Characterization of biotransformation, transmission and elimination processes in humans: Influence on the odorant and metabolite profiles of breath, urine and human milk

• Applicant: Professorin Dr. Andrea Büttner
• Subject Area: Food Chemistry ; Analytical Chemistry
• Term: from 2013 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 245860176

An increasing number of studies report biotransformation processes that may lead to substantial modification of odorants but also odorless volatile substances that are ingested with food. Also, neo-formation of odorants from non-odorous precursors due to physiological processes has been described in the literature. To characterize these processes, sensorially relevant substances of garlic, together with their potential metabolites, are monitored in human milk, but also in urine and exhaled breath of human subjects. In our previous project Bu 1351/15-1 we comprehensively investigated a food-relevant situation involving intervention with raw garlic, thereby comparing data from the intervention with the respective control experiments.The sensory evaluation of the human milk taken before and after the consumption of raw garlic showed that the odor of milk taken about 2.5 h after garlic consumption was altered, and that a garlic/cabbage-like odor was detectable. Using gas chromatography-mass spectrometry/olfactometry (GC-MS/O), three garlic-derived metabolites, namely allyl methyl sulfide (AMS), allyl methyl sulfoxide (AMSO) and allyl methyl sulfone (AMSO2), could be identified in breast milk and urine samples after raw garlic intake. However, AMS was the only odor active metabolite emitting a clear garlic-like smell; the two other metabolites were odorless even at high concentrations. The excretion rates of the three metabolites into the specific bodily fluids were found to be strongly time-dependent and differed between the individual test persons as well as for one individual at different test days. In parallel we applied proton transfer reaction-mass spectrometry (PTR-MS) coupled with a breath end tidal sampling system for the sampling of alveolar air of test persons in relation to garlic intake. The analysis revealed the appearance of AMS and methanethiol in the exhaled breath of test persons consuming garlic, but again with very different excretion rates for different individuals. These findings demonstrate that, on the one hand side, the volatile odorant fraction of raw garlic is strongly metabolized, but, on the other side, that there are similar excretion pathways for garlic-derived metabolites via different bodily fluids.Based on these premises, biotransformation and transmission, as well as elimination processes are now proposed to be monitored under real-life conditions for roasted and cooked garlic ingestion; thereby, garlic odorants and metabolites will again be monitored qualitatively and quantitatively, but also on a time-resolved basis. This approach will enable us to elucidate the underlying temporal kinetics, again comparing the physiological media breast milk, urine and breath, and to translate the knowledge gained with fresh garlic into effects that are related to processed garlic.

• DFG Programme: Research Grants