Sustainable Valorization of Cocoa Bean Shells: Efficient Extraction of Phenolic Compounds and Methylxanthines

Abstract Cocoa bean shell (CBS), a major by-product of the cocoa industry, presents an underutilized opportunity for bioactive compound (BC) recovery contributing to sustainable waste valorization. This study investigates the extraction of phenolic compounds and methylxanthines (theobromine and caffeine) from CBS using green solvents and three extraction techniques: mechanical stirring extraction (MSE), microwave-assisted extraction (MAE), and ultrasound-assisted extraction (UAE). The effects of ethanol concentration, extraction time, and temperature were systematically evaluated to optimize the extraction efficiency. High-performance liquid chromatography (HPLC) and spectrophotometric analyses were used to quantify key bioactive compounds and assess antioxidant activity. The results indicated ethanol/water 50:50 ( v/v ) was the most efficient solvent. MSE at 50 °C for 30 min yielded the highest recovery of polyphenols and methylxanthines and demonstrated the best balance of yield, energy efficiency, and scalability, making it the most promising approach for industrial applications. LC–MS/MS analysis further confirmed the presence of key phenolics, including epicatechin, catechin, and procyanidins. This study provides a novel comparative assessment of three green extraction techniques and identifies the most scalable and industrially viable approach for the sustainable valorization of cocoa bean shells, thereby underscoring the potential of CBS as a valuable source of bioactive compounds and supporting its integration within circular economy frameworks for food, pharmaceutical, and nutraceutical applications. Graphical abstract