Abstract: Aqueous extracts of raw Pu-erh tea (7542) samples from the same batch obtained from the same producer with different storage times were prepared by vacuum freeze drying in this study and their characteristic components were detected by spectrophotometry and ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The experimental data were analyzed with principal component analysis (PCA) and cluster analysis (CA) to establish the characteristic components of Pu-erh tea aqueous extracts and a dendrogram for cluster analysis of raw Pu-erh tea samples stored for different times. The results showed that the contents of tea polyphenols, catechins and free amino acid of raw Puerh tea aqueous extracts decreased gradually with storage time of Pu-erh tea while flavones increased; the contents of total soluble sugars and caffeine showed an irregular fluctuation. A total of 107 substances were detected from raw Puerh tea aqueous extracts with different storage times by UPLC-MS/MS. Using PCA, the 26 characteristic components of raw Pu-erh tea aqueous extracts were determined to include citric acid, gallic acid, epicatechin, theanine, caffeine, and epigallocatechin gallate. Cluster analysis results indicated that the clustering of raw Pu-erh tea samples changed significantly after storage for 3 years and 8 years and that aqueous extracts of raw Pu-erh tea samples with similar storage times were more likely to be clustered.

Key words: raw Pu-erh tea, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), characteristic components, multivariate statistical analysis