Simultaneous determination of bestatin and p-hydroxybestatin, a major metabolite, in human serum by gas chromatography mass spectrometry. Utilization of quantitative selected ion monitoring and deuterium labelled internal standard.

A specific and sensitive method for the simultaneous determination of bestatin and its major metabolite, p-hydroxybestatin in human serum has been developed by selected ion monitoring using the corresponding deuterated internal standards. The N-trifluoroacetamide-O-trimethylsilyl ether derivatives of the trideuteromethyl esters of bestatin and p-hydroxybestatin were suitable for quantitation by selected ion monitoring. The determination limit of these compounds by the present method is 1 ng ml−1 in human serum.