Caffeine, quercetin and alizarin stimulate the exhalation of metabolic products of [¹⁴C]-N-nitrosodiethylamine in mice

Naturally occurring plant products belonging to different chemical classes namely alizarin, an anthraquinone, caffeine, a methylxanthine derivative and quercetin, a flavonol were studied for their effect on elimination of metabolites of [¹⁴C]-N-nitrosodiethylamine (¹⁴C-NDEA) through respiration in mice. Treatment with caffeine, quercetin and alizarin at doses of 200, 9 and 9 μg/ml respectively, in drinking water enhanced the exhalation of ¹⁴CO₂, one of the major end products of NDEA metabolism. Radioactive CO₂ exhaled in 60 min increased by 2, 1.61 and 1.4-folds in animals treated with caffeine, quercetin and alizarin for 8 weeks respectively. This increase in exhalation in caffeine-treated animals was achieved even in 2 weeks. These compounds had no adverse effects on the absorption of radioactive NDEA from the gut of the animals as shape and time of ¹⁴CO₂ peak was similar in ip and orally administered [¹⁴C-NDEA]. Increased detoxification/elimination of the carcinogen could be one of the mechanisms for the anticarcinogenic properties of these phytochemicals in lung tumorigenesis induced by orally administered NDEA.