Proline derivatives in fruits of bergamot (Citrus bergamia Risso et Poit): Presence of n -methyl- l -proline and 4-hydroxy- l -prolinebetaine

The content of proline and various compounds deriving from its metabolism (4-hydroxy-l-proline, N-methyl-l-proline, N,N-dimethylproline, and 4-hydroxy-l-prolinebetaine) was determined in fruits and seeds of Bergamot (Citrus bergamia Risso et Poit), growing in the Calabria region (South Italy). A HPLC-ESI-tandem mass spectrometry method, which allowed rapid determination of l-proline, 4-hydroxy-l-proline, N-methyl-l-proline, N,N-dimethylproline, and 4-hydroxy-l-prolinebetaine in juice and extracts of bergamot fruit with minimum sample preparation and short analysis time (about 10 min), is presented. Proline and 4-hydroxy-l-proline levels in the samples were also determined by HPLC analysis with fluorescence detection and the results compared to those obtained with HPLC-ESI-tandem mass spectrometry. For the first time, the presence of N-methyl-l-proline and 4-hydroxy-l-prolinebetaine in the fruits of a plant of the Citrus genus is reported. © 2010 American Chemical Society.