hi,
I have a question about the preparation and procedure of the DPPH assay in onions.
I already have some results with a 0.1 mM DPPH solution:
%DPPH radical scavening of Ascorbic acid
5 uM 5,984876429 %
7.5 uM 15,27111767 %
10 uM 33,89893028 %
15 uM 55,30247141 %
20 uM 76,65068241 %
but with my onion extracts I had very high values:
%DPPH radical scavening of onion samples
Onion yellow/A 54,11059457%
Onion yellow/B 56,16589185%
Onion Red/A 103,3887937%
Onion Red /B 103,5600685%
I took the concentration of 0.1 mM from a wheat protocol. But in a couple of scientific papers I've noticed, that the usually used DPPH concentration for onion extract is 0.6, 0.4 or 0.2 mM. But I´m not sure which of them should I take and why? Could somebody explain the logic behind it i.e. why these exact values are used?
Hi, please let me mention something about antiox. activities.
First, your research material is an onion solution. this is a crude extract. Activity of pure compounds and that of crude extracts are not comparable !!
Next, you should carculate EC50 of your extracts to compare activities of your materials. Or you should make standard curves using ascorbic acid, trolox..... to express your data as compound-equivalent values.
Anyhow, you can prepare some dilutions of your onion solutions, then please evaluate them.
DPPH concentration is not critical matter for your research.
Suggestion 1: You should consider the concentrations of ascorbic acid from
from 0 uM to a larger than 20 uM, which will scavenge 100% of DPPH's absorbance.
Suggestion 2: You must dilute the concentration of onion extract. This might give you a value between 0 -100%. Then the results of the onion extract would be comparable to that of the standard i.e. ascorbic acid.
NB: The final concentration of DPPH is 0.1 ~ 0.2 mM is OK.
Good luck!
You should use different concentrations for each extract sample to get lower-higher scavenging activity of these concentrations like you did for the standard. Calculate the IC50 value for both standard and sample and then compare them. Oh, do not forget to use duplicate determination...
Best of luck..!
- Badges
- Science topic