# Red Orange and Bitter Orange IntegroPectin: Structure and Main Functional Compounds
## 3 Results and Discussion
### Biophenols  
Table 3 lists the flavonoid and other phenolic compounds found using the highly sensitive HPLC-MS technique employed in red orange IntegroPectin, bitter orange IntegroPectin, and bitter orange IntegroPectin re-extracted at 90 \({}^{\circ}\)C.  
Results in Table 3 clearly show the abundance of phenolic compounds in both orange IntegroPectin samples, with a uniquely high concentration found in bitter orange IntegroPectin, amounting to 119.60 mg/g, namely nearly seven times higher than the amount found in red orange IntegroPectin. Furthermore, it is enough to treat the bitter orange IntegroPectin extracted with aqueous EtOH with another aliquot of the same solvent at higher temperature (90 \({}^{\circ}\)C), to extract another significant amount (19.22 g/kg) of biophenols. Hesperidin (hesperetin 7-rutinoside), naringin (4',5,7-trihydroxyflavonone-7-rhamnoglucoside), and eriocitrin (eriodictyol 7-rutinoside) are, by far, the most abundant compounds found in the bitter orange pectin. Hesperidin and naringin are the two main flavonoids found in the red orange pectin samples. Remarkably, and pointing to the well-known poor solubility of hesperidin and naringin in protic solvents [27], a significant amount of the latter flavanone glycosides can be extracted at 90 \({}^{\circ}\)C from the bitter orange pectin sample already extracted at room temperature. Diosomin (diosment 7-O-rutinoside) was only detected (0.285 mg/g) in the bitter orange pectin extract, whereas nruit (quercetin-3-O-rutinoside) was found (0.131 mg/g) only in the red orange pectin sample. From a compositional viewpoint, these results are in agreement with previous findings for which bitter oranges possess a unique flavanone profile dominated by naringin, neoeriocitrin, and neohesperidin, with a total flavanone aglycones amount of about 48 mg/100 g fruit, significantly higher than that of sweet oranges (about 17 mg total flavanone aglycones/100 g) [28]. However, the amount of flavanone found at the surface of both citrus IntegroPectin samples is three orders of magnitude higher in the case of the IntegroPectin samples than in the fruit peel. This, once again, is due to the adsorption and concentration process taking place during the HC-based extraction process followed by freeze-drying of the aqueous extract rich in flavonoids released into the aqueous phase most likely with pectin acting as emulsifying agent. For comparison, the overall amount of biophenols found in grapfruit IntegroPectin, a powerful and broad-scope antibacterial \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Compound Class**} & **Red Orange** & **Bitter Orange** & **Bitter Orange** \\  & **IntegroPectin** & **IntegroPectin** \\  & **(mg/g)** & **(mg/g)** & **Re-Extracted at 90 \({}^{\circ}\)C** \\ \hline \multicolumn{3}{c}{**Flavonoids**} \\ \hline Rutin & 0.131 & - & - \\ \hline Naringin & 2.004 & 47.164 & 9.494 \\ \hline Naringenin & - & 0.169 & - \\ \hline Hesperidin & 15.087 & 56.811 & 7.961 \\ \hline Hesperetin & - & 0.173 & - \\ \hline Eriocitrin & - & 14.765 & 1.690 \\ \hline Diosmin & - & 0.286 & 0.055 \\ \hline \multicolumn{3}{c}{**Phenolic acids**} \\ \hline Caffeic acid & - & 0.236 & 0.016 \\ \hline Gallic acid & 0.015 & - & - \\ \hline
**Biophenols (total)** & 17.24 & 119.60 & 19.22 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Phenolic compounds in red orange IntegroPectin, bitter orange IntegroPectin, and bitter orange IntegroPectin re-extracted at 90 \({}^{\circ}\)C.  
agent [6], was about 75 mg/g [29]. The high amount of naringin (47.16 mg/g), about half of that found in grapefruit IntegroPectin (73.66 mg/g), imparts the bitter taste to C. _aurantium_ due to the sugar neohesperidose, in contrast to rutinose of hesperidin that causes these flavonones to have a neutral taste [30]. Remarkably, the amount of eriocitrin found in _C. aurantium_ IntegroPectin (14.76 mg/g) is nearly five times higher than in lemon IntegroPectin (3.35 mg/g) [29].