Safety evaluation and biochemical behavior of monotertiarybutylhydroquinone

The safety of monotertiarybutylhydroquinone as an oil‐soluble food grade antioxidant was evaluated in acute studies with rats and dogs, in subacute feedings in rats, in rat reproductive efficiency and placental transfer studies, and in subacute feedings with monotertiarybutylhydroquinone heated in vegetable oil. In lifetime feedings in rats and 2 year feedings in dogs, wt gain, feed consumption, behavior, mortality, hemograms, clinical chemistries, gross, microscopic, and electron microscopy were evaluated. There were no toxic or untoward effects. Monotertiarybutylhydroquinone was handled similarly by rats, dogs, and humans. Rats eliminated single oral 0.1–0.4 g/kg doses mostly in the urine in 3–4 days as the 4‐0‐sulfate (57–80%) and the 4‐0‐glucuronide (4%) and with 4–12% unchanged. 2,3,5,6‐ 14 C‐Monotertiarybutylhydroquinone was eliminated similarly with <0.1% as 14 CO 2 and <0.2% remaining in the animal after 4 days. Oral 0.1 g/kg doses to dogs gave a somewhat higher glucuronide contribution. The elimination pattern was little altered in long term feedings. Humans eliminated 0.002 g/kg single doses (high fat vehicle) almost completely in the urine in 2–3 days, with <0.1% unchanged, 73–88% as the 4‐0‐sulfate, and 15–22% as the 0‐glucuronide. Monotertiarybutylhydroquinone residues in most tissues of long term animals were below lower detection limits or negligible. Monotertiarybutylhydroquinone did not induce liver microsomal mixed function oxidases in short and long term rat and dog feedings. The feeding studies and comparative biochemical studies showed monotertiarybutylhydroquinone to be safe for its intended use.