## 3 Results and Discussion
#### 3.1.7 Flavonoids  
Previous studies reported the presence of isoflavenes and acylated/methoxylated apigenin and luteolin-O/C-glycosides in cucumber [28; 29], while flavonoid-O/C-glycos were reported in both species [3; 4; 30]. In this study, 24 flavonoids were detected and tentatively identified in both species, including flavones, flavonoids, and isoflav. C-glycosides were recognized by MSn ions corresponding to sugar ring cleavage, unlike O-glycosides, which showed intact release of the dehydrated sugar. Aglycones were differentiated based on their typical RDA fragments [31]. Identification was guided by GNPS-based networking, which allowed extrapolating peaks' annotations to unknown compounds, as observed in clusters B and C, in positive and negative MNs, respectively (Figure S1 and Figure 2).  
_Acylated flavonoids_ were detected in peaks 52, 54, 61, 62, 66, 67, and 71 (Table 1), in which cucumber was more abundant in aromatic, i.e., feruloyl (C\({}_{10}\)H\({}_{8}\)O\({}_{3}\), 176 amu) or coumaroyl (C\({}_{9}\)H\({}_{6}\)O\({}_{2}\), 146 amu), acylated flavones, whereas bottle gourd was enriched with flavone and flavonoids acylated with aliphatic, i.e., malonyl (C\({}_{3}\)H\({}_{2}\)O\({}_{3}\), 86 amu) or acetyl (C\({}_{2}\)H\({}_{2}\)O, 42 amu), moieties. These differential metabolomics results could aid in annotating acetyl transferase enzyme by correlating metabolite data with gene expression data. For example, peak 54 was identified as iso/vitexin-O-couamroylhexoside, which was previously reported in cucumber [28]. The precursor ion detected at [M+H]\({}^{+}\) 741.2041, C\({}_{36}\)H\({}_{37}\)O\({}_{17}\)\({}^{+}\) showed fragments at \(m/z\) 595, C\({}_{27}\)H\({}_{31}\)O\({}_{15}\)\({}^{+}\) [loss of coumaroyl, 146 amu], \(m/z\) 433 for iso/vitexin, C\({}_{21}\)H\({}_{21}\)O\({}_{10}\)\({}^{+}\) upon loss of O-hexosyl moiety, followed by MSn ions for C-hexosyl ring cleavage and aglycone RDA at \(m/z\) 415, \(m/z\) 397, \(m/z\) 313 and \(m/z\) 283 (Figure S8).  
_Methoxylated flavonoids_ were detected abundantly in bottle gourd fruit as in peaks 55, 58, 60, 62, 63, 64, 66, 67, and 71 (Table 1), identified based on the neutral loss of one or more methyl (-CH\({}_{2}\), 14 amu) / methoxyl (-OCH\({}_{2}\), 30 amu) moieties. For example, peak 62 was identified as isorhametin-O-malonylhexoside at [M+H]\({}^{+}\) 565.1186, C\({}_{25}\)H\({}_{25}\)O\({}_{15}\)\({}^{+}\) and was reported for the first time in both species (Figure S9). The precursor ion yielded fragments at \(m/z\) 479 [M+H-malonyl]\({}^{+}\), \(m/z\) 317, C\({}_{16}\)H\({}_{13}\)O\({}^{+}\) for isorhametin post deglycosylation followed by demethylation at \(m/z\) 303, C\({}_{15}\)H\({}_{11}\)O7, dehydration at \(m/z\) 285, C\({}_{15}\)H\({}_{9}\)O\({}_{6}\)\({}^{+}\) and finally RDA fragments at \(m/z\) 229, \(m/z\) 151 and \(m/z\) 127 [32]. To our knowledge, this is the first report of di/methoxylated flavonoid-O-acylated hexoside in _L. scieraria_, as in peaks 64, 66-69, and 71 (Table 1).  
Such a mixture of flavonoids promotes the various health effects of both species, since acylation and methoxylation are known to impart structural and functional modifications that improve flavonoids' bioactivity by increasing their lipophilicity and intracellular bioavailability, thus exhibiting better receptor/ligand binding compared to their non-acylated/methoxylated analogues, as observed in cancer chemoprevention and anti-acetylcholine esterase activities [20; 33; 34; 35].