Determination of L-Carnitine and Acetyl-L-carnitine in Aspergillus oryzae- Fermented Rice Bran Product by Hydrophobic Derivatization–LC/ESI-MS/MS

抄録

L-Carnitine (CRN) and acetyl-L-carnitine (AcCRN) play several important roles, primarily energy production, and the ingestion of sufficient amounts of them is essential for human health. Rice bran (RB) fermented with Aspergillus oryzae (A. oryzae) is expected to be a CRN- and AcCRN-rich plant-based foodstuff. To prove this concept, a liquid chromatography (LC)/electrospray ionization-tandem mass spectrometry method was developed for measuring the CRN and AcCRN contents in the A. oryzae-fermented RB product. The derivatization using 1-aminonaphtharene was employed to enhance the LC retention of the analytes, which led to negligible matrix effects, satisfactory precision (all intra- and inter-assay relative standard deviations, ≤ 8.7%) and accuracy (all analytical recoveries, 98.2–102.7%). The CRN and AcCRN contents in the RB product after the fermentation for 46 h were 101 ± 8 and 23.8 ± 10.2 µg/g (mean ± standard deviation, 5 lots), which were tens and hundred times greater than those in the unfermented RB material (1.43 ± 0.09 and 0.0519 ± 0.0041 µg/g, respectively). Thus, the A. oryzae-fermentation was an effective approach for enriching the RB-based material with CRN and AcCRN, and the resultant product could be one of the most CRN- and AcCRN-abundant plant-based foodstuffs.