Determination of bestatin in serum by high-performance liquid chromatography with fluorescence detection

A simple method for the determination of bestatin and its major metabolite in man, p-hydroxybestatin, in human serum was investigated; the method employs high-performance liquid chromatography with fluorescence detection. Bestatin and p-hydroxybestatin are oxidized to phenylacetaldehyde and p-hydroxyphenylacetaldehyde, respectively, with periodate, which are then converted into fluorescent compounds with 4,5-dimethoxy-1,2-diaminobenzene. The compounds are separated by reversed-phase chromatography on LiChrosorb RP-18. The detection limits of bestatin and p-hydroxybestatin are 0.2 and 0.4 microgram/ml serum, respectively. This method permits the precise determination of bestatin in serum (20 microliter) from patients administered bestatin. p-Hydroxybestatin in serum can not be measured by this method because of its low concentration (less than the detection limit).