Characterization of Silybum marianum triacylglycerol regioisomers using accurate mass quadrupole time of flight mass spectrometry

Abstract Milk thistle (Silybum marianum) is a medicinal plant commonly used as a food supplement for liver protection against hepatitis C virus. The fruits are very rich in lipids (>30%); however, their chemical structures are not well characterized. In this investigation, dry fruits were extracted using CO2 supercritical fluid extraction to obtain the crude lipid components. Triacylglycerols (TAGs) were isolated from the crude lipid extract using high-performance thin layer chromatography. Fatty acid composition of the purified TAGs was identified as their fatty acids methyl esters (FAMES) using gas chromatography mass spectrometry. Regioisomers of TAGs and their relative abundances were determined using accurate mass ultra-high-performance liquid chromatography quadrupole time of flight mass spectrometry both in the full scan and in MSMS electrospray ionization modes. Major identified fatty acids were 18:2, 18:1 and 16:0. Twenty-six different TAGs were identified with LLL, OLL, PLL, LOO and PLO as the major components.