Citrus aurantium (bitter orange) extract: Safety assessment by acute and 14-day oral toxicity studies in rats and the Ames Test for mutagenicity

Regul Toxicol Pharmacol. 2017 Nov;90:318-327. doi: 10.1016/j.yrtph.2017.09.027. Epub 2017 Sep 28.


The primary active constituent in bitter orange extract (BOE) is p-synephrine. This study assessed the safety of a BOE standardized to 50% p-synephrine following short-term exposure to rats and by the Ames Test. Following 5000 mg/kg of the extract orally to female rats all animals survived. Administration at 2000 mg/kg to female rats for four days yielded no signs of toxicity. Five male and five female rats were administered the BOE at 0, 250, 500, 1000 and 2000 mg/kg/day for 14 days. No significant effects were observed at any dose with respect to body weights, food intake, absolute and relative organ weights, hematology, clinical chemistry, and pathology. Two male rats died after 2000 mg/kg with gastrointestinal impaction at necropsy. During week two of 1000 mg/kg and 2000 mg/kg/day, rats exhibited transient signs of repetitive burrowing of heads in the bedding material (hypoactivity) for about 15 and 45 min, respectively. The no-observed-effect-level (NOEL) was 500 mg/kg/day. The mutagenic potential was assessed at and up to the limit dose of 5000 μg/plate in a Salmonella typhimurium reverse mutation (Ames) test, performed in duplicate as a pre-incubation assay in the presence and absence of metabolic activation (S9). The BOE did not induce an increase in the frequency of revertant colonies at any dose in the five tester strains, and was therefore non-mutagenic.

Keywords: Ames Test; Bitter orange; Citrus aurantium; LD50; Reverse mutation assay; Safety; Salmonella typhimurium; p-synephrine.

MeSH terms

  • Administration, Oral
  • Animals
  • Biological Assay / methods
  • Citrus / chemistry*
  • Female
  • Gastrointestinal Tract / drug effects
  • Lethal Dose 50
  • Male
  • Mutagenesis / drug effects
  • Mutagenicity Tests / methods
  • Mutagens / toxicity*
  • No-Observed-Adverse-Effect Level*
  • Plant Extracts / toxicity*
  • Rats
  • Rats, Sprague-Dawley
  • Salmonella typhimurium / drug effects
  • Salmonella typhimurium / genetics
  • Synephrine / toxicity*
  • Toxicity Tests, Acute


  • Mutagens
  • Plant Extracts
  • Synephrine