###### Abstract  
Increasing research is being directed toward the production of value-added products using plant extracts that are super-fortified with antioxidants. In this study, the extraction parameters for bioactive compounds (such as polyphenols) from _Nasturtium officinal_ leaves and their antioxidant properties were optimized using response surface methodology. The optimization procedure examined the effects of the extraction temperature, time, and solvent composition on conventional magnetic stirring (ST). In addition, the impacts of two green techniques--pulsed electric field (PEF) and ultrasound (US)--were evaluated individually and in combination to assess their potential to enhance the extraction of the compounds. According to our findings, under the proposed extraction conditions (a combination of PEF, US, and ST as a extraction technique, 50% ethanolic solvent, for 30 min at 80 \({}^{\circ}\)C). _N. officinal_ leaf extract proved to be an excellent source of bioactive compounds, with extracts containing rosmarinic acid (3.42 mg/g dried weight (dw)), chlorogenic acid (3.13 mg/g dw), total polyphenol content (28.82 mg of gallic acid equivalents (GAE)/g dw), and strong antioxidant properties. The FRAP method measured 57.15 umol ascorbic acid equivalents (AAE)/g dw, while the DPPH radical scavenging activity method measured 47.55 umol AAE/g dw. This study was carried out to evaluate and improve the concentration of bioactive compounds in _N. officinal_ leaf extract, resulting in a product with multiple applications across the food, cosmetic, and pharmaceutical industries. w watercress; green extraction techniques; pulsed electric field; ultrasound; polyphenols; rosmarinic acid; antioxidants +
Footnote †: journal: applied sciences  
0000-0001-9993-3399/00/0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-00  
a low amount has been documented; in the vegetative period, the amount ranges between 8.03 and 9.35 mg gallic acid equivalents (GAE)/g, and in the generative period, the quantity is lower (between 6.5 and 7.65 mg GAE/g) [2]. Polyphenols, found in abundance in plants, have become an emerging field of interest in nutrition in recent decades since a rising body of research shows that polyphenol consumption plays a vital role in human health [7]. The solid-liquid method is one of the classical and conventional extraction techniques for the recovery of polyphenols [8]. This extraction method is based on the performance of different solvents or hot water extraction [9]. However, it also has some limitations, such as low efficiency and long extraction time, high solvent cost, and degradation of volatile compounds. Therefore, it is not considered \"green\" and attractive, and for this reason, some of the conventional solid-liquid extraction processes are well suited to be supported by green methods, such as ultrasound, to disrupt the cell wall structure of plant raw materials [8]. Nowadays, studies are being carried out to isolate the maximum amount of polyphenols from plant products using mainly green extraction methods [10; 11; 12]. A green extraction method or technique is an extraction process that has low energy consumption, a short extraction duration, and/or uses new-generation, non-harmful solvents, and ensures a safe and high-quality final product [13; 14; 15]. Among the green extraction methods, pulsed electric field (PEF), ultrasound (US), supercritical fluid extraction (SFE), pressurized liquid extraction (PLE), and microwave-assisted extraction (MAE) are the most renowned [16]. The advanced technologies of MAE, US, and PEF provide the basis for a significantly reduced cost of production of enhanced extracts [10]. Although the PEF system is an advanced extraction method, it has limitations in the food industry, such as the occurrence of electrochemical reactions at the electrode-rotor interface. These reactions can lead to significant alterations, such as electrolysis of water and chemical changes in the food product [17].