Changes in Polyamine Content in Rice Bran due to Fermentation with Aspergillus oryzae Analyzed by LC/ESI-MS/MS Combined with Derivatization.

Many studies have demonstrated that the dietary supplementation of polyamines, especially spermidine (SPD), prevents age-related diseases. Rice bran is rich in polyamines and their amounts could be increased by fermentation with Aspergillus oryzae (A. oryzae). In this study, we developed a method for the determination of putrescine (PUT), SPD and spermine (SPM) in rice bran samples by liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) after derivatization with 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F). The derivatization improved the LC retention and ESI-MS/MS detectability of the polyamines, and consequently enabled precise and accurate quantification. Using this method, we found that the SPD content increased to 158% due to fermentation with A. oryzae, while the content of PUT and SPM decreased. SPD is known as the polyamine playing a central role in cell proliferation and growth, and therefore has health benefits. The fermented rice bran might be a good material for functional foods aimed at SPD supplementation.