ORGLIST:Nature of the TBA Chromogen

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From: Ismail, Fyaz (F.M.Ismail$##$livjm.ac.uk)
Date: Fri Mar 12 2004 - 12:55:57 EST


Dear Jacob,

The identity of the thibarbituric acid complex (Kishida et al. 1993) has been recently (re) investigated using modern analytical methods especially MS and MS-MS. (see Jardine et al. 2002). Briefly, the thiobarbituric acid reactive substances (TBARS) assay does, indeed, detect breakdown products of lipid peroxidation. Commonly, malondialdehyde is formed as a result of lipid peroxidation and reacts with thiobarbituric acid to form a pink pigment (absorption maximum at 532 nm).

Importantly, other compounds also react with thiobarbituric acid to form coloured species that can interfere with this assay, but little is known about these interfering species. Jardine et al. have used LC-MS and MS-MS to study the structures of the pink adduct as well as a common unstable yellow interference compound, which absorbs at 455 nm. They found that the presence of barbituric acid impurities in the thiobarbituric acid reagent was found to produce 1:1:1 thiobarbituric acid/malondialdehyde/barbituric acid and 2:1 barbituric acid/malondialdehyde adducts that absorbed at 513 and 490 nm. Hence, before you utilise thiobarbituric acid, it should be thoroughly purified before use.

It should be noted that some of the chromogens fade over time. An older paper by Pegg et al. (1992) reveals NMR and stability data for some of the chromogens produced during this widely used but imperfect indicator of lipid peroxidation.

Kindest Regards,
Fyaz
Medicinal Chemistry Research Group,
Liverpool

References
Jardine, D.; Antolovich, M.; Prenzler, P. D.; Robards, K.; Liquid Chromatography-Mass Spectrometry (LC-MS) Investigation of the Thiobarbituric Acid Reactive Substances (TBARS) Reaction
J. Agric. Food Chem. 2002; 50, 1720-1724.

Kishida, E.; Kamura, A.; Tokumaru, S.; Oribe, M.; Iguchi, H.; Kojo, S. Re-evaluation of malondialdehyde and thiobarbituric acid-reactive substances as indices of autoxidation based on oxygen consumption. J. Agric. Food Chem. 1993, 41, 1-4.

Ronald B. Pegg, Fereidoon Shahidi, Chet R. Jablonski; Interactions of sulfanilamide and 2-thiobarbituric acid with malonaldehyde: structure of adducts and implications in determination of oxidative state of nitrite-cured meats
J. Agric. Food Chem. 1992, 40, 1826-1832.

____________________________________________________________________________________________________________

http://www.staff.livjm.ac.uk/pacfisma/

Dr Fyaz MD Ismail
The Medicinal Chemistry Research Group
The School of Pharmacy and Chemistry
Liverpool John Moores University
Room 221C James Parsons Building
Byrom Street
Liverpool L3 3AF

Telephone: +44 (0)151 231 2231.
E-mail: f.m.ismail$##$livjm.ac.uk

 --- Jacob Zabicky <zabicky$##$bgumail.bgu.ac.il> wrote:
> Malondialdehyde (MDA) and thiobarbituric acid (TBA)
> react to give a dye
> with absorption maximum at 532 nm. This reaction is
> the basis of quite
> a popular assay for assessment of lipid
> deterioration by autoxidation,
> with thousands of papers referring to it. I searched
> in vain many
> sources looking for the structure of the dye. Does
> anybody know where
> to look for that?
>
> All the best,
>
> Jacob
>
> Prof. Jacob Zabicky
> Institutes for Applied Researcfh
> Ben-Gurion University of the Negev
> P. O. Box 653
> Beer-Sheva, 84105
> Israel
> -------------------------------------
> zabicky$##$bgumail.bgu.ac.il
> Tel. +972-8-6461271
> Fax. +972-8-6472969
> -------------------------------------
> Private: P. O. Box 12366
> Beer-Sheva, 84863
> Israel
> Tel. +972-8-6496792

        
        
                
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