By Anonymous on Friday, July 2, 2004 - 05:57 am:

Hello

I have to identify major antioxidant peaks in HPLC-DAD chromatograms in order to follow their presence or absence in extracts coming from supercritical CO2 .

We don't care about structure (this task belongs to another partner), but just on knowing which peaks will we have to take into account in our chromatographic runs.

My question is very simple:
is spiking with ABTS enough to my purpose? (for example, a few drops/microliters of a ready ABTS liquid solution added to purified extracts before HPLC for comparing with non-spiked chromatograms)

Thank you in advance

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By Constantin Sychov on Saturday, July 3, 2004 - 01:47 am:

Your question is absolutely unclear. What do you mean? I can tell about main groups of antioxidants in plant extracts and how to measure them by HPLC-DAD.
What is ABTS?

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By Anonymous on Monday, July 5, 2004 - 02:15 am:

ABTS is a compound which gives free radicals, so when you add this to a natural extract, where there are antioxidants but you don't know which is the corresponding antioxidant peak, you should be able to see a change in the intensity of antiox peaks.
I finally found the answer to my question: it is yes.

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By HW Mueller on Monday, July 5, 2004 - 11:39 pm:

What do you mean by "gives free radicals"?
ABTS is apparently an oxidizing agent which is known to be capable to reduce known natural antioxidants (reducing agents)?
If so, you can easily and quickly add to the horrendous pseudo-science surounding free radicals in living things. Just a few examples: If your ABTS concentration is not right you may not have a reaction, even in presence of antioxidants, or, contrarily, a reaction with a substance that can not be regarded as an antioxidant in a natural setting. Your antioxidants may have been oxidiced by the oxydizing gent O2, prior to adding ABTS. You could have lots of antioxidants present which do not chromatograph......

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By Anonymous on Tuesday, July 6, 2004 - 07:15 am:

I apologize for my bad English, by "gives free radicals" I meant kind of "reacts with antioxidants".
Regarding your explanation, I don't totally agree, because the only difference between my 2 extract fractions is the presence or not of ABTS (I just divide my final extract in 2 halves), so oxydizing agents will be the same in the 2 matrixes, except ABTS. Thus, if there are peaks which decreases or disappear in the "WITH ABTS" chromatogramm, these peaks should be my antioxidants, which have reacted with the ABTS (if it is enough concentrated)

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By HW Mueller on Wednesday, July 7, 2004 - 12:12 am:

Just one more point: Do you know or do you assume that your ABTS, whatever that is, removes only substances from your fractions which behave as antioxidants in nature?

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By anonymous on Thursday, July 8, 2004 - 03:02 am:

I hope!!
I mean, I have already thought at this possibility, that's, as we say in Spanish, "la pregunta del millón" (the golden question???).
ABTS is actually used to mesure antioxidant activities, so I hope that its main reactivity feature will be that one... so, I assume & I hope!!
Thank you for your attention