Talk:Vitisin A (pyranoanthocyanin)

Chemical structure

There is a need to improve the structure image. There are 3 issues that I can see:

There is an oxygen atom that has 4 bond (it can only have a maximum of 3)
The configuration of anomeric centre of the sugar is currently not clear. Is it supposed to be a single anomer or is it a mixture of anomers?
The configuration of the 5-position of the sugar is drawn in an unconventional way (for a traditional chair representation the group is neither equatorial or axial. --The chemistds (talk) 16:07, 23 April 2011 (UTC)[reply]

I have replaced the image. Can you check that it looks right to you now? -- Ed (Edgar181) 13:44, 23 May 2011 (UTC)[reply]

Thanks for tackling this - It generally looks pretty good. My only question is, why is the molecule shown as protonated? I would always expect to see the neutral molecule - unless the article is specifically refering to a protonated or deprotonated form. --The chemistds (talk) 16:05, 23 May 2011 (UTC)[reply]

Can I ask which source you used as the basis for tidying up the structure? --The chemistds (talk) 16:13, 23 May 2011 (UTC)[reply]

It is odd, but the name "Vitisin A" seems to refer specifically to the protonated form. This is the structure depicted by Chemical Abstracts, the source I used for my structure. -- Ed (Edgar181) 16:17, 23 May 2011 (UTC)[reply]

Chemical structure again

The image File:Vitisin A pyranoanthocyanin.png does not appear to be vitisin A. The structure matches the one in the reference given for the image (Fulcrand et al, 1998 A new class of wine pigments generated by reaction between pyruvic acid and grape anthocyanins. Hélène Fulcrand, Carime Benabdeljalil, Jacques Rigaud, Véronique Cheynier and Michel Moutounet, Phytochemistry, Volume 47, Issue 7, April 1998, pp. 1401-1407, doi:10.1016/S0031-9422(97)00772-3). But that article never refers to the chemical as vitisin A. File:Vitisin A.svg correctly depicts the structure given by chemical abstracts, correctly matches the structure given in a number of other references (for example: Effect of Storage Temperature and Pyruvate on Kinetics of Anthocyanin Degradation, Vitisin A Derivative Formation, and Color Characteristics of Model Solutions. Romero, Concepcion; Bakker, Johanna. Journal of Agricultural and Food Chemistry (2000), 48(6), 2135-2141.) and matches the rest of the data in the chembox, so I have reintroduced that image. -- Ed (Edgar181) 14:23, 15 June 2011 (UTC) File:Vitisin A.svg is the originally proposed structure. File:Vitisn A pyranoanthocyanin.png is the revised (correct) structure. See Vitisin A Content in Chilean Wines from Vitis vinifera Cv. Cabernet Sauvignon and Contribution to the Color of Aged Red Wines, J. Agric. Food Chem. 51 6261, doi: 10.1021/jf0346612. Also note that ref. 4 concluded that under neutral conditions (pH 7) vitisin A most likely exists primarily as a quinonoidal tautomer of File:Vitisin A pyranoanthocyanin.png. 69.72.92.105 (talk) 00:49, 23 September 2014 (UTC)[reply]