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 alizari n, an anthraquinone, caffeine, a methyl xanthine derivative and quercetin, a flavonol were studied for their effect on elimination of metabolites of [14C]_N_ nitrosodiethylamine e 4 C-NDEA) through respiration in mice. Treatment with caffeine, quercetin and alizarin at doses of 200, 9 and 9 JLg/ml respectively, in drinking water enhanced the exhalation of 14C02, one of the major end products of NDEA metabolism. Radioactive CO2 exhaled in 60 min increaser! 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 14C02 peak was similar in ip and orally administered [ 14 C-NDEAJ. Increased detoxification/elimination of the carcinogen could be one of the mechanisms for the anticarcinogenic properties of these phytochemicals in lung tumori­ genesis induced by orally administered NDEA. Marked international variations in the number of deaths from cancer may be attributed to different en­ vironmental factors, life style and nutritional habits. Therefore, nutritional oncologists these days are try­ ing to identify the naturally occurring dietary factors, which are/or may be anticarcinogens. The identifica­ tion and characterization of these anti carcinogens in the diet may lead to new strategies for reducing the risk of human cancer. Any compound that can block the metabolic activation step, scavenge the reactive intermediates or enhance detoxification would be a potential chemopreventive agentl-4. Human diet con­ tains a complex mixture of phenols and estimated in­ dividual dietary consumption is as much as Ig of plant phenols per dayS. Many of these plant phenolics have been reported to exhibit chemopreventive prop­ erties against neoplasm. The two main classes of plant phenols are the plant pigments, flavonol and an­ thraquinone. These phenolics, which are widely dis­ tributed in plant kingdom, seem to be cancer­ preventive substances because of their strong antioxi­ dative activity and free radical scavenging potencl- 8 . All flavonoids may not be necessarily equally protec­ tive against all cancers or other chronic diseases and may also not be equally effective in modifying the mechanistic factors. Three dietary compounds, i.e.