I am about to evaluate antioxidant activity of my aqueous crude extract by invitro method i.e Hydroxyl radical scavenging assay and hydrogen peroxide scavenging assay.i got test and control absorbance values but the control value is less so when i am calculating the percentage purity negative values are coming.can anyone suggest me what to do?
I don't know enough to answer. Purity of what?
what is your system?
scavenging of OH radicals is a matter of concentration since almost all compounds react with them with similar rate constants.
We have observed such negative effet using low concentration of plant extract when carying out antifungal test. May be you could try a higher concentration of your plant extract and apreciate it antioxidant . If the result is not conclusive , then you could check another hypothesis
The challenge basically comes from not being careful in handling the reagents used for the analysis. I think the reagents especially the hydrogen peroxide should be prepared fresh prior to its addition and it should be used or added immediately
In addition to the answer of Ajaegbu Eze; check out if your reagents are not too old. Usualy, old reagents bring out results opposite to that you are expecting
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