# Emerging Trends in Sustainable Biological Resources and Bioeconomy for Food Production
## 5 Common Resources in Green and Blue Bioeconomy
### Natural Polypphenols and Antioxidants
Nowadays, researchers and industries alike have turned their attention to alternative and underutilized matrices, particularly those aligned with sustainability goals. In this context, agro-industrial by-products (fruit peels, seeds, pomace, and other processing residues) have emerged as promising raw materials rich in phenolic compounds [89]. These by-products often contain significant amounts of polyphenols, polysaccharides, organic acids, and other functional molecules, making them economically attractive and environmentally responsible options for ingredient development [79]. Residues from grape, apple, and pomegranate processing are rich in high-value phenolics such as anthocyanins and tannins [90,91]. Avocado peels contain important amounts of procyanidins, catechin, and phenolic acids [92]. Grape pomace, for example, retains about 70% of the polyphenols present in grapes and has shown strong antioxidant and antimicrobial activity [93]. Similarly, spent coffee grounds and palm oil effluents have emerged as viable sources of antioxidants when processed appropriately [94,95]. Other non-conventional sources include edible mushrooms, macroalgae [96], edible flowers [97], and dandelion seeds [98], which untapped polyphenic profiles. The efficient extraction of phenolic compounds from plant matrices is of crucial importance for their application in the food and health sectors. Conventional extraction methodologies, encompassing maceration, Soxhlet extraction and reflux, have been extensively utilized. Nevertheless, these techniques are frequently subject to criticism due to their extended processing times, substantial energy demands, and reliance on hazardous solvents [77]. These limitations have prompted the development of greener and more efficient extraction techniques that aim to increase extraction yield while minimizing environmental impact. Among emerging technologies, ultrasound-assisted extraction (UAE) has proven effective due to its ability to enhance mass transfer through cavitation, reducing both extraction time and solvent usage [79]. Microwave-assisted extraction (MAE) has been demonstrated to accelerate the rupture of cell walls and the solubilization of target compounds, thus offering a high yield in a reduced time frame [77]. Supercritical fluid extraction (SFE), particularly employing CO\({}_{2}\), is optimal for thermosensitive compounds and yields solvent-free extracts. The methodology has been successfully applied to matrices such as dandelion seeds and garlic [98,99]. Another promising method is the use of natural deep eutectic solvents (NADES), which are biodegradable and capable of solubilizing a wide range of phenolics due to their strong hydrogen-bonding networks [94]. Enzyme-assisted extraction (EAE) has been shown to be a particularly effective method for the breakdown of plant cell walls, with the purpose of releasing bound phenolics, particularly in fruit and vegetable by-products [93]. These innovative extraction technologies are in alignment with sustainability principles and allow for the valorization of food industry waste streams. When integrated with scalable industrial processes, they offer an environmentally friendly and economically viable route to producing high-quality phenolic-rich extracts for nutraceutical and functional food applications [89,100]. Notwithstanding the advantages inherent in phenolic compounds, their bioavailability is influenced by a multitude of factors, including chemical structure, molecular size, release in the food matrix, conjugation with other compounds, degree of polymerization, solubility, metabolism, and intestinal absorption [82,84]. In order to capitalize on the full therapeutic potential of phenolic compounds in the prevention and management of chronic diseases, it is essential to enhance their bioavailability. In order to address these challenges, a number of strategies have been developed. * Chemical modification, encompassing a range of reactions such as methylation and glycosylation, is a fundamental aspect of biological research.