Evidence of non-carcinogenicity of rhubarb extract: a 2-year feeding study in SD rats

This study evaluated the carcinogenicity and determined the no observed adverse effect level (NOAEL) of rhubarb extract in Sprague-Dawley (SD) rats over two years.SD rats (104 per group, equal males/females) were randomly assigned to a control (0 mg/kg BW) and three treatment groups (101, 405, and 1620 mg/kg BW). The extract was administered via diet for 104 weeks. Body weight, food consumption, urinalysis, hematology, organ-to-body weight ratios, and histopathology were analyzed. The 1620 mg/kg group showed significantly lower weight gain. Urinalysis revealed elevated ketones, nitrites, and reduced pH in1620 mg/kg BW group. Alkaline phosphatase (ALP) increased in 1620 mg/kg BW dose group of females, and blood glucose rose in 1620 mg/kg BW dose group of males. Activated partial thromboplastin time (APTT) was prolonged at 405 and 1620 mg/kg. Significant tubular pigment deposition was observed in kidneys at 405 and 1620 mg/kg, but no significant differences in tumor incidence were noted. The no observed adverse effect level (NOAEL) for rhubarb extract was 101 mg/kg BW, while the lowest observed adverse effect level (LOAEL) was 405 mg/kg BW. The liver and kidneys were primary toxicity targets. Rhubarb extract exhibited no carcinogenic potential in SD rats.