Urinary Methyleugenol-deoxyadenosine Adduct as a Potential Biomarker of Methyleugenol Exposure in Rats

Methyleugenol (ME), a natural ingredient of several herbs and spices used in the human diet, is hepatocarcinogenic in rodents. Following metabolic activation to the reactive carbocation intermediate, ME can bind covalently to DNA, which is directly associated with its carcinogenicity. In this work, a non-invasive approach to determine ME exposure was established by monitoring the urinary N6-(methylisoeugenol-3'-yl)-2'-deoxyadenosine (ME-dA) adduct. The developed method entails liquid-liquid extraction enrichment of urinary ME-dA, incorporation of deuterated ME-dA as an internal standard, and analysis by liquid chromatography coupled tandem mass spectrometry. Male rats (10-12 weeks, 180-200 g) were treated (p.o.) with ME, and ME-dA was excreted in urine in a dose- and time-dependent manner. The non-invasive approach enabled us to successfully determine exposure to ME-containing herbs and spices. These results suggest that ME-dA can potentially serve as an effective biomarker of ME exposure in rats. It is expected that the developed approach of detecting urinary ME-dA will facilitate the investigation of ME carcinogenesis.