Chemical Composition Analysis of Three Green Teas from Guizhou Province by UPLC-QE-Orbitrap-MS

In this study, ultra-performance liquid chromatography coupled with quadrupole-Orbitrap high-resolution mass spectrometry (UPLC-QE-Orbitrap-MS) was employed for non-targeted chemical profiling of three representative green teas from Guizhou Province, namely Meitan Cuiya, Duyun Maojian, and Fenggang Zinc-Selenium tea. The effects of two pretreatment methods, hot water extraction and 70% methanol extraction, on compound detection were systematically compared. Qualitative identification was achieved based on accurate mass measurements, MS/MS fragmentation patterns, and database matching, leading to the identification of a broad spectrum of bioactive constituents classified as phenolic acids, flavonoids, amino acids, and carbohydrates. The results showed that the three tea varieties share both commonalities and distinct differences in their chemical compositions. A total of 40 compounds were found to be common to all three types of tea, with chlorogenic acid, gallic acid, trifolin, catechin, and epigallocatechin gallate being the predominant compounds. Notably, catechins exhibit consistently high MS response intensities under various extraction conditions, underscoring their role as core components constituting the material basis of these teas. Meanwhile, each tea variety possesses its own characteristic compounds. For instance, in aqueous extracts, fraxin was uniquely identified in Meitan Cuiya, five compounds including kaempferol-3-O-rhamninoside were exclusively found in Duyun Maojian, and four compounds including (S)-10-hydroxycamptothecin were uniquely detected in Fenggang Zinc-Selenium tea. Regarding extraction efficiency, aqueous extracts yielded a higher number of identified compounds compared with methanolic extracts. Venn diagram analysis further revealed that Meitan Cuiya and Duyun Maojian shared a greater number of compounds, indicating closer chemical resemblance, whereas Fenggang Zinc-Selenium tea exhibits relatively fewer shared compounds with the other two varieties, suggesting a more distinctive chemical profile. The established method offers the advantages of high throughput, high resolution, and broad polarity coverage, enabling systematic elucidation of both similarities and differences in chemical compositions among tea varieties. This study provides a scientific basis for the quality evaluation, variety discrimination, and geographical origin traceability of Guizhou green teas.