Cyclic phosphatidic acid (cPA) is a simple lipid containing a fatty acid attached at the sn-1 position and a cyclic phosphate ring structure at the sn-2 and sn-3 positions of the glycerol backbone. The pharmacological effects of cPA have been demonstrated in several diseases such as cancer and neuropathic pain; however, the composition of the molecular species of cPA in relative to other lipid species in biological samples is still unclear. Recently, hydrophilic interaction liquid chromatography (HILIC) has demonstrated the ability to perform lipidomic analyses of biological samples. In the present study, we developed the quantitative measurement of cPA and its related lipid species, such as lysophosphatidic acid (LPA) and lysophosphatidylcholine (LPC), in rat serum using HILIC equipped with tandem-mass spectrometry (MS/MS). The lipid analysis using HILIC-MS/MS system demonstrated high linearity and reproducibility. The modified Bligh and Dyer method using citric acid was showed high efficiency on the extraction of cPA and LPA without contamination of artificial products. In rat serum, cPA and LPC contained more saturated fatty acids such as palmitic acid and stearic acid than unsaturated fatty acids, whereas LPA and phosphatidylcholine more contained unsaturated fatty acids than saturated fatty acids. The analytical methods for measuring cPA and its related lipid species in the present study will aid the analysis of their metabolism.

环状磷脂酸（cPA）是一种简单的脂质，其脂肪酸附着在sn -1位置，环状磷酸酯环结构位于sn -2和sn甘油主链的-3位。cPA的药理作用已在多种疾病中得到证实，例如癌症和神经性疼痛。然而，相对于生物样品中其他脂质种类，cPA分子种类的组成仍然不清楚。最近，亲水相互作用液相色谱法（HILIC）已证明能够对生物样品进行脂质组分析。在本研究中，我们开发了使用配备串联质谱（MS / MS）的HILIC在大鼠血清中对cPA及其相关脂质物种（如溶血磷脂酸（LPA）和溶血磷脂酰胆碱（LPC））进行定量测量的方法。使用HILIC-MS / MS系统进行的脂质分析显示出高线性和可重复性。使用柠檬酸改进的Bligh和Dyer方法显示出对cPA和LPA的萃取效率高，而不会污染人造产物。在大鼠血清中，cPA和LPC所含的饱和脂肪酸（如棕榈酸和硬脂酸）比不饱和脂肪酸要多，而LPA和磷脂酰胆碱所含的不饱和脂肪酸比饱和脂肪酸要多。本研究中测量cPA及其相关脂质种类的分析方法将有助于分析其代谢。