Does anyone know how to interpret DPPH results made on liquid extracts ?
I tested some liquid extracts (seems like a tincture) with DPPH, I have 30% inhibition of DPPH at a concentration of 750 µg/mL. This value is pretty high when compared to ascorbic acid that might have 30 % of inhibition at 5 µg/mL ; but my compounds are diluted since it's a liquid sample. How can I exploit this result ? If I have Something like 90% of solvant in my sample, can I say that I have 30% inhibition at 90% of 750 µg/mL ?
Otherwise, mais I have divide the concentration used in the test by the dry matter content ?
Thanks !
Does your liquid extracts were sometime earlier a powder?
If does not, you can express then as volume of your extract to reach x% of inhibition. Other ideia is to compare with a analytical curve of ascorbic acid and express the results as equivalents of ascorbic acid ( xx mg of AA/L).
I will be glad to help you with other doubts, if necessary
Yes I agree with Bruno Luis Ferreira
You can also dry the known volume of sample and measure the quantity of solutes in your extract.
The antioxidant activity of a liquid extract or slid sample can't be characterized by a single number. You have to know the total antioxidant capacity (so called TAC) in ascorbic acid (or Trolox) equivalents and how quickly these antioxidants scavenge reactive nitrogen and oxygen species (RNOS). My advise: Do your job professionally . Otherwise it would be a waste of time. In any case, learn and read before doing experiments.
Bruno Luis Ferreira thanks for the answer. I often read results as equivalent of ascorbic acid or equivalent of trolox for ABTS assays, but I don't really understand how to obtain this result.
I have to do my test with ascorbic acid, plot the concentration / % inhibition, and then I'm not sure : I measure the % of inhibition of my liquid sample (with or without dilution) ? Then I read on the graph the concentration of ascorbic acid equivalent to that % of inhibtion?
Manoj Saravana Guru Mohan Ram yes, we are thinking about express as a dry matter content equivalent if no solution .
Yurii V Geletii what are the main difference between TAC and DPPH assays ? We don't really know if our extracts have an activity, we only do some preliminary tests before going forward.
"the total antioxidant capacity (so called TAC)" GOOGLE for this term.
See as an example
Geletii, Y.V., Balavoine, G.G.A., Efimov, O.N. et al. Russian Journal of Bioorganic Chemistry (2002) 28: 501. https://doi.org/10.1023/A:1021249717025
You can express your results using ascorbic acid or trolox equivalents, if you are testing in samples of fruit for example, I strongly recommend the use of ascorbic acid.
To obtain this type of data you will need to perform your DPPH protocol in an analytical curve of ascorbic acid solutions, increasing the concentration (for instance, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 mg/L of AA), then you will compare your results (Abs or even %inhibition) with your AA analytical curve. Each point of AA will return a result, so you just need to plot AA concentration vs Abs and build a regression curve on a math software, in addition to that, you will obtain an equation to calculate your sample results.
* if you are working with different extracts of different concentrations, %inhibition won't work for comparison purposes.
I dont have the DPPH protocol in english here in my laptop, I will try to find and post here later
Bruno Luis Ferreira , thanks a lot, I think our protocol is fine now !
Thank you a lot for your answer, it helped me to clear some confusions that I had.
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