# Metabolite Profiling of _Christia__vevertilionis_ Leaf Metabolome via Molecular Network Approach
## 3 Results and Discussion
#### 3.1.1 Phenolic Acids  
Visual inspection of the generated MNs in both ion modes revealed the presence of 3 distinct clusters (A, M, and N) and 2 \"self-loop\" nodes belonging to phenolic acids (Figure 2). In negative ion mode, the classification of these compounds was more specific since the different types of subgroups of the phenolic acids were separated from each other. Initially, automated GNPS spectral library matching on the spectral node in Cluster A with a precursor ion at \(m/z\) 344.134 [M + NH\({}_{4}\)]\({}^{+}\) permitted the annotation of a known phenolic acid glycoside molecule, namely, \(p\)-cumaric acid 4-O-glucose. In order to propagate the annotation of the connected nodes forming the molecular family of Cluster A, a detailed inspection of MS/MS fragmentation patterns was carried out. A total of 9 phenolic acids were identified, consisting of phenolic acid esters (**2**, **7**, **11**, and **15**) and phenolic acid glycosides (**10**, **13**, **14**, **17**, and **22**). All the phenolic acids identified in Cluster A were in the form of their ammonium adduct ions, [M + NH\({}_{4}\)]\({}^{+}\). The four nodes with precursor ions at \(m/z\) 360.150 [M + NH\({}_{4}\)]\({}^{+}\), 270.155 [M + NH\({}_{4}\)]\({}^{+}\), 356.155 [M + NH\({}_{4}\)]\({}^{+}\), and 312.165 [M + NH\({}_{4}\)]\({}^{+}\) were identified as phenolic acid esters. A node with a precursor ion at \(m/z\) 360.150 [M + NH\({}_{4}\)]\({}^{+}\) was putatively characterized as caffeoyl glucoside (2), the structural isomer of caffeic acid 4-O-glucose (**14**), which differed by the position of glucoside moiety attached to the caffeic acid parent structure. Specifically, its MS/MS data showed the characteristic fragment ion of a dehydrated caffeic acid moiety at \(m/z\) 163 for [(M+NH\({}_{4}\))-NH\({}_{3}\)-C\({}_{6}\)H\({}_{12}\)O\({}_{6}\)]\({}^{+}\), which resulted from the direct losses of ammonia and an intact glucoside moiety. Furthermore, it also generated a fragment ion assignable to the 3,4-dihydroxydiphenyl moiety at \(m/z\) 109 for [(M+NH\({}_{4}\))-NH\({}_{3}\)-C\({}_{6}\)H\({}_{12}\)O\({}_{6}\)-C\({}_{3}\)H\({}_{2}\)O]\({}^{+}\), after losing 54 Da from the transition ion at \(m/z\) 163. This was in agreement with the structural characteristic of caffeic acid esterified with one glucoside moiety at the carboxyl group. For the node with a precursor ion at \(m/z\) 270.155 [M + NH\({}_{4}\)]\({}^{+}\),  
Figure 2: Molecular family of phenolic acids putatively identified from Cluster A in positive ion mode and Clusters M, N, and “self-loop” nodes in negative ion mode. Red dotted circles represent proposed new structures. the compound was identified as caffeoylglycolic acid methyl ester (7). The compound showed a fragment ion for a dehydrated caffeic acid moiety at \(m/z\) 163 for [(M+NH\({}_{4}\))-NH\({}_{3}\)-C\({}_{3}\)H\({}_{6}\)O\({}_{3}\)]\({}^{+}\), which resulted from the losses of ammonia and a glycolic acid methyl ester moiety and a characteristic 3,4-dihydroxyphenyl fragment ion at \(m/z\) 109, all of which provided evidence that the caffeic acid was esterified with a glycolic acid methyl ester moiety. The node with a precursor ion at \(m/z\) 356.155 [M + NH\({}_{4}\)]\({}^{+}\) was characterized as \(p\)-coumaroylquinic acid (**11**) based on the characteristic fragment ion for a dehydrated quinic acid moiety at \(m/z\) 175 for [(M+NH\({}_{4}\))-NH\({}_{3}\)-C\({}_{9}\)H\({}_{8}\)O\({}_{3}\)]\({}^{+}\), which resulted from the losses of ammonia and a coumaroyl moiety, followed by decarboxylation of the carboxylic acid group, giving rise to a fragment ion at \(m/z\) 131. Another node with a precursor ion at \(m/z\) 312.165 [M + NH\({}_{4}\)]\({}^{+}\) (**15**), a mass difference of 42 Da from that of **7**, was tentatively proposed as an isopropyl derivative of **7**.