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Related Concept Videos

2° Amines to N-Nitrosamines: Reaction with NaNO201:20

2° Amines to N-Nitrosamines: Reaction with NaNO2

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Secondary amines react with nitrous acid to form N-nitrosamines, as depicted in Figure 1. Nitrous acid, a weak and unstable acid, is formed in situ from an aqueous solution of sodium nitrite and strong acids, such as hydrochloric acid or sulfuric acid, in cold conditions. In the presence of an acid, the nitrous acid gets protonated. The subsequent loss of water results in the formation of the electrophile known as nitrosonium ion.
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Physical Properties of Amines01:26

Physical Properties of Amines

3.2K
Amines with low molecular weight are usually gaseous at room temperature, while those with high molecular weight are liquid or solids in nature. Usually, low molecular weight amines have a rotten fish-like smell. Diamines typically have a pungent smell. For instance, cadaverine and putrescine, depicted in Figure 1, are two molecules responsible for decaying tissue.
3.2K
Amines: Introduction01:07

Amines: Introduction

4.5K
Amines are organic derivatives of ammonia. They are formed by replacing one or more ammonia protons with alkyl or aryl groups. Depending upon the number of organyl groups bonded to nitrogen, amines are classified as primary, secondary, or tertiary. Primary amines have one organyl group attached to the nitrogen atom, while secondary and tertiary amines have two and three organyl groups attached to the nitrogen atom, respectively.
4.5K
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview01:26

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview

3.3K
Nitrous acid and nitric acids are two types of acids containing nitrogen, among which nitrous acid is weaker than nitric acid. Nitrous acid with a pKa value of 3.37 ionizes in water to give a nitrite ion and the hydronium ion.
The nitrous acid is unstable. Hence, it is formed in situ from a solution of sodium nitrite and cold aqueous acids such as hydrochloric or sulfuric acid. In an acidic solution, the –OH group of nitrous acid undergoes protonation to give oxonium ion, followed by...
3.3K
Preparation of Amines: Alkylation of Ammonia and Amines01:30

Preparation of Amines: Alkylation of Ammonia and Amines

3.4K
Alkylation is one of the methods used to prepare amines. Direct alkylation of ammonia or a primary amine with an alkyl halide gives polyalkylated amines along with a quaternary ammonium salt through successive SN2 reactions. This process of making the quaternary salt through the direct alkylation method is called exhaustive alkylation.
Each alkylation step makes the nitrogen center more nucleophilic, which triggers successive alkylations until a quaternary ammonium salt is formed. Considering...
3.4K
Mass Spectrometry of Amines01:19

Mass Spectrometry of Amines

4.3K
In mass spectroscopy, amines undergo fragmentation to give parent ions with odd molecule weights. This observed mass spectrum follows the nitrogen rule: a molecule with an odd number of nitrogen atoms produces a parent ion with an odd molecular weight. The remaining fragments have an even mass.
Amines undergo fragmentation through α cleavage, producing nitrogen-containing cations—iminium ions—and alkyl radicals. Mass spectra of aromatic and cyclic aliphatic amines exhibit...
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A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s
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A deep dive into historical Ames study data for N-nitrosamine compounds.

Rachael E Tennant1, David J Ponting1, Andrew Thresher1

  • 1Lhasa Limited, Granary Wharf House, 2 Canal Wharf, Leeds, West Yorkshire, LS11 5PS, UK.

Regulatory Toxicology and Pharmacology : RTP
|July 26, 2023
PubMed
Summary

The Ames test may need optimized conditions to accurately detect mutagenic risks from N-nitrosamines, which are potent carcinogens. This study explores variations in the bacterial reverse mutation assay to improve carcinogenicity prediction for these drug impurities.

Keywords:
AmesCarcinogenicityImpuritiesMutagenicityNitrosaminesOECD 471Pharmaceuticals

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Area of Science:

  • Drug Safety Assessment
  • Toxicology
  • Genotoxicity Testing

Background:

  • Mutagenicity data, particularly from the OECD-471 bacterial reverse mutation (Ames) assay, is crucial for regulatory drug approval.
  • N-Nitrosamines are potent mutagenic carcinogens, and their presence as pharmaceutical impurities raises safety concerns.
  • Concerns exist that the standard Ames test may lack sensitivity to detect N-nitrosamine mutagenicity, potentially underestimating carcinogenicity risk.

Purpose of the Study:

  • To investigate whether variations in the Ames test protocol can improve its ability to predict N-nitrosamine carcinogenicity.
  • To analyze the impact of different testing parameters on the Ames test's predictive performance for N-nitrosamines.
  • To enhance the accuracy and reliability of the Ames test for identifying potential carcinogens within the N-nitrosamine class.

Main Methods:

  • Collation of public N-nitrosamine data, including Ames test results and rodent carcinogenicity bioassays.
  • Analysis of how modifications to the OECD 471-compliant Ames test affect predictive outcomes.
  • Evaluation of parameters such as bacterial strain, metabolic activation systems, solvent choice, and incubation methods.

Main Results:

  • Variations in Ames test conditions, including strain selection and metabolic activation, can influence the detection of N-nitrosamine mutagenicity.
  • Specific modifications may enhance the assay's sensitivity to N-nitrosamines, improving correlation with carcinogenicity data.
  • The study identifies key parameters that impact the predictive power of the Ames test for this class of compounds.

Conclusions:

  • Optimizing the Ames test protocol is essential for accurately assessing the mutagenic potential of N-nitrosamines.
  • Improved Ames test methodologies can increase confidence in predicting carcinogenicity risk from N-nitrosamine impurities.
  • This research provides insights for refining genotoxicity testing strategies for pharmaceutical safety evaluations.