Analysis of soybean phospholipids based on liquid chromatography-ion trap-time of flight-mass spectrometry

Abstract

Using liquid chromatography-ion trap-time of flight-mass spectrometry to establish a soybean phospholipids(PL) analysis method, carry out comprehensive structural identification and quantitative analysis of soybean PL molecule species, and obtain soybean PL molecular composition and content data. The PL profiles of 10 soybean varieties cultivated in northeast China were determined by a hydrophilic interaction liquid chromatography-ion trap-time of flight-mass spectrometry(HILIC-ESI-IT-TOF-MS) system. The hydrophilic interaction liquid chromatography realized class separation of PLs, and ion trap-time of flight-mass spectrometry realized the estimation of head group type, fatty acyl structure, and substituent position. The identified PL molecule species were quantified using accurate mass extraction and internal standard method. A total of 101 PL molecular species from 11 classes were estimated in soybean seeds, including 20 phosphatidylcholines(PC), 15 phosphatidylethanolamines(PE), 17 phosphatidylinositols(PI), 12 phosphatidylglycerols(PG), 9 phosphatidic acids(PA), 6 phosphatidylserines(PS), 5 lysophosphatidylcholines(LPC), 5 lysophosphatidylethanolamines(LPE), 6 lysophosphatidylinositols(LPI), 4 lysophosphatidylglycerols(LPG) and 2 lysophosphatidicacids(LPA). The limits of detection for the target object were ≤ 60 ng/mL and R~2 were all >0.99. The total concentration of PL ranged from 6873.1 to 12 678.6 μg/g in detected soybeans. Generally, most of the detected soybean cultivars were great resources of PL, especially SN-29, SN-61, HN-40 and DN-690. The concentrations of PC and PE in the tested soybean were higher, followed by PI, PG, PA and PS. Among the lysophospholipids, the concentration of LPC was the highest, followed by LPE, LPI, LPG and LPA. The soybean PL component analysis method established based on the HILIC-IT-TOF-MS system can achieve good separation of various types of PL, and can accurately characterize the head group type, fatty acyl structure and substituent position of PL molecule species. The molecular composition and content data of soybean PL were obtained.