Valorization of Coconut By-Products Using Eutectic Solvents: A Comprehensive Review on Green Extraction

Coconut (Cocos nucifera L.) is one of the most widely cultivated tropical crops, generating substantial by-products during industrial processing. Although rich in lignocellulosic components, phenolic compounds, lipids, and other bioactive molecules, they are often discarded or burned as low-grade fuel, causing environmental pollution and the proliferation of disease-carrying vectors. The sustainable valorization of these by-products is therefore essential to reduce environmental impact and enhance the economic value of the coconut chain. In this context, eutectic solvents (ES) have emerged as powerful potential green alternatives to conventional organic solvents for the extraction and fractionation of biomolecules. ES are formed through hydrogen-bonding interactions between hydrogen-bond donors and acceptors, yielding tunable solvents with low volatility, high selectivity, and biocompatibility. Their application to coconut biomass can enable the recovery of high-value compounds such as lignin, tannins, phenolic compounds, and fatty acids. This review provides a comprehensive overview of ES-based strategies for coconut by-product valorization, highlighting solvent compositions, main by-products explored, and target compounds extracted. Furthermore, it compares ES efficiency with traditional techniques and identifies current research gaps. Finally, the review highlights challenges and future directions for expanding ES application toward full coconut utilization, emphasizing their critical role in advancing sustainable, green chemistry.