An assessment of mutagenicity, genotoxicity, acute-, subacute and subchronic oral toxicity of paraxanthine (1,7-dimethylxanthine)

Paraxanthine or 1,7-dimethylxanthine is a natural dietary component and the main metabolite of caffeine in humans. A battery of toxicological studies was conducted in accordance with international guidelines to investigate mutagenicity, genotoxicity and acute and repeated-dose oral toxicity in rats of synthetic paraxanthine (ENFINITY™, Ingenious Ingredients, L.P., >99% purity). There was no evidence of mutagenicity in a bacterial reverse mutation as well as in an in vitro mammalian chromosomal aberration test. There was no evidence of genotoxicity in an in vivo mammalian erythrocyte micronucleus test as well as in an in vitro mammalian cell gene mutation test. An acute oral toxicity test resulted in a LD50 value of 1601 mg/kg bw/d. Paraxanthine did not cause mortality or toxic effects in a subacute 28-day repeated-dose oral toxicity study at daily doses of 75, 150, or 300 mg/kg bw/d (each group n = 10 per sex), administered by gavage. Paraxanthine also did not cause mortality or toxic effects in a subchronic 90-day repeated-dose oral toxicity study at daily doses of 75, 150, or 300 mg/kg bw/d (each group n = 10 per sex), administered by gavage. The no observed adverse effect level (NOAEL) determined from the 90-day study was greater than or equal to 300 mg/kg bw/d, the highest dose tested, for both male and female Wistar rats.