Accelerated Solvent Extraction as an Alternative for the Recovery of Phenolic Compounds from Chestnut Bur: Optimization of Extraction Conditions

Chestnut bur (CB) is a solid waste product generated in large quantities during the harvesting of edible fruits. This by-product is rich in total phenolic content (TPC) with high antioxidant properties, making it suitable for use in a variety of industrial applications. In this study, the operational variables of accelerated solvent extraction (ASE) and conventional solvent extraction (CSE) of CB were optimized in order to obtain extracts with maximum levels of TPC. The analysis revealed that the extract obtained by ASE using 31.3% ethanol at 180 °C for 9 min achieved the highest value of TPC (8.37 ± 0.05 g gallic acid equivalents (GAE)/100 g dry matter (DM)). Moreover, this extract exhibited higher values of radical-scavenging activity for α,α-diphenyl-β-picrylhydrazyl (DPPH) (90.8 ± 0.3%) than those observed for catechin standard (88.7 ± 0.2%). In addition, its phenolic composition revealed high amounts of gallic acid (13.22 ± 1.01 mg/g DM), followed by 3,4-dihydroxybenzoic acid (2.96 ± 0.16 mg/g DM). This study demonstrates the potential for valorization of CB by ASE under feasible extraction conditions, thereby promoting the circular economy.