The antioxidant activity of the control ascorbic acid was different from the value reported in the literature (IC50, 9.3 microgram/ml, 66.2 microgram/mL, etc…). Please any one explains the discrepancy between various data.
yes, i was going to say the same
it depends on the conditions in which you're working, and mainly on the final DPPH concentration
and it depends also on the solvent in which you prepared your DPPH (etanol or methanol)
The antioxidant activity of IC50 value at 50 percent of the concentration in the y axis. Ascorbic acid used as a standard. The IC50 values are different from the plant extracts.
I think the IC50 value of a sample depends on the initial conc of your DPPH solution. Before doing the assay always standardize the DPPH control absorption to 0.7 or something. if your control absorption changes significantly, then the IC50 value of a sample will also change each time. Check whether they have mentioned the control absorption. In addition, the results will also change based on your working environment.
If IC50 value obtained from DPPH assay is more than ascorbic acid..what does it mean?? what is the standard IC50 value of ascorbic acid???
DPPH is 1-electron oxidant while ascorbic acid is 2-electron reductant. "The standard IC50 value of ascorbic acid" does not exist.
When DPPH assay is performed for standards, we first take 1 mg/ml of Ascorbic acid which is a stock from that we take 100 microliter and dilute it with 900 microliters of methanol or ethanol. Then we get 100 micrograms/mL. On performing the assay we get maximum scavenging of say 87 % at 16-20 micrograms concentration and when we do the DPPH assay of crude extracts we get maximum scavenging at say 250 micrograms. THe IC 50 of standard will be 9-10 micrograms and for the crude it will be 120 microgram how it is possible to plot and compare the crude with standards. Is it mandatory to get maximum radical scavenging / IC 50 close to the ascorbic acid.
Environmental condition like temperature can affect your result since DPPH is involved
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