Progress towards the characterisation of faecal compounds.

Area of Science:

• Analytical Chemistry
• Gastroenterology
• Cancer Research

Background:

• Intestinal nitrosation generates Apparent Total N-nitroso Compounds (ATNCs), associated with increased colon cancer risk, particularly from red meat consumption.
• Modern Liquid Chromatography-Mass Spectrometry (LC-MS) enables direct detection of ATNC components in biological samples like fecal water.
• Identifying specific N-nitrosamines among numerous compounds in complex matrices is a significant analytical challenge.

Purpose of the Study:

• To develop a novel and practical method for identifying unknown N-nitrosamines in fecal and ileostomy samples.
• To leverage advanced LC-MS techniques combined with stable isotope labeling for enhanced N-nitrosamine detection.
• To investigate the in vivo formation and detection of N-nitroso compounds relevant to gastrointestinal health and disease.

Main Methods:

• Further nitrosation of fecal and ileostomy fluids to increase ATNC concentration.
• Derivatization of samples using both 14N and 15N labeled nitrite.
• Parallel analysis of chromatograms to detect mass differences indicative of N-nitrosamines.
• Integration of MS with traditional methods like Thermal Energy Analyzer (TEA) and UV irradiation degradation.

Main Results:

• A repeatable method for identifying unknown ATNCs in human biological samples was established.
• The approach successfully identified 30 putative N-nitroso compounds based on characteristic mass differences.
• The study demonstrated the utility of stable isotope labeling in N-nitrosamine discovery.

Conclusions:

• The developed method provides a novel and practicable means for identifying N-nitrosamines in complex biological matrices.
• This technique aids in understanding the role of N-nitroso compounds in gastrointestinal health and disease.
• The findings contribute to the analytical toolkit for investigating diet-related cancer risks.