Fragmentation patterns of phospholipids have been thoroughly investigated in previous studies. However, most studies only concentrate on these patterns for several phospholipids in single ion mode (positive or negative ion mode); this has not provided a systematic summarization for more phospholipids. Because phospholipidomics studies require high throughput screening of the target phospholipids, the necessity for rapid identification schemes for these compounds becomes obvious. Fragmentation patterns of five major types of phospholipids, including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI) and sphingomyelins (SM), in different ion modes at several elevated collision energies (10–50 eV) have been studied by ultra-high-performance liquid chromatography electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/ESI-Q-TOFMS). The different characteristic ions of phospholipids in ESI (±) modes, three possible patterns ([RCO]+, [RCOO−]−, and neutral ion R′CHCO) of fatty acyl chains in ESI (±) modes, and changes in the abundance ratios of the sn-1/sn-2 carboxylate anions of phospholipids at different collision energies, which can be used to quickly identify the positions of fatty acyl chains of phospholipids, were revealed. Fragmentation patterns of five major types of phospholipids were systematically summarized. This summary provides reference tools for the rapid identification of phospholipids and the opportunity to obtain complementary and more comprehensive results in future phospholipidomics studies.
Lipase-catalyzed synthesis of mono- and diesters of 3-O-β-D-galactopyranosyl-sn- glycerol (β-GG) with caproic acid was performed in acetone. The simultaneous production of 1(6’)-monoesters and 1,6’-diesters of β-GG was achieved in this reaction. In order to improve the yield of β-GG esters, four process parameters, enzyme concentration (15 ∼ 25 mg/mL), and substrate molar ratio (caproic acid: β-GG= 1.60 ∼ 2.00 mmol: 0.10 mmol), reaction temperature (40 ∼ 60 °C), and reaction time (8 ∼ 12 h), were optimized via response surface methodology (RSM) employing a three-level-four-variable central composite design. Results showed that enzyme concentration had the most significant (p < 0.0001) effect on the synthesis of β-GG esters. The optimal reaction conditions in acetone were given as follows: Novozyme435 concentration 18.65 mg/mL, molar rate of caproic acid to β-GG 19.46:1, reaction temperature 48 °C, and reaction time 9.83 h. The yield of β-GG esters reached 88.08% under above optimized conditions, which was very close to the predicted value 87.95%. The molar ratio of monoester to diesters was 0.39:0.61. β-GG esters with other fatty acyl chains were synthesized based on the optimized conditions. In vitro antitumor activity indicated that the antitumor activity of β-GG esters was dependent on the nature of fatty acids, such as the length of acyl chain, the degree of saturation, as well as the number of acyl chain.
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