User talk:Alexander N. Alexandrov

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• Hi!

Im very glad to see the place where is no spammers, no child/pubert wandalism, no gay-activist and no pseudoscience (kweer-researchers and so on)!

:-) Alexander N. Alexandrov 02:56, 30 November 2007 (CST)

Oxidant/prooxidant balance in relation to vitamin C

Hi Mr. Alexandrov,

It's nice to receive a visit on the vitamin C page from a specialist with a background like yours. I'd like to understand more fully your intervention:

In oxidation process the molecule of vitamin C step by step oxidazed with built up some active prooxidant substances.

I understand that the antioxidant machinery is complex, that not all antioxidants are chain-breaking, and as a result, the provision of an antioxidant can result in a build-up of oxidants elsewhere. To illustrate this, SOD will raises H2O2, which can eventually lead to toxicity, such as in the case of trisomy, where the gene for SOD is overexpressed due to the extra chromosome. However, in the case of vit. C, not that I'm unaware of issues related to prooxidant phenomena, but it requires much details and in vivo analyses. Saying that ascorbate is used in conjuction with transition metals, in vitro, to expreimentally generate free radicals (Fenton reaction), can be relevant in vivo sometimes, but we have to remain careful about how we extrapolate from in vitro to in vivo, right? In any case, I encourage you to provide more infos and explanations, never mind about the references, I'll get them.

--Pierre-Alain Gouanvic 12:28, 2 December 2007 (CST)

Hi dear Mr. Pierre-Alain!

You completly right, we must collect references for pruve all sentences :-)

- after wikipedea I'm lost some scientific reflexes :-)

Fenton reaction - is in vitro modeling, but in this moment I can't find ref to in vivo model...

so You can hide my post - up to date we can find corectly references for it :-)) Alexander N. Alexandrov 02:23, 3 December 2007 (CST)

• I'm look in Google scholar and first articles are fully adequate - e.g.

some of the discrepancies can be explained by flaws in experimental design and methodology. These and other important issues discussed here need to be addressed in future studies of the role of vitamin C in oxidative damage.—Carr, A., Frei, B. Does vitamin C act as a pro-oxidant under physiological conditions? and (text not available), Proc Natl Acad Sci U S A. 2007 May 22;104(21):8749-54. Epub 2007 May 14 Ascorbate in pharmacologic concentrations selectively generates ascorbate radical and hydrogen peroxide in extracellular fluid in vivo.

Environmental Toxicology and Pharmacology

Volume 11, Issues 3-4, July 2002, Pages 321-333

:-) Alexander N. Alexandrov 04:41, 3 December 2007 (CST)

The pro-oxidant chemistry of the natural antioxidants vitamin C, vitamin E, carotenoids and flavonoids (Ivonne M. C. M. Rietjens, , a, b, Marelle G. Boersmaa, Laura de Haana, Bert Spenkelinka, Hanem M. Awada, Nicole H. P. Cnubbenb, c, Jelmer J. van Zandena, b, Hester van der Woudea, b, Gerrit M. Alinka, b and Jan H. Koemana)

Really in last time this thesis more and more right :-) Alexander N. Alexandrov 05:56, 3 December 2007 (CST)

ascorbic acid

Hi Mr Alexandrov. I removed the redirect at ascorbic acid per your comment at talk: vitamin C. So now you need to join the write-a-thon, because the new article needs content! Aleta Curry 15:55, 4 December 2007 (CST)

Ok! Do it together! Alexander N. Alexandrov 02:39, 5 December 2007 (CST)

Welcome aboard, feel free to ask for more info if you need it. Chris Day (talk) 03:10, 5 December 2007 (CST)