Preparation and dietary effects of ethoxyquin hydrochloride

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Abstract
Ethoxyquin (EQ, 1,2‐dihydro‐6‐ethoxy‐2,2,4‐trimethylquinoline) was purified and converted to a crystalline, stable ethoxyquin hydrochloride (EQ‐HCI). The readily available (technical grade) oily EQ reacted with concentrated hydrochloric acid (HCl) and precipitated as a crystalline salt (EQ‐HCI) in acetone, leaving most of the impurities in solution. The regenerated free base (EQ) from the EQ‐HCI was further purified by silica‐gel column chromatography to remove several minor contaminants, and the pure unstable EQ was immediately converted into a pure stable salt (EQ‐HCI). The dietary administration of EQ‐HCI, 0.25 or 0.5% in the feed, induced hepatic and intestinal thiols in mice and provided protection against toxic doses of pyrrolizidine alkaloids. The LD50 values of the 0.125 and 0.25% EQ‐HCl‐pretreated mice were 94.0 and 98.5 mg/kg, respectively, compared to that of controls, 71.3 mg/Mg. The EQ‐HCI‐supple‐mented feed appeared to be more palatable, but other effects, such as the hepatic hypertrophy, the tissue thiol induction, and the protective effects, were comparable1 to those of unpurified EQ.