Dear Mohini Tayade ,

The proper concentration of your sample is important for DPPH radical scavenging activity assay. If your antioxidant activity is strong, when you perform this assay, you would find that all free radicals are eliminated and the results cannot be compared. Therefore, you must carry out some experiments in advance to find out what concentration is appropriate. Under this concentration, the clearing ability is moderate. It will neither remove all of it, nor remove only a small amount.

Hope this could help you.

Best regards,

Weihao

Thank you Weihao

weihao, can you tell me why the absorbance increase instead of decreased in the DPPH assay. I have taken 1/50 dilution of my drug but the result showed increased absorbance instead of decreased

Dear Mohini Tayade ，

I think there may be two reasons for this phenomenon. First of all, drugs diluted 50 times may have lower antioxidant capacity, and you should expand the concentration of the drug. Secondly, judging from the increase in the absorbance you showed, your drug may have a specific color. Therefore, you should use a solution of the drug at this concentration as a blank to correct the absorbance. Hope these can help you.

Best regards,

Weihao

Simple, you need a dilute concentration so you can have a measure of how much dpph is remaining after some of it (dpph) is scavenged and not get the situation where all are scavenged with none remaining. If all are scavenged, the question will be......is it possible that a lower concentration could've done the same total scavenging? Perhaps some amount of the drug had no more dpph to scavenged. Controlled dilution is very important.

@Mohini Tayade's second question......I agree with @Weihao's recommendation. Please have a look at the colour of the drug prepare a blank at that same concentration if necessary