An analytical strategy for identification of a somatotropin-like bioactive peptide by ion trap liquid chromatography/electrospray ionization tandem mass spectrometry after immuno-affinity purification from buffalo serum.

The use of growth hormones, such as native and recombinant somatotropins, is forbidden in the European Union (EU), but is legal in the USA. The misuse of recombinant bovine somatotropin in Italy is suspected for enhancing milk production, thanks to its availability on the illegal market. A synthetic bioactive peptide of 27 amino acids derived from bovine somatotropin was successfully tested in France and in southern Italy for scientific purposes, to stimulate milk production, both in cows and buffaloes. This somatotropin-like peptide (PEP-ST), suspected for illegal use in southern Italy, was synthesized by linking the 104-113 sequence of bovine somatotropin to the 323-339 sequence of ovalbumin. Herein, a method for detection and identification of the PEP-ST in buffalo serum is described; our strategy was based on the production of IgG anti-PEP-ST, used to synthesize an immuno-affinity column for peptide purification from buffalo serum, prior to analysis by ion trap liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). The immuno-affinity column was successfully used to purify in a single step the bioactive PEP-ST from buffalo serum samples spiked at 20, 50 and 200 microg/mL for confirmatory analysis. Ion trap LC/ESI-MS/MS identification was based on detection of a multi-charged molecular ion and its characteristic fragmentation pattern. No significant matrix interference was observed, accounting for method specificity. We consider this strategy to be a basic approach that could be improved in the perspective of the official control of illegal use of somatotropin and somatotropin-like compounds in buffalo breeding.