## 3 Results and Discussion
### Grapefruit Polyphenol-Rich Extract Composition
#### 3.2.2 Phenolic Compounds' Identification and Quantification
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Phenolic Compound** & **GF-CE** & **GF-PE** \\ \hline \multicolumn{3}{c}{Hydroxycinamic acids} \\ \hline Chlorogenic acid & 3.88 \(\pm\) 0.21 \({}^{\text{a}}\) & 11.22 \(\pm\) 0.09 \({}^{\text{b}}\) \\ Caffeic acid & 7.48 \(\pm\) 0.40 \({}^{\text{b}}\) & 43.83 \(\pm\) 0.61 \({}^{\text{a}}\) \\ p-Coumaric acid & 12.92 \(\pm\) 0.52 \({}^{\text{b}}\) & 52.50 \(\pm\) 0.45 \({}^{\text{a}}\) \\ Ferulic acid & 50.99 \(\pm\) 1.03 \({}^{\text{b}}\) & 227.89 \(\pm\) 2.15 \({}^{\text{a}}\) \\ \hline \multicolumn{3}{c}{Hydroxycbenzoic acids} \\ \hline Gallic acid & 2.86 \(\pm\) 0.01 & n.d. \\
3.4-Dihydroxybenzoic acid & 11.63 \(\pm\) 0.18 \({}^{\text{b}}\) & 24.52 \(\pm\) 0.08 \({}^{\text{a}}\) \\ Methyl gallate & 0.43 \(\pm\) 0.00 \({}^{\text{a}}\) & 0.12 \(\pm\) 0.01 \({}^{\text{b}}\) \\ Ellagic acid & 2.32 \(\pm\) 0.00 \({}^{\text{b}}\) & 3.15 \(\pm\) 0.03 \({}^{\text{a}}\) \\ Saponarin & 1.29 \(\pm\) 0.00 & n.d \\ \hline \multicolumn{3}{c}{Flavonoids} \\ \hline Rutin & 6.43 \(\pm\) 0.24 \({}^{\text{a}}\) & 3.71 \(\pm\) 0.23 \({}^{\text{b}}\) \\ Narinutin & 15,026.94 \(\pm\) 6.05 \({}^{\text{b}}\) & 28,729.79 \(\pm\) 7.41 \({}^{\text{a}}\) \\ Hesperidin & 667.73 \(\pm\) 1.53 \({}^{\text{a}}\) & 285.58 \(\pm\) 1.98 \({}^{\text{b}}\) \\ Diosmin & 62.34 \(\pm\) 0.81 \({}^{\text{b}}\) & 80.80 \(\pm\) 0.78 \({}^{\text{a}}\) \\ Quercetin & 0.62 \(\pm\) 0.01 \({}^{\text{b}}\) & 1.14 \(\pm\) 0.11 \({}^{\text{a}}\) \\ Naringenin & 7716.13 \(\pm\) 2.36 \({}^{\text{b}}\) & 48,609.40 \(\pm\) 9.16 \({}^{\text{a}}\) \\ Hesperidin & 3.00 \(\pm\) 0.02 \({}^{\text{b}}\) & 4.08 \(\pm\) 0.31 \({}^{\text{a}}\) \\ \hline \hline \end{tabular} n.d., not detected.  
\end{table} 
Table 3: Quantification of the phenolic compounds (ug/g DE) in the GF peels’ polyphenol-rich extracts (GF-CE and GF-PE). Values represent the mean \(\pm\) standard deviation. Different letters mean significant differences between the extracts for the same phenolic compound (\(p\) < 0.05). 100 \({}^{\circ}\)C for 4 h [78]. In our results, it was noticed that the complete decomposition of gallic acid was observed in the GF-PE, which may be due to the previous 3 h in hydrodistillation. This explains the decline in the antioxidant, antimicrobial, and anti-inflammatory activities of the GF-PE. The GF-CE was prepared and evaporated at a temperature not exceeding 45 \({}^{\circ}\)C, enabling the stability of heat-sensitive compounds, which allows for the synergistic activity with the flavonoid glycosides and phenolic acids present even at a lower concentration than that of the GF-PE (obtained after EO extraction) to perform higher antioxidant, antimicrobial, and anti-inflammatory activities [79; 80; 81]. Furthermore, it is crucial to account for the total activity of polyphenol-rich extracts, influenced by the synergistic or antagonistic interactions among their constituents. Typically, phytochemicals are recognized for conferring human health benefits, including anti-inflammatory, antimicrobial, and antidiabetic effects [82; 83]. In our results, the GF extracts contained various important flavonoids, such as naringin, quercetin, and hesperidin. Naringin, the main phenolic compound found in the GF peel extract, is a flavanone aglycone renowned for its multifaceted bioactive effects on human health. These effects include antioxidative, anti-inflammatory, antidiabetic, and anti-neurodegenerative properties, as reported in numerous studies [84; 85; 86].