RECENT SYNTHETIC APPLICATIONS OF N-NITROSAMINES AND RELATED COMPOUNDS

Food contaminants: Impact of food processing, challenges and mitigation strategies for food security

Food preparation involves the blending of various food ingredients to make more convenient processed food products. It is a long chain process, where each stage posing a risk of accumulating hazardous contaminants in these food systems. Protecting the public health from contaminated foods has become a demanding task in ensuring food safety. This review focused on the causes, types, and health risks of contaminants or hazardous chemicals during food processing. The impact of cooking such as frying, grilling, roasting, and baking, which may lead to the formation of hazardous by-products, including polycyclic aromatic hydrocarbons (PAHs), heterocyclic amines (HCAs), acrylamide, advanced glycation end products (AGEs), furan, acrolein, nitrosamines, 5-hydroxymethylfurfural (HMF) and trans-fatty acids (TFAs). Potential health risks such as carcinogenicity, genotoxicity, neurotoxicity, and cardiovascular effects are emerging as a major problem in the modern lifestyle era due to the increased uptakes of contaminants. Effects of curing, smoking, and fermentation of the meat products led to affect the sensory and nutritional characteristics of meat products. Selecting appropriate cooking methods include temperature, time and the consumption of the food are major key factors that should be considered to avoid the excess level intake of hazardous contaminants. Overall, this study underscores the importance of understanding the risks associated with food preparation methods, strategies for minimizing the formation of harmful compounds during food processing and highlights the need for healthy dietary choices to mitigate potential health hazards.

Regulatory Experiences with Root Causes and Risk Factors for Nitrosamine Impurities in Pharmaceuticals

N-Nitrosamines (also referred to as nitrosamines) are a class of substances, many of which are highly potent mutagenic agents which have been classified as probable human carcinogens. Nitrosamine impurities have been a concern within the pharmaceutical industry and by regulatory authorities worldwide since June 2018, when regulators were informed of the presence of N-nitrosodimethylamine (NDMA) in the angiotensin-II receptor blocker (ARB) medicine, valsartan.  Since that time, regulatory authorities have collaborated to share information and knowledge on issues related to nitrosamines with a goal of promoting convergence on technical issues and reducing and mitigating patient exposure to harmful nitrosamine impurities in human drug products. This paper shares current scientific information from a quality perspective on risk factors and potential root causes for nitrosamine impurities, as well as recommendations for risk mitigation and control strategies.

An Organic Chemist's Guide to N-Nitrosamines: Their Structure, Reactivity, and Role as Contaminants

N-Nitrosamines are a class of compounds notorious both for the potent carcinogenicity of many of its members and for their widespread occurrence throughout the human environment, from air and water to our diets and drugs. Considerable effort has been dedicated to understanding N-nitrosamines as contaminants, and methods for their prevention, remediation, and detection are ongoing challenges. Understanding the chemistry of N-nitrosamines will be key to addressing these challenges. To facilitate such understanding, we focus in this Perspective on the structure, reactivity, and synthetic applications of N-nitrosamines with an emphasis on alkyl N-nitrosamines. The role of N-nitrosamines as water contaminants and the methods for their detection are also discussed.

A combined experimental and DFT mechanistic study for the unexpected nitrosolysis of N-hydroxymethyldialkylamines in fuming nitric acid

The reaction of dimorpholinomethane in fuming HNO3 was investigated. Interestingly, the major product was identified as N-nitrosomorpholine and a key intermediate N-hydroxymethylmorpholine was detected during the reaction by 1H-NMR tracking which indicates that the reaction proceeds via an unexpected nitrosolysis process. A plausible nitrosolysis mechanism for N-hydroxymethyldialkylamine in fuming nitric acid involving a HNO3 redox reaction is proposed, which is supported by both experimental results and density functional theory (DFT) calculations. The effects of ammonium nitrate and water on the nitrosolysis were studied using different ammonium salts as additives and varying water content, respectively. Observations show the key role of ammonium ions and a small amount of water in promoting the nitrosolysis reaction. Furthermore, DFT calculations reveal an essential point that ammonia, merged from the decomposition of the ammonium salts, acts as a Lewis base catalyst, and the hydroxymethyl group of the substrate participates in a hydrogen-bonding interaction with the NH3 and H2O molecules.

Qualitative thin-layer and high-performance liquid chromatographic analysis of 1-substituted diazen-1-ium-1,2-diolates on aminopropyl-bonded silica gel

High-performance liquid (HPLC) and thin-layer (TLC) chromatographic methods for the detection and quantification of diazeniumdiolates are described. The HPLC determinations were made using a Rocket Platinum NH2 column (7 x 53 mm, 100-A pore size, 3-microm particle size), under isocratic conditions with mixtures of acetonitrile, methanol, and water containing 0.1% diethylamine (v/v), at a flow rate of 2.5 ml/min, a column temperature of 22 degrees C, and UV detection at 250 nm. The TLC determinations were similarly made using Merck NH2 F254S precoated glass plates (approximately 2 x 5 cm, 5-microm particle size, 0.2-mm layer thickness) with mixtures of acetonitrile, methanol, and water containing 0.1% diethylamine (v/v). Preexisting traces of carcinogenic nitrosamines were detected in some samples of diazeniumdiolates. The methods provide a more efficient means of characterizing the purity of diazeniumdiolate samples prepared for use in biomedical applications than older procedures which rely on differential absorbance measurements at 250 and 350 nm, respectively.

Synthesis, Characterization, and Molecular Structures of Diethylnitrosamine Metalloporphyrin Complexes of Iron, Ruthenium, and Osmium

Diethylnitrosamine reacts with [(TPP)Fe(THF)(2)]ClO(4) (TPP = 5,10,15,20-tetraphenylporphyrinato dianion) in toluene to generate the bis-nitrosamine complex, [(TPP)Fe(Et(2)NNO)(2)]ClO(4), in 96% isolated yield. The related [(TTP)Fe(Et(2)NNO)(2)]SbF(6) (TTP = 5,10,15,20-tetra-p-tolylporphyrinato dianion) complex is prepared in 70% isolated yield via a similar reaction in CH(2)Cl(2). Reaction of [(TPP)Fe(Et(2)NNO)(2)]ClO(4) in CH(2)Cl(2) with NO gas results in the displacement of one of the Et(2)NNO ligands to give the air-sensitive and thermally sensitive [(TPP)Fe(NO)(Et(2)NNO)]ClO(4) derivative. Reaction of (OEP)Ru(CO) (OEP = 2,3,7,8,12,13,17,18-octaethylporphyrinato dianion) with NOBF(4) in CH(2)Cl(2) gives [(OEP)Ru(NO)(H(2)O)]BF(4) as the final isolated product (after exposure to air) in 71% isolated yield. The aqua ligand is then displaced by Et(2)NNO in CH(2)Cl(2) to give [(OEP)Ru(NO)(Et(2)NNO)]BF(4) in 82% isolated yield. The valence isoelectronic (OEP)Ru(CO)(Et(2)NNO) compound is prepared in 71% isolated yield by the addition of excess Et(2)NNO to (OEP)Ru(CO) in CH(2)Cl(2). The nitrosyl amine complex [(OEP)Ru(NO)(HNEt(2))]BF(4) is prepared (i) in 78% yield by diethylamine addition to [(OEP)Ru(NO)(H(2)O)]BF(4) or (ii) in 71% isolated yield by diethylamine addition to [(OEP)Ru(NO)(Et(2)NNO)]BF(4). The osmium nitrosamine complexes, (TTP)Os(CO)(Et(2)NNO) and (OEP)Os(CO)(Et(2)NNO), are prepared in 74% and 66% yields, respectively, by diethylnitrosamine addition to the precursor (porphyrin)Os(CO) compounds in CH(2)Cl(2). The nitrosyl [(OEP)Os(NO)(Et(2)NNO)]BF(4) derivative is prepared in quantitative yield (by IR and (1)H NMR spectroscopy) by the reaction of (OEP)Os(CO)(Et(2)NNO) with NOBF(4). Labeling studies using (15)NOBF(4), Et(2)N(15)NO, and Et(2)NN(18)O have been used to assign the nitrosyl and nitrosamine bands in the IR spectra of several of the complexes. The solid-state structures of [(TPP)Fe(THF)(2)]ClO(4), [(TPP)Fe(Et(2)NNO)(2)]ClO(4), [(OEP)Ru(NO)(H(2)O)]BF(4), (OEP)Ru(CO)(Et(2)NNO), and (TTP)Os(CO)(Et(2)NNO) have also been determined by single-crystal X-ray diffraction. The Et(2)NNO ligands display a rare eta(1)-O binding mode in all three nitrosamine complexes.

Microsomal metabolism of the Z and E isomers of N-nitroso-N-methyl-N-n-pentylamine

N-Nitrosomethyl-N-n-pentylamine was separated into its E and Z isomers by HPLC. When the metabolism was examined using microsomes isolated from uninduced Fischer 344 rats, it was found that, at a constant final concentration of 0.5 mM, the yield of formaldehyde produced increased as the proportion of the Z isomer rose. The yield of valeraldehyde, on the other hand, decreased with an increasing proportion of the Z isomer. Kinetic constants were determined for the metabolism of the two isomers. During the metabolism of the Z isomer, the Vmax was 2.2-fold higher for the formation of formaldehyde than that for the E. The Vmax for valeraldehyde was 2.0-fold lower during the metabolism of the Z isomer. The results indicate that the relative position of the nitroso group can have a profound effect on the metabolism of each side of this type of molecule.