# Metabolite Analysis of Hangzhou Gongmei White Tea of Different Varieties
## 3 Results and Discussion
### Differential Analysis of Non-Volatile Metabolites  
A total of 3690 non-volatile metabolites were identified (Table S2). PCA was performed on the abundance levels of the different metabolites (Figure 4a). The distance between FD and YS was found to be relatively close, with the four varieties distributed in different quadrants. The OPLS-DA method was then utilised to construct a discriminant model (Figure 4b), which enabled the distinction of the four varieties, with R2Y and Q2 values of 0.999 and 0.993, respectively. The model was subjected to 200 prediction analyses, which revealed that it does not demonstrate overfitting (Figure 4c). The VIP \(>\) 1 and \(p\)-value \(<\) 0.05 criteria were used to identify 997 differential metabolites (Table S3). According to the HMDB (Human Metabolome Database) classification, only 753 metabolites were identified (Figure 4d), which were divided into 11 categories: flavonoids (180), prenol lipids (138), organooxygen compounds (78), carboxylic acids and derivatives (49), fatty acyls (46), steroids and steroid derivatives (29), cinnamic acids and derivatives (27), isoflav (22), benzene and substituted derivatives (21), glycerophospholipids (13), and others (150). The differential metabolite expression levels were found to be highest in JK, while they were lowest in YS (Figure 4e). Figure 4: Analysis of non-volatile compounds in HGW. (**a**) PCA chart; (**b**) OPLS-DA (R2Y = 0.999, Q2 = 0.993) chart; (**c**) cross-validation by 200-time permutation test (R2 = 0.261, Q2 = \(-\)0.772); (**d**) HMDB classification of differential non-volatile metabolites; (**e**) the expression levels of different types of non-volatile metabolites; (**f**) the top 30 non-volatile metabolites with the highest VIP values. A significant disparity in the expression levels of diverse metabolic types was identified. The expression levels of flavonoids, phenol lipids, organooxygen compounds and isoflavoids were all highest in JK. Conversely, the highest expression levels of carboxylic acids and derivatives and glycerophospholipids were observed in FD, while the lowest expression levels of flavonoids and isoflavoids were seen in this sample. The expression levels of fatty acids, steroids and steroid derivatives, cinnamic acid and its derivatives, benzene and its substituted derivatives, and others were the highest in LJ, while the expression levels of carboxylic acids and their derivatives and glycerophospholipids were the lowest. The lowest expression levels of various metabolites, including phenol lipids, organic oxygen compounds, fatty acids, steroids and steroid derivatives, cinnamic acid and its derivatives, benzene and its substituted derivatives, and others, were observed in YS. Among the top 30 metabolites with the highest VIP values (Figure 4f), phenol lipids and flavonoid glycosides exhibited the greatest diversity, with nine and eight species, respectively. It is evident that there were substantial variations in the specific metabolites present among the various varieties. Spring white tea has been found to contain significant levels of kaempfer and myricetin [51], and their derivatives were observed to demonstrate varied responses across different varieties in this study. In JK, several flavonoids, including myricetin 7-(6''-galloylglucoseoside), quercetin 3-arabinoside 7-glucoside, kaempfer 3-sphroside 7-glucuronwide, kaempfer 7-(6''-galloylglucose), and isornhametin 7-glucoside, were found to be higher in abundance than in other varieties. Tagopogonasaponin B, (1S, 2R, 4R, 8S)-p-menthane-2,8,9-triol-9-glucoside, and lucyoside J were phenol lipid metabolites present at a significantly higher level in FD compared to in other varieties. Kaempfer 3-neohesperidoside-7-(2''-p-coumarinmiribioside) and kaempfer 3-O-rhamninoside were significantly higher in LJ than in other varieties. There are different types of flavonoid glycosides. In this study, the eight flavonoid glycosides were different from those screened in Fujian white tea [52,53].