The wide diffusion of 2-thiobarbituric acid (TBA) in the scientific literature is due to the TBA assay, or TBA test, which has been employed in the determination of autoxidative alterations of fats and oils. Two processes occur in autoxidation, generally: the free radical and the photo-oxidation mechanisms. The better studied is the free radical mechanism. The hydroperoxiepidioxides and bicycloendoperoxides are malonaldehyde (MDA) precursors. The absorption spectrum obtained with oxidized fatty foods is like the spectrum obtained when TBA and MDA react. However, during the secondary phase of the autoxidation process other aldehydes (alkanals, 2-alkenals, dienals) are formed which react with TBA, and they are responsible for off-flavors. Three kinds of pigments (yellow, orange, red adducts) are involved. Also, aromatic aldehydes, which constitute the flavor profile of diverse fruits and essential oils, form with TBA the characteristic arylidene-2-TBA acids. Other substances, such as ketones, ketosteroids, acids, esters, sugars, imides and amides, amino acids, oxidized proteins, pyridines, pyrimidines, and vitamins can react with TBA; they are named TBARS (substances that react with TBA), and form principally in meats and meat derivatives. Several organic or bio-organic acids, as shikimic and sorbic acids, react photometrically with TBA if a Malaprade reaction takes place before. A structural study of the red adduct TBA-MDA has been carried out.

Adipose tissue is an important source of adipose derived stem cells (ADSCs). These cells have the potential of being used for certain therapies, in which the main objective is to recover the function of a tissue/organ affected by a disease. In order to contribute to repair of the tissue, these cells should be able to survive and carry out their functions in unfavorable conditions after being transplanted. This process requires a better understanding of the biology involved: such as the time cells remain in the implant site, how long they stay there, and whether or not they differentiate into host tissue cells. This report focuses on these questions. ADSC were injected into three different tissues (substantia nigra, ventricle, liver) and they were tracked in vivo with a dual GFP-Luc reporter system. The results show that ADSCs were able to survive up to 4 months after the engraftment and some of them started showing resident cell tissue phenotype. These results demonstrate their long-term capacity of survival and differentiation when injected in vivo.

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The reaction of flavor aldehydes with 2-thiobarbituric acid (TBA) and the factors affecting this reaction have been studied. The formation rate of the 530−532 nm absorption band for detecting food rancidity through the TBA assay was dependent on the type of aldehyde and the reaction conditions. TBA reacted slowly with alkanals, and the yellow pigment (450 nm) was formed. Only after 1 h of heating at 100 °C was the red pigment formed. With 2-alkenals the reaction rate was more favorable for the red adduct (530−532 nm) formation, especially in excess TBA reagent and by employing an adequate heating time at 100 °C (water bath). For 2,4-dienals the orange pigment (494 nm) formation prevailed; the formation of the red adduct underwent a slow development (5 h at least). The development of the red adduct was favorable in an acetic acid concentration of 15−25% v/v. The yellow pigment was the only one that developed (although slowly) in glacial acetic acid medium. Keywords: Aldehydes; flavor; rancidity; 2-thiobarbituric acid (TBA)−aldehyde pigments; 2-thiobarbituric acid (TBA) assay

Aldehydes have been found in fruits and essential oils. But their presence in the off-flavor compounds (rancidity of foods) is well known. Aldehydes are characteristic compounds of secondary oxidation in the autoxidative process of fats, oils, lipidic foods and biological membranes. Malonaldehyde and other aldehydes responsible for rancidity can be evaluated through the thiobarbituric acid (TBA) assay. Alkanals, alkenals and dienals give characteristic pigments (yellow, orange, red pigments) with TBA reagent, which could be spectrophotometrically evaluated.Aldehydes have been detected in fruits, spices, essential oils, and as the components responsible for offflavors of edible fats and oils'. Malonaldehyde (MDA) seems that is not the exclusive responsible for the offflavors during the oxidation process. Other aldehydes have been recognized in oxidized fats, which are formed in the ultimate steps of the autoxidation mechanism, as a consequence of oxidative fissions. Statistical considerations have shown that total carbonyl compounds contribute with an appreciable correlation to the oxidative rancidity'. When 2-thiobarbituric acid (TBA) reacts with these aldehydes, alkylidene-, arylidene-2-thiobarbituric acids are formed. These coloured pigments (yellow, orange, red) show characteristic absorptions in the visible spectral A fruit can contain until two hundred distinct volatile compounds, among them aldehydes and ketones are relevant. Until twenty six carbonyl derivatives have been detected in the apple. Benzaldehyde is the characteristic impact substance in the flavor profile of the almonds and cherries. Anisaldehyde and salicylaldehyde appear in the vanilla and anise extracts4"*. Cinnamon contains cinnamaldehyde, and peas contain acetaldehyde traces. Cis-3hexenal and 2,4-pentadienal are involved in the soybean oil flavor. Hexanal and 2-hexenal cause the "unripe odors" in some fruits and vegetables. During the ripening process, cellular membranes are broken, and their fatty acids are oxidized, catalyzed by lipoxigenases. Then aldehydes are originated under enzymatic influence. The accumulation of these aldehydes can give rise to unpleasant odors, and even can originate toxicity problem^'^.Another well-known source of aldehydes can be the aminoacids, because enzymatic transamination, and subsequent decarboxylation, often occur during the ripening of fruits and vegetables. Also, pyridinic and pyrimidinic derivatives, provided that they do not possess 4-, 5-, or 6-substituents in their heterocyclic ring, can undergo the ring ~leavage'~, and so they originate MDA, which reacts quickly with TBA"-I7. Milk, beer and fruit juice develop oxidized flavors, hence n-hexanal, trans-2-hexenal, trans-2-heptenal are formed. During the storage of foods (dehydrated pota-Fat Sci. Technol. 97. Jahrgang Nr. 718 1995 Aldehyde in Lebensmitteln und ihre Beziehung zum TBS-Test fur die Bestimmung der RanziditatAldehyde entstehen beim sekundaren AutoxidationsprozeD von 81en. Fetten, lipidischen Lebensmitteln sowie biologischen Membranen und ...