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Photoinitiators are widely used to cure ink on packaging materials used in food applications such as carton boards and can contaminate the food by migrating into the food. In this contribution, a fast and reliable confirmation method for the determination of photoinitiators in dry foodstuffs is described: benzophenone (BP), 4,4'-bis(diethylamino) benzophenone (DEAB), 2-chloro-9H-thioxanthen-9-one (CTX), 1-chloro-4-ropoxy-9H-thioxanthen-9-one (CPTX), 2,2-dimethoxy-2-phenyl acetophenone (DMPA), 4-(dimethylamino) benzophenone (DMBP), 2-ethylanthraquinone (EA), 2-ethylhexyl-4-dimethylaminobenzoate (EDB), ethyl-4-dimethylaminobenzoate (EDMAB), 4-hydroxybenzophenone (4-HBP), 1-hydroxycyclohexyl phenyl ketone (HCPK), 2-hydroxy-4-methoxybenzophenone (HMBP), 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (HMMP), 2-isopropyl-9H-thioxanthen-9-one (ITX), 4-methylbenzophenone (MBP), 4,4'-bis(dimethylamino) benzophenone (MK) and 4-phenylbenzophenone (PBZ). Dry foodstuffs were extracted using acetonitrile, followed by the addition of inorganic salts to precipitate fatty residues. After filtration, the extract was analysed using ultra-performance liquid chromatography in combination with tandem mass spectrometry (UPLC-MS/MS). Quantification was carried out using benzophenone-d10 (BP-d10) as internal standard. The presented method was successfully validated in-house. Afterwards, the procedure was applied in a marketing study, investigating 97 dry foodstuffs purchased on the Belgian market. In 89% of the samples, at least one photoinitiator was detected. The photoinitiators BP, EDMA and DMPA were most frequently found, while some photoinitiators (CPTX, DEAB, DMBP, HCPK, HMBP and MK) were never detected. Copyright (C) 2016 John Wiley & Sons, Ltd.

The purified multienzyme complex, fatty acid synthetase of yeast, produces palmityl-CoA and stearyl-CoA in equal amounts under standard conditions, with adequate NADPH, and a 1:2 ratio of acetyl-CoA and malonyl-CoA. Based on the known enzymatic properties of fatty acid synthetase a model which rationalizes the chain termination at the level of C16 and C18-acid is proposed. The model is based on two assumptions that are supported by experimental evidence: (a) the probability of any covalently enzyme-bound saturated acyl residue forming a product by transfer to CoA is determined by the relative velocities of the condensing and transferring reactions. (b) The growing alkan chain interacts with the enzyme protein only after a chain length of 13 carbon atoms has been attained; this interaction changes the relative velocities in favour of product formation by an energy increment of -0.9 kcal for each additional methylene group beyond the 13th. 3 To calculate the probability of product release at a particular chain length, an equation was derived from the model describing quantitatively the observed product distribution. 4 The formula suggests conditions under which either short acyl-CoA derivatives or exclusively stearyl-CoA can be produced. Synthesis under these conditions was examined experimentally and results indicated that the formula can be applied to a wide range of experimental conditions. 5 Because the condensation reaction in fatty acid synthesis is the rate limiting step under normal conditions, saturated acyl residues have the longest life-time as intermediates and consequently the highest probability of leaving the enzyme complex as an endproduct. The reduction reactions can be made rate limiting when the NADPH level drops. Under such circumstances β-ketoacyl-CoA's and α,β-unsaturated acyl-CoA's appear as endproducts. With NADH as electron donor the first reduction is slowed to such an extent that predominantly β-ketoacyl-CoA's derivatives are synthesized. 6 The possibility that the enzyme complex catalyses synthesis of short chain fatty acids and and β-ketoacids in vivo is discussed.

The intermediates in the biological breakdown and synthesis of fatty acids are S-acyl derivatives of coenzyme A. Fatty acid synthesis is accomplished through repetition of a cycle of four consecutive reactions: a. Condensation of two molecules of acetyl CoA to form acetoacetyl CoA and coenzyme A (CoASH); b. reduction of acetoacetyl CoA to β-hydroxybutyryl CoA; c. dehydration of β-hydroxybutyryl CoA to crotonyl CoA, and d. reduction of crotonyl CoA to butyryl CoA. A new cycle is started by the reaction of butyryl CoA with another molecule of acetyl CoA to form β-keto-caproyl CoA + CoA-SH, and so forth. The cycle is repeated eight times until stearyl CoA is formed. All four reactions of the fatty acid cycle are reversible and fatty acid oxidation, once the fatty acid is activated through conversion to the corresponding S-acyl CoA derivative, proceeds by a reversal of the above sequence. There are two main mechanisms for activation of fatty acids: (a) By a reaction with ATP and CoA to form S-acyl CoA, adenosine monophosphate and pyrophosphate, and (b) by transfer of CoA from certain acyl CoA compounds such as acetyl CoA or succinyl CoA. The isolation and identification of some of the key enzymes of fatty acid metabolism is outlined and their mechanism of action discussed.

A comprehensive two-dimensional liquid chromatography-based biomimetic platform (LCxLC) has been developed and validated for drug diffusion studies. Human serum albumin (HSA) and immobilized artificial membrane (IAM) were thereby used in the first (1D) and second (2D) separation dimension, respectively. While the former was meant to emulate the blood, the latter was instead intended to mimic the intestinal mucosa epithelium. Therefore, the experimental conditions, i.e. pH, temperature and buffer composition, were modulated to reflect faithfully in vivo conditions. 30 compounds, whose effective intestinal permeability (Peff) assayed in situ on humans by a validated technique was known from the literature, were used as model drugs. A good and orthogonal separation was achieved for the whole dataset, although for a better distribution of the most polar compounds in the elution window a segmented gradient elution program had to be employed. Interestingly, the passively uptaken compounds having the most favourable Peff populated a specific area of the 2D plots, implying that the affinity for HSA and IAM has to lie in specific ranges in order for a compound to be satisfactorily absorbed from the intestinal lumen. Although these results should be regarded as preliminary, this work paves an entirely new and unprecedented way to profile pharmaceutically relevant compounds for their in vivo absorption and distribution potential.

The Blood-Brain Barrier (BBB) plays an essential role in protecting the brain tissues against possible injurious substances. In the present work, 79 neutral, basic, acidic and amphoteric structurally unrelated analytes were considered and their chromatographic retention coefficients on immobilized artificial membrane (IAM) stationary phase were determined employing a mass spectrometry (MS)-compatible buffer based on ammonium acetate. Their BBB passage predictive strength was evaluated and the statistical models based on IAM indexes and in silico physico-chemical descriptors showed solid statistics ( r 2 ( n − 1) = 0.78). The predictive strength of the indexes achieved by the MS-compatible method was comparable to that achieved by employing the more “biomimetic” Dulbecco’s phosphate buffered saline, even if some differences in the elution order were observed. The method was transferred to the MS, employing a diode-array-detection coupled to an electrospray ionization source and a time-of-flight analyzer. This setup allowed the simultaneous analysis of up to eight analytes, yielding a remarkable acceleration of the analysis time.