## 4 Extraction of _Citrus_ Seed's Phytochemicals
### Traditional Extraction Methods
#### 4.2.4 High-Voltage Electric Discharge  
High-voltage electric discharge (HVED) is an application of liquid-phase discharge technology in which mechanical disruption of the cell wall is achieved by using water as a solvent. This extraction method follows two steps: a pre-breakdown phase and a breakdown phase. In the pre-breakdown phase, there is a corona streamer discharge, while the breakdown phase consists in an arc discharge process. Weak waves and small bubbles  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Matrix** & **Operational** & **Compounds** & **\%Yield** & **Activity** & **Ref.** \\ \hline \multirow{3}{*}{_Citrus reticulata_} & 50 \({}^{\circ}\)C, 33 MPa, 2 h & Esters, flavonoids, phenols, aldehydes, and triterpenes & & - & \\ \cline{2-6}  & & & 28.43/70.81/25.22/45.59 & Anticancer & \\ \hline \multirow{2}{*}{_Citrus limon_} & \multirow{2}{*}{40 \({}^{\circ}\)C, 300 bars, 8 h} & Fatty acids & 25.74/73.90/28.80/45.10 & - & \\ \cline{2-6}  & & (SFA/UFA/MUFA/PUFA) & 29.82/69.23/23.00/46.24 & - & \\ \hline \multirow{3}{*}{_Citrus aurantiglia_} & 60.85 \({}^{\circ}\)C, 48.5 MPa, 2 h, 10 g/min & & 11.64 & \multirow{3}{*}{Cytotoxic} & \multirow{3}{*}{[69]} \\ \cline{2-6}  & 54.85 \({}^{\circ}\)C, 43.5 MPa, 2 h, 10 g/min & & 11.72 & & \\ \hline \multirow{3}{*}{_Citrus limon_} & \multicolumn{4}{c}{_UAE_} & & \\ \cline{2-6}  & EtOH, 1 h, 50 \({}^{\circ}\)C, 200 W & & Flavonoids & & \\ \cline{2-6}  & & (epigallocatechin, caffeic acid, epicatechin, quercetin, and hesperidin) & - & - & [76] \\ \hline \multirow{3}{*}{_Citrus reticulata_} & MeOH, 30 min, 320 W 40 kHz, 320 W & Limonin & 0.11 & - & [77] \\ \hline \multirow{3}{*}{_Citrus bergamia_} & H\({}_{2}\)O, 1 h, 25 \({}^{\circ}\)C, 59 kHz & Limonin/Nomilin/TPC/TFC & 0.2/0.2/21.7/7.8 & Antioxidant & [79] \\ \hline \multirow{3}{*}{_Citrus sinensis_} & \multicolumn{4}{c}{_PLE_} & & \\ \cline{2-6}  & H\({}_{2}\)O, 180 \({}^{\circ}\)C, 10 min., 1002 kPa & Luteolin, diosmtein, & & \\ \cline{2-6}  & EtOH:H\({}_{2}\)O, 180 \({}^{\circ}\)C, 10 min., 1002 kPa & quercetin, 3-O-xyloside, & - & Antidiabetic & [80] \\ \cline{2-6}  & & and rutin & & \\ \hline \multirow{3}{*}{_Citrus bergamia_} & \multicolumn{4}{c}{_MAE_} & \\ \cline{2-6}  & EtOH:H\({}_{2}\)O (50\%), 800 W, 70 \({}^{\circ}\)C, 5 min & Limonin/Nomilin/TPC/TFC & 0.2/0.2/19.4/5.5. & Antioxidant & [79] \\ \hline \hline \end{tabular} Abbreviations: EAE: enzyme-assisted extraction; SFE-CO\({}_{2}\), supercritical fluid extraction using carbon dioxide; UAE: ultrasound-assisted extraction; PLE: pressurized liquid extraction; MAE microwave-assisted extraction; SFA: saturated fatty acids; UFA: unsaturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids.  
\end{table}
Table 3: _Cont._are generated. Moreover, there is a strong UV radiation formation and, consequently, active radicals appear [82]. Although there is no information about HVED applied in _Citrus_ seeds, it has been used for the extraction of lignin from rapeseed straws and oil from sesame seeds. In fact, a study run by [PERSON] et al. showed the positive effects of the arc treatment on the extraction of polyphenols from grape seeds [83]. HVED application for the _Citrus_ seed extraction should be studied to obtain further information.