Safety assessment of N-acetyl-L-threonine.

N-acetyl-L-threonine (NAT) is a dietary constituent that has been identified at low concentrations (< 1 microg/g fresh weight) in numerous foods. The current paper reports the outcome of toxicology studies conducted to assess the effects of NAT. No evidence of mutagenicity or genotoxicity was observed in in vitro bacterial or in vivo mammalian studies. No mortalities or evidence of adverse effects were observed in Sprague-Dawley (SD) rats following acute oral administration of 2000 mg of NAT/kg of body weight (kg of bw). A 28-day repeated dose toxicity study was conducted in SD rats by incorporating NAT into diets at concentrations targeting up to 1000 mg of NAT/kg of bw/day. All rats survived until scheduled sacrifice and no biologically significant differences were observed in any of the NAT treatment groups for body weights, feed consumption, clinical signs, behavioral, ophthalmology, hematology, coagulation, clinical chemistry, organ weights, or gross or microscopic changes. Based on these results, NAT does not represent a risk for mutagenicity or genotoxicity, is not acutely toxic, and the no-observed-adverse-effect-level (NOAEL) for systemic toxicity from repeated dose dietary exposure to NAT is 848.5 and 913.6 mg/kg of bw/day for male and female SD rats, respectively.

Toxicology studies with N-acetyl-L-serine.

N-Acetyl-L-serine (NAS) is a component of dietary proteins and a minor constituent of foods as a free amino acid. The current paper reports the outcome of toxicology studies conducted to assess the safety of NAS. No evidence of mutagenicity was observed in the reverse bacterial mutation assay. Genotoxicity was not observed in the bone marrow micronucleus assay conducted in mice. No mortalities or evidence of adverse effects were observed in Sprague-Dawley (SD) rats following acute oral administration at a dose of 2000 mg of NAS/kg of body weight. Similarly, no evidence of adverse effects was observed in SD rats following repeated dose dietary exposure (28-days) to targeted doses of 100, 500, or 1000 mg of NAS/kg of body weight/day. All rats survived until scheduled sacrifice and no biologically significant differences were observed in any of the response variables from the NAS exposure groups compared with untreated control groups. Based on these results, NAS does not represent a risk for mutagenicity or genotoxicity, is not acutely toxic, and the no-observed-adverse-effect-level (NOAEL) for systemic toxicity from repeated dose dietary exposure to NAS is 839.7 and 893.6 mg of NAS/kg of body weight/day for male and female rats, respectively.