Extraction of Bioactive Compounds from Cocoa Pod Husk ( <i>Theobroma cacao L.</i> ) Using Deep Eutectic Solvent Assisted with Ultrasound

Introduction: The cocoa pod husk (CPH), as a waste of the chocolate industry, is a potential source of bioactive compounds. Objective: This study aimed to evaluate the bioactive compounds in CPH and to optimize their extraction process using Deep Eutectic Solvents (DES) assisted by ultrasound (UAE-DES). Methods: CPH from Southern Vietnam was subjected to UAE-DES extraction. The optimal parameters were investigated, including ultrasonic time (20-60 min), ultrasonic temperatures (40-60 °C), and substrate-to-solvent ratio (1:5-1:20 which is equivalent to 20%-5% based on the weight of substrate). Phenolic compounds were analyzed using the UHPLC-DAD-MSQ system, and total polyphenol content (TPC), total flavonoid content (TFC), and catechin concentration (CC) were measured using spectrophotometric methods. The antioxidant capacity was assessed using ABTS, DPPH, and FRAP methods. Results: The optimal extraction conditions were found to be at 50 °C for 40 min using ultrasound technology, with a substrate-to-solvent ratio of 1:20 (5%). The total phenolic (TPC), total flavonoid (TFC), and catechin content (CC) of the obtained extract at these conditions were approximately 10.14 gGAE/100 g dry weight of substrate, 2.18 gGE/100 g dry weight of substrate and 64.80 gCE/100 g dry weight of substrate, respectively while their antioxidant capacity was 13.725 g TE/100 g dry weight of substrate, 67.1% OR (DPPH inhibition) and 0.887 gFeSO4/100 g dry weight of substrate assayed using ABTS, DPPH and FRAP methods, respectively. The quantitative analysis indicated a complex mixture including hydroxycinnamates, flavones, flavan-3-ols, and anthocyanidins in extracted CPH. Conclusion: These findings indicated that CPH is a potential source of bioactive compounds. The optimal extraction process of UAE-DES can maximize the polyphenolic content while achieving high antioxidant capacity.