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2‐thiobarbituric acid test for lipid oxidation in food: Synthesis and spectroscopic study of 2‐thiobarbituric acid‐malonaldehyde adduct
Author(s) -
GuzmánChozas Matías,
VicarioRomero Isabel M.,
GuillénSans Remedios
Publication year - 1998
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-998-0321-3
Subject(s) - thiobarbituric acid , adduct , lipid oxidation , chemistry , food science , tbars , organic chemistry , biochemistry , antioxidant , lipid peroxidation
Synthesis, purification, elemental analysis, and spectroscopic studies were undertaken to characterize the structure of the red adduct 2:1 thiobarbituric acid (TBA)‐malonaldehyde involved in the evaluation of oxidative rancidity in fats and oils. Thin‐layer chromatography, infrared and ultravioletvisible absorption, 1 H ( 1 H NMR) and 13 C nuclear magnetic resonance (NMR) spectra were used. A yield of 93% was obtained in the synthesis. The results of elemental analysis agree with the formula for the chloro‐monohydrated form, C 11 H 11 N 4 O 5 S 2 Cl. Three characteristic absorption maxima at 532, 310, and 245 nm, respectively, were shown in acid aqueous medium (pH 2.9). The characteristic vibrations assigned to the ‐NH, ‐OH, C α H (exocyclic) and ‐C=S groups were confirmed in the infrared spectra. There was no evidence of thioenolization. 1 H NMR data at δ 5.10 (‐CONH‐ group, H 2 O and HCl molecules); δ 11.54 (‐OH group of keto‐enol tautomer, ‐NH group); and δ 176.4 (‐CONH‐ group) also were observed. The experimental results obtained were consistent with the existence of two spectral equivalent tautomeric structures. The colored adduct was compared with other TBA‐aldehyde compounds.