Mahmoud A. Saleh
Texas Southern University, USA
Title: Mass Spectrometry Regiospecific Analysis of neutral triacylglycerols
Biography
Biography: Mahmoud A. Saleh
Abstract
Different mass spectrometry ionization techniques were compared for their use in regiospecific analysis of neutral triacyglycerol (TAG) in different samples of seeds oil. Atmospheric pressure chemical ionization, atmospheric pressure photo ionization, electro spray ionization, ion trap and QTOF accurate mass were used in the LCMS experiments. Electron ionization, chemical ionization and QTOF accurate mass were used in GCMS experiments. MSMS QTOF and MSMS1-n ion trap experiments were used for structural conformation. Seed oil of Silybum marianum and 9 species of the Apiaceae family (dill, caraway, cumin, coriander, anise, carrot, celery, fennel and Khella) were used in this investigation. Results for regiospecific analysis showed a non-random fatty acids distribution in both S. marianum and Apiaceae seeds. Petroselinic acid was predominantly located at the sn-1 and sn-3 positions in carrot, celery and parsley seed oils, while it was mainly at the sn-2 position in caraway seed oil. The distribution of linoleic acid was opposite to that of petroselinic acid. Oleic acid was mostly located at the sn-2 position, except for caraway, where it was evenly distributed between the sn-1(3) and sn-2 positions. Both the saturated FA, palmitic and stearic acid, were located mainly at the sn-1(3) position. Based on our finding, it can be concluded that fragmentation pattern for TAGs follow the following scheme: The most abundant ions observed in the mass spectra of TAG are positive ions containing two complete fatty acid chains and those containing only one complete chain corresponding to the loss of one or two fatty acids respectively. Two ions were found corresponding to the ion remaining after the loss of one acyloxy group from the molecular ion [M-RCOO]+, and the other corresponding [M-RCOOH]+. If the three fatty acids are different, three different [M-RCOO]+ and [M-RCOOH]+ ions corresponding to the loss of each different acyloxy group. However, due to steric and electronic property, the loss of the fatty acid located in the sn2 is energetically less favorable than one at the end positions (sn1 and sn3). Therefore, ions corresponding from the loss of fatty acids from the sn1 and sn3 positions are much more abundance the ion corresponding to the loss of fatty acid at the sn2 position.