# Portuguese Grapevine Leaves: A Neglected By-Product with High Potential
## 3 How Can Portuguese Grapevine Leaves Contribute to Meeting the Goals of the 2023 Agenda?
Green extraction methods, namely pulsed electric field (PEF)-assisted extraction, and pressurized liquid- (PLE), microwave- (MAE), and ultrasound-assisted extraction (UAE), among others, are effective technologies that can help achieve 2030 goals and meet the demands of both consumers and industries [14] while preserving food safety and recovering bio-compounds from by-products [8; 179]. Da Rocha and Norena (2020) [180] extracted phenolic compounds from grape pomace using UAE and MAE, but the total phenolic content separated by these green techniques, as well as the corresponding antioxidant activities, were higher when using a conventional procedure. However, according to Dahmoune et al. (2014) [181], MAE of Pistacia lenticus L. leaves allowed a higher extraction yield compared to UAE or conventional methods, resulting in extracts with higher concentrations of total phenolics, flavonoids, and tannins, as well as greater antioxidant activity. These findings are consistent with Hayta and Iscimen (2018) [182], who demonstrated that both MAE and UAE allowed efficient extraction of bioactive compounds from plant materials. Bubalo et al. (2016) [183] also utilized green extraction procedures, associated with the use of deep eutectic solvents, to extract phenolic compounds from grape skins, and found that UAE was the most efficient method compared to MAE and conventional extraction. MAE can be optimized by adjusting factors such as solvent choice, extraction time, sample size, power density, and liquid/solid ratio. UAE yield depends on solvent, extraction time, frequency of the ultrasound, swelling rate, disruption, and particle size [14; 184]. PEF-assisted extraction can be optimized by modifying parameters like electric field intensity, energy input, solvent, extraction temperature, and diffusion time. Carpentieri et al. (2023) [185], used this technology to extract efficiently phytochemical compounds from grape pomace, including phenolics, flavonoids, anthocyanins, as well as tannins, such as epicatechin, p-coumaric acid, chlorogenic acid, gallic acid, and peonidin 3-O-glucose. The PEF extraction yield of these bio-compounds was higher compared to those obtained using conventional methods, which was attributed to a greater level of permeabilization of the by-product tissue cell membrane. Pressurized liquid extraction (PLE) is another technique developed in recent years, and stands out for being faster and requiring less solvent than conventional methods, while achieving better yields. It uses green solvents, such as water and natural deep eutectic solvents, and automates the extraction process (Machado et al., 2024) [176]. According to these authors, the newest updates of PLE, such as accelerated solvent extraction (ASE), can be used efficiently to extract phenolic compounds from grape pomace, in conformity with Silva et al. (2024) [186], who also extracted anthocyanins from the same by-product. The encapsulation of grape by-product extracts can produce solid products, which have the advantage of being more stable and taking up less space, which translates into lower costs in terms of packaging, storage, and transportation [186], in line with the goals of the 2030 Agenda. Thus, the bioactive compounds present in grapevine leaves, once efficiently extracted using green techniques that require smaller solvent volumes and reduced extraction times [184], have the potential to be incorporated into food, pharmaceuticals, and cosmetic formulations. Potential Utilization and Good Practices for Grapevine Leaves in Various IndustriesGrapevine leaves, long considered an underutilized by-product of the wine industry, are gaining recognition for their valuable bioactive compounds, with potential applications across multiple sectors, including food, pharmaceuticals, nutraceuticalals, cosmetics, and agriculture.