Exploration of cosmetic bioactive compounds from cocoa bean shell using polyol-based microwave-assisted extraction: Cytotoxicity, anti-tyrosinase, and anti-melanogenesis properties

Cocoa bean shells, a major byproduct of the cocoa industry, hold significant potential for value-added applications, particularly in cosmetics. The aim of this study was to develop a sustainable, eco-friendly extraction process for bioactive compounds with skin-whitening properties using microwave-assisted extraction (MAE) and polyol-based solvents, a novel approach in cocoa bean shell valorization. Polyols, such as propylene glycol (PG), were compared to ethanol (EtOH) for their efficiency in extracting bioactive compounds. The influence of polyol type, polyol concentration, solid-to-liquid ratio, temperature, and extraction time on total phenolic content (TPC), total flavonoid content (TFC), and tyrosinase inhibitory activity was systematically evaluated. This study demonstrated that PG, at optimal conditions (60 % w/v, 1:50 solid-to-liquid ratio, 100 °C, 30-min extraction), significantly enhanced TPC (59.57 ± 1.33 mg GAE/g sample), TFC (242.24 ± 2.95 mg QE/g sample), and tyrosinase inhibition (4.75 ± 0.35 mg KAE/g sample) compared to EtOH. LC-QQQ analysis identified quercetin, catechin, and trigonelline as key contributors to tyrosinase inhibition and melanin content reduction, with PG extracts demonstrating superior functional activity despite similar quercetin levels in both solvents. Comparative cytotoxicity, anti-melanogenic assays, and cellular tyrosinase inhibition further confirmed the enhanced safety and efficacy of PG extracts over conventional ethanol extracts, positioning them as a novel green solvent system for developing effective skin-whitening active ingredients in cosmetic formulations.