# Advanced and Potential Methods for Extraction of Bioactive Compounds from Avocado Peel--A Review
## 4 Advanced Methods for Extraction of Bioactive Compounds from Avocado Peel
### Ultrasound-Assisted Extraction (UAE)  
Ultrasound-assisted extraction (UAE) is one of the most straightforward extraction techniques and an efficient method to extract metabolites from plants in shorter times than other extraction methods [17; 18]. The main reasons why UAE is a favored extraction technique for extracting active compounds are its adaptability and the possibility of using less or no organic solvent, its nature as a physical extraction technique, its simplicity of operation, its extraction effectiveness, its capacity to preserve the biological activity of extracted substances, its reduced reliance on time, and its industrial application, among other things [19; 20]. The type of plant material, extraction solvent, and micro-environmental extraction factors significantly impacted UAE outcomes. This means that the extraction technique must be optimized for each plant material and ultrasonic equipment employed to provide the optimum outcomes regarding extraction yields and biological activity preservation. In the study of [PERSON] et al. [21], UAE was used to retrieve phenols from avocado peel. It was reported that the major polyphenic compounds identified in the extracts were benzoic acid, vanillic acid, resveratrol, and syringe acid. The most effective conditions for recovering phenols from the avocado peel were reported to be a solid-to-solvent ratio of 1:20 (\(w/v\)), ultrasonic intensity of 20%, and duration of 30 min. This study concluded that the UAE was more efficient than enzyme-assisted extraction. As was well-stressed in the study of [PERSON] et al. [22], the application of UAE resulted in avocado peel extract containing phenolic and flavonoid compounds, which presents high antioxidant activity and low cellular toxicity in normal cells, indicating that avocado peel extract is safe for human consumption. UAE has been proven to retrieve bioactive compounds from avocado peel successfully. However, more studies are necessary to comprehend the effect of UAE on the extract composition and to understand the structure and functional changes before and after the extraction processes by comparing them with the controls. This can aid in determining the impact of chemicals on degradation and the amounts of certain compounds in extracts. In addition, to determine the process's safety for usage in foods and other applications, researchers must investigate the degradative effects of UAE on bioactive compounds and their intermediary products, as well as their biological impacts in vitro and in vivo. In this context, ion-based liquid, also called ion-based liquid ultrasound-assisted extraction (ILUAE), is now an emerging extraction technology that could replace conventional solvents in the UAE. In recent years, IL-based extraction strategies have been employed to extract phenolic chemicals from plant sources [23; 24]. Ionic liquids (ILs) are simple molten salts that are liquid at or near room temperature and include a relatively significant organic cation and an inorganic anion. Ionic liquids provide potential advantages over ordinary organic solutions, such as a low melting point, a vast liquid temperature range, low vapor pressure, and extended, specialized solvent characteristics [25]. One of the advantages of this technology is the ability to optimize their properties for a specific application by changing the nature of the anion/cation pair; also, the speed of reactions, selectivity, and yield are frequently more incredible in ionic liquids. The non-volatility of ionic liquids is employed in many chemical processes because it prevents operators from being exposed to solvent vapors. At ambient temperatures, ionic liquids have no vapor pressure and are thus non-volatile, eliminating the hazards and pollution of solvent evaporation. Salts dissolve well in ionic liquids and are miscible with other solvents. The organic reaction product can be removed easily from the ionic liquids containing the catalysts. As a result, the catalyst can be extracted from the products and reused.