Comprehensive discrimination of various grades of green tea by lipidomics combined with principal component analysis

The grades of Longjing green tea were discriminated using lipidomics based on ultra-high performance liquid chromatography-high-resolution accurate-mass tandem mass spectrometry (UHPLC-HR-AM/MS/MS). A total of 13 lipid classes and 100 molecule species were detected. High-grade Longjing green tea was characterized by elevated level of phospholipids and unsaturated fatty acids. Thirty lipid molecular species were selected as discriminatory markers for differentiating among the grades of Longjing green tea. Notably, two phosphatidylcholine (PC) isomers, PC 16:0/18:3 and PC 17:1/17:2, distinguished the grades of both MeiJiaWu (MJW) and YunQi (YQ) teas. Additionally, two triacylglycerol (TG) isomers, TG 18:1/18:2/18:3 and TG 18:2/18:2/18:2, differentiated the grades of MJW tea. Furthermore, high-grade tea exhibited lower ratios of n-6 to n-3 fatty acids and higher ratios of polyunsaturated fatty acid (PUFA) to saturated fatty acid (SFA), which indicated that high-grade tea had a superior nutritional profile. The findings provided a scientific basis for grading Longjing green tea and supporting the development of the tea industry and market.