Rosaria De Marco

Quantitative determination of fatty acid chain composition in pork meat products by high resolution 1H NMR spectroscopy

High resolution (1)H NMR spectroscopy was proposed for the determination of the fatty acid chain profile of lipids in pork meat products during ripening. Two typical Mediterranean PDO salami produced in Calabria, a region in the Southern Italy, were chosen as a case of study. Quantitative NMR analysis provided the fatty acid chain profiles of total lipid extracts. The transesterification of total lipid extracts furnished FAME mixtures that enabled quantitation of fatty acid acyl chains in the acylglycerol and FFA portions. In all cases, oleyl chains were predominant, and high amounts of polyunsaturated fatty acid chains were observed. The proposed spectroscopic method allowed also the estimation of the most important nutritional parameters of dry fermented meat products.

Simultaneous extraction and derivatization of amino acids and free fatty acids in meat products

In meat products the contents of free amino acids and free fatty acids are two important parameters used to establish their quality. These compounds play a very important role in defining the sensorial characteristics and acceptability of meat products. An innovative procedure for the measurement of free amino acid and fatty acid contents in meat and meat derivatives was developed. A single experiment can be performed in order to determine simultaneously the free amino acid and free fatty acid profiles. The analytes of interest are rapidly extracted from the meat matrix and derivatized by using methyl chloroformate. This reagent allows the transformation of the two groups of analytes into the corresponding N-methyloxycarbonyl amino acid methyl esters and fatty acid methyl esters that can easily be extracted and sampled for their further identification and quantitation. The measurement of the obtained amino acid and fatty acid derivatives is performed by GC/MS analysis and their concentrations are calculated by using two appropriate internal standards. The main advantage of the proposed protocol is the determination at the same time of two important classes of analytes that are of great importance in food analysis and characterization. Moreover, minimal sample manipulation and preparation, and reduced total extraction times are required to obtain the response with respect to conventional procedures, in which instead the analysis of both the two classes of compounds must be performed separately. The helpfulness of the protocol was tested in the analysis of a cured meat product that is typical of the South of Italy. The optimized protocol successfully allowed the determination of thirteen free amino acids and six free fatty acids, namely those most abundant in the lipid content of the cured meat product under evaluation.

A new non-natural arginine-like amino acid derivative with a sulfamoyl group in the side-chain

Sulfamoylation of the l-ornithine methyl ester side-chain generates a non-natural arginine isostere which can be coupled with N-Fmoc-l-proline to synthesize analogues which maintain the structural characteristics of the biologically important Pro-Arg dipeptide sequence. As a probe of its biological importance, the sulfamoylated amino acid derivative was also incorporated as P1 residue in tripeptide structures matching the C-terminal subsequence of fibrinogen. The reported results demonstrate that the functionalization of l-ornithine side-chain with a neutral sulfamoyl group can generate an arginine bioisostere which can be used for the synthesis of prototypes of a new class of human thrombin inhibitors.

Therapeutic potential of leptin receptor modulators

Leptin, a pleiotropic molecule mainly produced by adipose tissue, was first discovered as a hormone controlling body weight and energy expenditure. In addition, leptin can modulate several processes in peripheral tissues such as immune response, fertility, hematopoiesis and carcinogenesis. The development of molecules that block or stimulate leptin receptor may therefore serve as a potent tool for studying the role of leptin in mammalian physiology and pathology, but it also may open new possibilities for therapy. This article presents an overview of current knowledge on leptin receptor modulators focusing on leptin mutein, leptin peptide modulators as well as small molecules with heterocyclic structure.

An Efficient Preparation of N-Methyl-α-amino Acids from N-Nosyl-α-amino Acid Phenacyl Esters

In this paper we describe a simple and efficient solution-phase synthesis of N-methyl-N-nosyl-alpha-amino acids and N-Fmoc-N-methyl-alpha-amino acids. This represents a very important application in peptide synthesis to obtain N-methylated peptides in both solution and solid phase. The developed methodology involves the use of N-nosyl-alpha-amino acids with the carboxyl function protected as a phenacyl ester and the methylating reagent diazomethane. An important aspect of this synthetic strategy is the possibility to selectively deprotect the carboxyl function or alternatively both amino and carboxyl moieties by using the same reagent with a different molar excess and under mild conditions. Furthermore, the adopted procedure keeps unchanged the acid-sensitive side chain protecting groups used in Fmoc-based synthetic strategies.

Transformations of 3-hydroxy steroids with lewis and anhydrous protic acids: the case of pregn-4-en-3β,17α,20β-triol.

The acid‐catalyzed dehydration is one of the most important processes, which transforms 3‐hydroxy steroids into their corresponding unsaturated derivatives. This reaction is of great importance because it can produce molecules that play a key role in the understanding of the natural metabolism of steroids. Sterol dehydration is generally performed with aqueous acidic systems, and the treatment often affords low yields of the desired compounds and/or complex mixtures of by‐products. In this paper, we report the results obtained from the study of the structural and stereochemical effects of the acid‐induced reaction of pregn‐4‐en‐3β,17α,20β‐triol in anhydrous systems. In particular, the treatment of this trihydroxy steroid model with Lewis acids leads to the corresponding Δ3,5‐steradiene as the only product and in very high yields. With Lewis acids, no modifications of the 1,2‐diol function on the D‐ring are observed, even when the reactions are performed at high temperatures. Protic acid catalysis in non‐aqueous organic solvents causes the formation of an epimeric mixture of the corresponding Δ3,5‐steradiene derivatives by a partial stereochemical inversion of the asymmetric C‐17. The reactivity of the 17α,20β‐diolic residue is also evaluated by exposing pregn‐4‐en‐3β,17α,20β‐triol and the corresponding Δ3,5‐steradiene to the prolonged action of anhydrous protic acid systems under thermal conditions.

Site-selective methylation of N(beta)-nosyl hydrazides of N-nosyl protected alpha-amino acids.

The methylation reaction of N(beta)-nosyl hydrazides of N-nosyl protected alpha-amino acids by using diazomethane shows a controlled regiochemical trend and makes it possible to obtain the corresponding products methylated at specific positions depending on the amount of diazomethane used. The observed selectivity is closely connected with the different acidity of sulfonyl hydrazide, sulfonamide, and acyl hydrazine protons present in the analyzed substrates. The reactivity order of these three diverse reactive sites is supported by theoretical calculations. The hydrazine derivatives considered in this work belong to a class of compounds with interesting biological activity and of great interest in organic synthesis.