Safety assessment of (S)-Equol: Subchronic toxicity study in Sprague Dawley Rats

(S)-Equol is a chemically synthesized nutraceutical compound and its consumption provides several health benefits for humans. The new nutraceutical, enantiopure (S)-Equol was studied for acute and sub-chronic toxicity in Sprague Dawley Rats. The oral acute toxicity study showed that (S)-Equol is safe > 2000-5000 mg/kg body weight and it classified into GHS category 5/Unclassified. The repeated dose administration of (S)-Equol at dose levels of 20, 60, and 160 mg/kg body weight for 14 days and 250, 500, and 1000 mg/kg body weight for 90-consecitve days. The 14 days repeated-dose toxicity study showed no adverse effects in Sprague Dawley rats. The 90-day repeated dose toxicity study showed a reduction in body weight gain than that of control group. No treatment-related contrary effects were perceived on haematology, clinical chemistry, coagulation, urine parameters analysed, organ weights (absolute and relative), neurological and ophthalmological examination. No treatment-related abnormal gross pathological findings were obtained from gross necropsy. However, as a treatment-related effect, a significant decrease in cholesterol levels for 14 and 90 days of repeated dose administration was observed, which is considered as a pharmacological class effect of the (S)-Equol. In comparison to the corresponding vehicle control group, the high dose treatment group for both sexes showed no treatment-related histopathological abnormalities. For female rats, the no-observed-adverse-effect-level (NOAEL) was 250 mg/kg/day and for male rats, the lowest-observed-adverse-effect level (LOAEL) was 250 mg/kg/day.