Identification of Buctopamine and Mebuctopamine, a β2 Receptor Agonist and Its Metabolite, in Swine Hair and Feed Additives

4-[2-(t-Butylamino)-1-hydroxyethyl]phenol (buctopamine, 4), a new β₂ receptor agonist (β₂-agonist), was found to be an adulterant in feed additives for swine in Taiwan, where using β₂-agonists in food-production Animals is prohibited. Buctopamine and its metabolite, 4-[2-(t-butylamino)-1-hydroxyethyl]-2-methoxyphenol (mebuctopamine, 2), were detected in swine hair specimens. Authentic compounds 2 and 4 were synthesized with 98.6% and 97.7% purity, respectively, as Reference Standards for analysis, and both compounds were more hydrophilic than ractopamine and clenbuterol. In a preliminary pharmacological evaluation, compounds 2 and 4 exhibited moderate human β₂ receptor binding affinity and did not show significant affinities for the human α₁, α₂, β₁, and β₃ receptors. After addition of compounds 2-4 into the β₂-agonist library, a multiresidue analysis of 26 β₂-agonists by using triple quadrupole LC/MS/MS for routine screening conducted by regulatory authorities was established, in which the common limits of quantification for the 26 β₂-agonists in swine feed and hair are 10 and 25 ng/g, respectively. In addition, the illegal use of buctopamine (4) has been effectively prevented. The results of this study are also useful for controlling the illegal use of new β₂-agonists in food-production Animals.

feed additive; hair; identification; metabolite; β2-agonist.