Acute and 90-day subchronic toxicity studies of Silk peptide E5K6, in Sprague–Dawley rats

► We performed acute and 90-day subchronic oral toxicity studies of Silk peptide E5K6. ► Acute oral ALD of E5K6 was considered to be higher than 5000mg/kg in rats. ► Subchronic oral NOAEL of E5K6 was considered to be higher than 2000mg/kg in rats. ► The target organ was not identified in subchronic toxicity study. Acute and 90-day subchronic oral toxicity studies of Silk peptide E5K6 were performed in Sprague–Dawley rats. In the acute toxicity study, Silk peptide E5K6 was administered orally to male and female rats at a single dose of 2000 and 5000mg/kg. Mortality, clinical signs and body weight changes were monitored for 14days. There were no treatment-related changes in these parameters. Therefore, the Approximate Lethal Dose (ALD) of Silk peptide E5K6 in male and female rats is higher than 5000mg/kg. In the subchronic toxicity study, Silk peptide E5K6 was administered orally to male and female rats for 90days at a single dose of 500, 1000, and 2000mg/kg. There were no toxicologically significant changes in clinical signs, body weight, food and water consumptions, ophthalmoscopic examination, urinalysis, hematological and serum biochemical examinations, necropsy findings, organ weights and histopathological examination of all of the animals treated with Silk peptide E5K6. These results suggest that the oral No Observed Adverse-Effect Level (NOAEL) of Silk peptide E5K6 is greater than 2000mg/kg/day in both sexes and the target organs were not established.