Analytical methods for determination of closantel enantiomers by HPLC and their residual elimination profiles in ten tissues of black goats

Abstract

Closantel is a halogenated derivative compound with a salicylanilide-base, broad-spectrum, potent anthelmintic against several types of trematodes, nematodes, and other external parasites. It is a racemate of an equimolar mixture of two enantiomers, mainly used in livestock farming. It is significant to develop the analysis methods of closantel enantiomers in animal tissues. In this study, a reliable, precise, and selective HPLC method was established to separate and determine closantel enantiomers in ten tissues of black goats. The mean recoveries for closantel enantiomers were between 70.0% and 93.8%, and the limits of quantification were 0.5 µg/g. The proposed method was successfully applied to investigate the distribution and residual elimination of closantel enantiomers in ten edible tissues of black goats following an intramuscular injection of 5 mg/kg body weight of closantel sodium. The results revealed that closantel was stereoselective, and the two closantel enantiomers were eliminated slowly, with half-lives ranging from 9 to 14 days in the tissues of black goats. These findings would support further evaluation of the enantioselective pharmacokinetics, pharmacodynamics, and toxicity of individual closantel enantiomers in food-producing animals.