Identification and determination of isoflavones in germinated black soybean sprouts by UHPLC−Q-TOF-MS mass spectrometry and HPLC-DAD.

Ultra-performance liquid chromatography coupled with electrospray ionization tandem quadrupole time-of-flight mass spectrometry (UHPLC−Q-TOF-MS) and HPLC-DAD with an ultrasonic extraction method was developed for qualitative and quantitative compositions and contents in black soybean sprouts. Operational conditions of ultrasonic extraction were optimized by single-factor experiment. Phytochemical compositions of black soybean sprouts were identified by UHPLC−Q-TOF-MS in positive ion mode. A total of 23 compounds were tentatively characterized and identified by means of accurate mass and characteristic fragment ions. Among of them, the six isoflavones in different germinated black soybean sprouts were further quantified by HPLC-DAD. The results indicated that the calibration curves showed good linearity (r2 > 0.9994). The intra-day and inter-day precision variations were less than 1.65% and 1.73%, respectively. The recoveries were in the range of 94.95-106.45%. The results indicated that the maximum amounts of isoflavones were produced on the fourth to fifth day germinated black soybean sprouts. [ABSTRACT FROM AUTHOR]