extracts.
With excel calculate the EC50 value from the linear graph(y = mx + c) (%inhibition Vs. Concentration) where i substitute the y value with 50, and solve for x.
With Graphpad prism, i first transform the experimental data to logarithmic values. Thereafter, i normalise the data set (whereby the highest value was taken as 100 and lowest value as 0).
I then use the normalised data set to graph a non-linear regression curve fit, from were the IC50 is then generated by the program.
These two methods give me significantly different EC50 values. Which is the accurate approach to calculating the EC50?. Please help.
Need help regarding protocols
I am working with some oils which are not soluble in methanol, but soluble in IPA, etc. Can anyone help me the complete procedure regarding the use of IPA for DPPh assay to be done in microplate reader? also please help me with the complete protocol to be followed.
Thanks in advance.
I am looking for alkali stable radical scavengers.
I have a glycol solution of 80:20 ethyl diglycol:butyl glycol.
And want to add 10% KOH (so a waterless alkaline).
I have tried spiking the glycol solution with up to 2% BHT (butylated hydroxy toluene) before adding the KOH. As BHT is commonly used as antioxidant (radical scavenger)
However, it still seems unstable.
I was wondering if there are any Alkali stable radical scavengers or anything to supress discoloration and further (aldol) condensation of the present glycols.
I'm performing the antioxidant activity of essential oil by DPPH manner, and I was wondering about the value of IC50 it seems so high because that of reference which is ascorbic acid is around 0.018 mg/ml, whereas that of my sample is 2 mg/ml. There is a big difference!
When we can consider an essential oil as an antioxidant agent? Is there any intervale of IC50?
Is there any interest to say that this essential oil having an antioxidant activity?
I am looking for the reagent which can scavenge superoxide in living cells. Most of ROS scavenger, like tempol, inhibit not only superoxide accumulation but also reactive nitrogen spices (RNS). But I am actually looking at the effect of RNS in oxidative stress but not superoxide. Dose anyone know the cell permeable superoxide scavenger?
Please look at the image. It is showing DPPH free radical scavenging activity of something...
According to the image, what would be the IC50 value of Ascorbic acid used as a standard for that study?
Formula-
IC50 = (50-b)/a

Specifically am asking for antioxidant analysis( TAC, TFC and TPC) and free radical scavenging activity assays ( ADDH, FRAP AND BTS). it would be great if the reason could also be explained?
please i hope to now if the usage of diffuse basis function in calculs, would change the free radical scavenging capacities of biological molecules?
There are many essays to assess free radical scavenging activity in plant based preparations. How do I select the best method? What are the factors to be considered in selecting the most suitable essay?
I have determined the % Inhibition of DPPH free radical scavenging capacity. I have the absorbance value at 517 nm of my samples. Can I determine the Trolox Equivalent Antioxidant Capacity (TEAC) by plotting these same absorbance values in the standard curve prepared from different concentrations of Trolox?
A extract of a compound herbal drug was found to contain alkaloids, flavonoids, steroids, tannin and phenolic compounds and cyanogenic glycosides. It also contain considerable amount of antioxidants. DPPH assay revealed that the compound has potent free radical scavenging activity. Therefore, may it be efficacious on minimizing free radical induced tissue damage in normal ageing process?
I am currently working on prospects on molecular structure modification and tweaking of readily available compounds that are well-known good antioxidants in various in vitro assays. The goal is to modify the structures, synthesize them, and then assess the activities of the derivatives. Now, I am trying to find some understudied yet promising compounds that exhibit superior antioxidant capacity and has wide structural variability . I was wondering if anyone can suggest any understudied compounds and derivatives I can start with? Some literature and supporting articles would be a great help. Thanks
Vitamin C (ascorbic acid) is a water-soluble vitamin that is thought to have beneficial effects in patients with severe and critical illnesses. It is an antioxidant and free radical scavenger that has anti-inflammatory properties, influences cellular immunity and vascular integrity, and serves as a cofactor in the generation of endogenous catecholamines.1,2Because humans may require more vitamin C in states of oxidative stress, vitamin C supplementation has been evaluated in numerous disease states, including serious infections and sepsis. Because serious COVID-19 may cause sepsis and acute respiratory distress syndrome (ARDS), the potential role of high doses of vitamin C in ameliorating inflammation and vascular injury in patients with COVID-19 is being studied.
for example what is the difference between N-acetylcistein and BHT(BUTYLATE HYDROXY TOLOUEN)?
Antioxidants are chemical substances that can neutralize and scavenge the free radicals
Please be kind enough to clarify me what is the difference between assessing antioxidant activity and at the same time assessing free radical scavenging activity!
Looking forward for your kind response!
Thank You!
I have extracted methanol, ethanol, chloroform and water extracts of fenugreek and I have done DPPH and ABTS assays to determine free radical scavenging activity. However, I got different DPPH and ABTS results (inhibition percentages) for same concentration in same extract. Is that possible??
Hello, I am looking for a compound which could selectively quench reactive oxygen species while not quenching carbon centered radicals (for a polymerization reaction). Thanks a lot.
For doing DPPH free radical scavenging assay, I have used ascorbic acid as the standard. and took different concentrations (5,10,15,20,25 and 30 microgram/ml) for both standard as well as for plant extract. Above 30 microgram/ ml, the OD value for ascorbic acid remains to be same for all concentrations. For standard (Ascorbic acid) the % inhibition values are 24.04, 54.06, 86.68, 96.63, 96.78 and 96.93.And that for sample, values are 9.63, 17.34, 27.50, 33.51, 41.68 and 46.47. I plotted the scattered plot using % inhibition versus concentation (microgram/ml). Do I need to modify anything? Please help me!!
What scavanger can be used for detection of the Peroxy mono Carbonate [CO42-]
What is the meaning of IC 50 value in case of DPPH free radical scavenging method and how it is related with the antioxidant activity???
Hello all
I have an agent that increase the level of reactive oxygen species, I would like to do co-treatment with free radical scavengers (N-Acetyl-L-cysteine) to see if this will rescue cells from death. MY cells is at 5 x 10⁵ cells/ml.
For my agent I prepared working solution (20.4 µM) and then I to culture my cells in final concentration 0.4 µM, I add 20 µl of this working solution to my cells (1 ml). Now I need to do co- treatment with 50mM or 10mM of N-Acetyl-L-cysteine…my questions is how can I prepare that and how much do I need to add to my cells to get these concentration
If I follow this protocol: The antioxidant activity of the extracts was tested using DPPH as previously described with some modifications (Zhang et al., 2011). Briefly, the DPPH free radical scavenging activity of grain extracts was determined using a 2 × 10−4 M DPPH solution. Each sample (0.5 ml) was mixed with 4 ml 2 × 10−4 M DPPH in ethanol. The mixture was shaken, and then left to stand for 60 min in the dark. The absorbance was measured at 517 nm in a spectrophotometer. The absorbance of the control was obtained by replacing the sample with 80% methanol. The DPPH radical scavenging activity of the sample was calculated as follows:
% scavenged= [1- abs of sample/abs of control]x 100
I have done catalase, peroxidase, ascorbic acid and reduced gluthathione tests in antioxidant assays. I have done superoxide scavenging activity, hydroxyl radical scavenging activity and TBA test. I have calculated control, test and standard for all. How to calcuate them and plot them in graph?
what is the mechanism of superoxide anion free radical scavenging assay of plant extract?
Dear everyone,
Do you happen to know any carbon free radical scavenger stable at high temperature (~ 300 oC)? I am currently trying to determining whether a reaction is using radical mechanism. The reaction breaks a C-Cl bond and forms the C-H bond. I suspected the reaction undergoes the Carbon-chloride homolysis to form the radical, then the radical abstract a hydrogen from the solvent. To test it, I could think of using either a radical scavenger, or deuteride donor. Unfortunately, the reaction occurs only at high temperature. So I need to find something stable at that temperature. Anyone have any suggestions? Thank you so much
Dear All
I am studying the quenching effect in a system containing SO4 and OH radicals. I want to scavenge Oxygen using a liquid quencher since It will be sophisticated to pump N2 as an oxygen quencher. I have read that hydrazine can quench oxygen, but I am inquiring if it can also scavenge SO4 and OH radicals or not. If it can quench them, Is there any other alternative oxygen quencher that can scavenge oxygen only or what is the reaction rate?
Thanks in advance
Regards,
I'm looking for a solid OH radical scavenger, not liquid.
Are there any effective solid OH radical scavenger??
I am embarking on an exploratory research project on secondary metabolites of marine organisms particularly on sea stars and brittle stars. What natural products should I consider first? Im looking for a list of natural products and various methods I can use to identify and quantify them. I am planning to do zoochemical analyses, in vitro antioxidant activity, and cytotoxicity.
I hv carried out dpph assay on sargassum extract and found out following result..can someone please tell me ic50 value of it and whether it is correct or should i have to repeat the expt again..? Thankyou

Dear All
I want to measure sulfate radicals concentration using dimethyl sulfoxide. Please, can you provide me with a reference for measurement of sulfate radicals using dimethylsulfoxide.
Regards,
We have ROS such as O2•−, OH•, H2O2,and 1O2. The ROS scavengers are NADPH, Uric acid, Vitamin A, Vitamin C, Vitamin E, Glutathione, Beta-carotene and polyphenols, etc. In these, which is more powerful scavengers to ROS. Is there any selectivity? what is the order of scavenging ability of above bio-molecules?
Please share your knowledge and Thank you in advance.
the results I got are oppose to each others ... hydrogen peroxide scavenging decreased and the inhibition activity of DPPH increased .. Is there a relationship between these methods?
I am planning to immobilize anti-oxidants like Gallic acid in a nanocarrier with targeting moiety decorated on the surface of the nanocarrier. If i link the anti-oxidant with a covalent bond is it still possible for the nanocarrier to exert free radical scavenging properties once it reaches the target site or is it essential to release the anti-oxidant cargo to exert free radical scavenging properties at the target site.
AAI/AAU is used for calculation of DPPH free radical scavenging assay. Its a new method for standardizing DPPH results.
Please share you experiences about the best method to determine radical scavenging on natural product samples.
The way to determine DPPH radical scavenging activity has been described in so many papers, but I need a protocol with more details.
I performed hydroxyl radical scavenging by the method of Halliwell et al 1987. According to literature, TBA makes a pink color with the reaction product (MDA) after degradation of 2- Deoxy ribose. But I obtained a yellow color after the completion of the test and therefore I am unable to calculate radical scavenging activity. Please suggest solutions for the problem.
The ABTS•+ radical cation was produced by reacting 7.4 mM ABTS and 2.6 mM potassium persulfate solutions (1:1) and stored in the dark at room temperature for 12 h and then diluting with methanol to get an absorbance of 1.1 ± 0.02 at 734 nm. Plant extracts (150µl) at 200µg/ml was mixed with ABTS•+ solution (2850 µl) and then incubated at dark for 2 hr. Absorbance was found to be 0.218 at 734nm. Trolox standard is prepared from 50 to 600µM. The equation of trolox is y = -0.0010x + 0.6713, R2 = 0.9968. Most of the paper followed in the Re et al (1999) was expressed in % inhibition or IC50 or trolox equivalent and its ABTS•+ solution was diluted to 0.7 absorbance. But I don’t find any paper expressed in % inhibition for the protocol which I have followed. Can it express in % inhibition using the same protocol or it should express as µM TE/g? If it should express in trolox equaivalent, then how can it calculate? Please help me
Good day. I am using the DPPH free radical scavenging assay to determine antioxidant activity in tomatoes. I have carried out the extraction, read the absorbance and calculated the scavenging activity in percentage (%). I have also read the absorbance of various concentration of of ascorbic acid and plotted the percentage scavenging effect against concentration. With what formular do I convert or express my answer in mg AA/100g?
Different antioxidant assay have different mechanism as well give different activity. How can we decide which method is suitable for free radical scavengers?
What will happen on IC50 if I'll prefer to use 0.002% of DPPH instead of 0.004 % of DPPH as the free radical scavenging method? Will IC50 of 0.002 % DPPH be decrease with comparison to the IC50 of 0.004 % of DPPH ?
i want to know the scavengers of hydroperoxide radical. Who knows about that?
Recently I’m working on hydroxyl radicals detection and I use pCBA as a probe. But here is the problem, I can’t dissolve pCBA in water! I understand that pCBA is insoluble in water but there were many research work have been done before but the author didn’t mention how to solve the the dissolve problem. I tried to raise the temperature to 80℃ but the pCBA didn’t dissolve, and I put NaOH to react with pCBA hoping to form soluble salt but it didn’t work at all! I really confused why the Na- pCBA can’t dissolve in water! In short, I’m confused about how to dissolve pCBA in water, is there anyone facing the same problem? Welcome to share! Thanks in advance!
What is the meaning of IC value in case of DPPH free radical scavenging method. Say for the IC50 value of the _ _ _ extract and and ascorbic acid were _ _ _ microgram/mL. Then, what is IC here ? and how can I calculate it ?
what is the standard DPPH free radical scavenging activity for plant extracts? i am working withmedicinal plants for the estimation of their antioxidant properties and i have read many research papers for various methods for antioxidant estimation. ther are many different methods for the DPPH method. Can anyone help me to solve this problem?
Can anyone explain the importance of using a positive control (eg quercetin) and a negative control (methanol) while calculating the DPPH free radical scavenging activity?
The formula that I am using for my extracts is as follows:
% Inhibition = [(A0-A1)/A0] × 100
Where A0 is the absorbance of the control; A1 is the absorbance of test samples.
We are preparing chitosan encapsulated naringenin. For that we need to know the mode of action of naringenin. It would be greatly helpful if anyone tells the answer with reference.
I am calculating DPPH inhibition data. I have graphed my DPPH inhibition against concentration and I am trying to calculate the IC50 for my samples. However, when I calculate the IC50, using the equation fo the line (intercept=0), I find that compounds with highest %DPPH inhibition have highest IC50 values. Surely this is incorrect? Does anybody know what I am doing wrong?
We have different medicinal plant extracts. So please suggest the recent trends used for free radical scavenger activity.
There are quite a number of methods to evaluate the in vitro antioxidant activities. Can you please suggest me the best and the most effective method?
What role does solvent play in extracting antioxidants from natural sources? Please suggest.
I am working with a phenolic compound that may act as a free-radical scavenger within macrophages, reducing the initiation of apoptosis. I have seen reports that test the free radical scavenging capacity of food products, but I don't that these will be useful in my case, since I am interested in the intracellular compartment. Thanks!
Antioxidant property of polyphenols could prevent brains from free radical attack to cells and scavenge them.
Can anyone list the in vitro radical scavenging assays with same substrates (involved in the reaction) so that i can avoid those non-substrate specific assays?
Can anyone tell me about the IC50 standard for NO that our sample (plant extract) is active as a radical scavenger (see link below)
Dear all,
Can anybody explain to me the exact difference between FRAP analysis and Free Radical Scavenging analysis? Do they measure the same thing? What's the difference between them? Thank you so much.
In many papers, the researchers use both of DPPH and OH radical scavenging. But why should we use both of them?
What is difference between the principle of 2 methods?
The IC50 value of ascorbic acid reported in research papers differs significantly. I have used DPPH assay, galivonoxyl free radical scavenging assay and ferric ion scavenging assay for evaluating in vitro antioxidant activity of plant extracts and used ascorbic acid as a standard for the same. Could you kindly help me to know the exact IC50 value of this compound in all the above mentioned assays?
Is it possible to understand using PetroOXY whether antioxidants are free radical terminators or oxygen scavengers?
DPPH, a free radical, is used to measure potential to scavenge free radical. Is there any effect of pH as well as temperature on the experiment?
This question was raised by a reviewer. Please help me to answer this in a scientific way,
Is there a default value because I found the absorption rate sometimes fluctuates.
Please share your experiences about the advantages and disadvantages of radical scavenging methods from medicinal plants.
I was wondering if anyone could point me to literature or maybe some knowledge with regards to how I should prepare my samples prior to running a DPPH assay for measuring antioxidant activity?
I have Joshanda tea, green tea and lyons tea, I'm just unsure on how to begin preparing my samples and have been hitting a wall with regards to searching online.
The oscillations in the Bray-Liebhafsky reaction (hydrogen peroxide decomposition catalyzed by iodate and iodine in acidic solutions) are strongly perturbed by oxygen, a product of the reaction. We (G. Schmitz & S. Furrow) believe that the oscillations are explained by non-radical reactions but that the perturbing effect of oxygen is the result of radical reaction. In order to obtain "clean" oscillations, we are looking for a radical scavenger that does not react with the iodine compounds involved in the oscillations, IO3, IO2H, IOH and I2. Who has a suggestion?
What is the effect or the mechanisms of activities of ferrocene compounds,(ferrocenium) free radical on breast cancer cells and on normal cells?
Can the repetition of assays of same substrates be avoided?