Quantification of ergothioneine in Aspergillus oryzae-fermented rice bran by a newly-developed LC/ESI-MS/MS method

Abstract The ingestion of l -ergothioneine (EGT) is thought to provide health benefits. It is also expected that the fermented rice bran or rice with Aspergillus oryzae (A. oryzae) would be EGT-rich and easily available foodstuffs. Based on this concept, a liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) method was developed to identify and quantify EGT in the A. oryzae-fermented rice bran and rice. We optimized the derivatization protocol using 2-iodo-N-(8′-quinolinyl)acetamide, which improved the LC retention and ESI-MS/MS sensitivity of EGT. The pretreatment procedure and LC/ESI-MS/MS conditions were also optimized to achieve the sensitive (limit of quantification, 0.080 μg/g), precise (intra- and inter-assay relative standard deviations,