## 3 Results and Discussion
### Characterization of Chemical Composition Using LC-Q-TOF/MS  
From the above results, LC-Q-TOF/MS analysis was performed using the representative extraction condition of 30% ethanol. This condition provided the best overall phenolic content and proved to be a reliable measure for antioxidative capacity. A total of eight  
Figure 1: Correlations between TPC, TFC, and radical scavenging effects of different conditions of \(E\). _globulus_ leaf extracts. (**a**) DPPH-ABTS, (**b**) TPC-TFC, (**c**) TPC-DPPH, (**d**) TFC-DPPH, (**e**) TPC-ABTS, and (**f**) TFC-ABTS.  
predominant phytochemicals (**1**-**8**) were confirmed from the base peak chromatogram (BPC) of the _E. globulus_ leaves extracted using 30% ethanol (Figure 2a). As shown in Table 3, the metabolites were identified by comparing the calculated error value between the observed and theoretical mass (\(m/z\)) in each mass gram of peaks as follows: salicylic acid \(\beta\)-D-O-glucurononide (**1**), chlorogenic acid (**2**), epicatechin (**3**), 2''-O-galloylhyperin (**4**), isoquercitrin (**5**), isorhapontin (**6**), quercetin (**7**), and quercetin-3-O-glucurononide (**8**).  
The abundant metabolites in the _E. globulus_ leaves were classified as phenolic acid, quercetin, stilbene derivatives, and epicatechin. Peak 1 (Figure 2b, \(t_{\rm R}=1.7\) min) showed a molecular ion peak [M + H]\({}^{+}\) detected at \(m/z\) 315.0721, which was identified as salicylic acid \(\beta\)-D-O-glucuronide (**1**) by comparison with the theoretical mass ([M + H]\({}^{+}=m/z\) 315.0716). Peak 2 (Figure 2c, \(t_{\rm R}=6.7\) min) was deduced as chlorogenic acid (**2**) by confirming its molecular and fragment ion peaks at [M + H]\({}^{+}=m/z\) 355.1014 and 163.0385, respectively. The fragment ion at \(m/z\) 163.0385 was typically observed as a caffe acid moiety, which is the result of a cleavage of the chemical bond with a quinic acid on its chemical structure. Peak 3 (Figure 2d, \(t_{\rm R}=7.8\) min) was confirmed as a signal of epicatechin (**3**), which possessed a molecular ion peak at [M + H]\({}^{+}=m/z\) 291.0057. Additionally, the epicatechin (**3**) from peak 3 was determined via confirmation of the error value with \(-4.12\) ppm and the retention time of the authentic compound. Peak 4 (Figure 2e, \(t_{\rm R}=17.0\) min) was verified as 2\({}^{\prime\prime}\)-O-galloylhyperin (**4**) with a reasonable error value of -2.27 based on the observed ion peak at [M + H]\({}^{+}=m/z\) 617.1129 and its theoretical mass of \(m/z\) 617.1143. Peak 6 (Figure 2g, \(t_{\rm R}=19.3\) min) presented a molecular ion [M + H]\({}^{+}\) at \(m/z\) 421.1502. A fragment ion at \(m/z\) 259.0964 was formed by the loss of a glucose moiety from its chemical structure. The remaining peaks 5, 7, and 8 were characterized as quercetin derivatives by having the fragment peak at \(m/z\) 303 assigned from quercetin. Specifically, peak 5 (Figure 2f, \(t_{\rm R}=17.3\) min) showed a major ion peak at [M + H]\({}^{+}=m/z\) 465.1021 by relying on the chemical formula of isoquercitrin (**5**) with C\({}_{21}\)H\({}_{20}\)O\({}_{12}\). Peak 7 (Figure 2h, \(t_{\rm R}=20.2\) min) exhibited a molecular ion peak at [M + H]\({}^{+}=m/z\) 449.1063. The observed ion peak corresponded to quercetin (**7**) as quercetin rhamnide by verifying the identical value of the exact mass with \(m/z\) 449.1084. Peak 8 (Figure 2i, \(t_{\rm R}=22.2\) min) was identified as quercetin-3-O-glucuronide (**8**) via the practical comparison between the observed and chemical masses at \(m/z\) 479.0796 and 479.0826, respectively. Based on these results, the eight metabolites (**1-8**) were tentatively assigned as the abundant metabolites of _E. globulus_ leaves.