Natural deep eutectic liquids as green solvents in intensified extraction of bioactive compounds from fruit wastes

Plant waste, such as fruit and vegetable waste, has become a striking environmental, economic, as well as food safety issue. Fruit wastes, for example, fruit peel, pomace, skin, rag, and seed fragment, act as feedstock for extracting numerous bioactive compounds, that is, phenolics, pectin, lipids, etc. These bioactive compounds show antioxidant activity which is primarily beneficial for reducing health issues in humans (e.g., alzheimer, cancer, diabetes, etc). Conventional extraction methods for extracting bioactive compounds suffer from large energy consumption, greater solvent usage, and reduced quality/quantity of bioactive compounds, all of which necessitate a shift toward non-conventional methods. This review article discusses the green solvent extraction methods, especially focusing on intensified extraction using deep eutectic solvents (DES) and natural deep eutectic solvents (NADES). In this article, a thorough analysis of the extraction through both conventional and non-conventional techniques is conducted. Subsequently, this article provides a systematic overview with the detailed description of the fruit waste scenario, green solvents, extraction mechanisms, factors influencing the extraction, and adaptation of new techniques for enhancing the extraction efficiency. Review suggests that ultrasound-microwave assisted extraction with natural deep eutectic solvents (UMAE-NADES) technique results in reduced extraction time (about 12–60 times) with respect to conventional method while improving the extraction (about 50%) with moderate conditions.