Phosphatidylcholine, lysophosphatidylcholine (LPC), phosphatidylinositol, lysophosphatidylinositol (LPI), phosphatidylethanolamine, lysophosphatidylethanolamine (LPE), phosphatidic acid, and lysophosphatidic acid (LPA) contents were analyzed by phosphorus-31 nuclear magnetic resonance spectroscopy