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.

Isotope-coded derivatization based LC/ESI-MS/MS methods using a pair of novel reagents for quantification of hydroxycinnamic acids and hydroxybenzoic acids in fermented brown rice product.

Hydroxycinnamic acids (HCAs) and hydroxybenzoic acids (HBAs) are antioxidant phytochemicals found in rice and effective for the prevention of human diseases including cancer. FBRA, which is a functional food manufactured by fermenting brown rice and rice bran with Aspergillus oryzae, has been demonstrated to have chemopreventive effects against carcinogenesis in various organs. In this study, we developed methods for the relative and absolute quantification of ferulic acid, sinapic acid, caffeic acid, protocatechuic acid and syringic acid in the FBRA and raw material (RM; unfermented brown rice and rice bran) samples by LC/ESI-MS/MS combined with derivatization using a newly developed reagent, N-(2-aminoethyl)-4-(diethylamino)benzamide (ADB) and its deuterium-coded analog, d-ADB. For the relative quantification, the FBRA and RM samples were derivatized with ADB and d-ADB, respectively, then the resulting derivatives were mixed and subjected to LC/ESI-MS/MS; by this method, we found that the fermentation process significantly increased the free HCA and HBA contents. The HCA and HBA contents in the FBRA were also determined, in which the d-ADB-derivatized standards of known amounts were used as the internal standards. The ADB-derivatization enabled the sensitive and specific detection, and the use of d-ADB significantly improved the assay precision.