Green Extraction of Coffee Silverskin Bioactives Using Deep Eutectic Solvents and Their Cosmetic Application

The huge amount of waste from the coffee industry should be valorized since it is a potential antioxidant source. Deep eutectic solvents (DESs) have emerged as promising and environmentally benign alternatives to conventional organic solvents for the recovery. In this study, 18 different DES systems prepared from glycerol and various hydrogen bond donors (HBD) components were evaluated. The glycerol-maltose (Gly-Mal) (2:1, molar ratio) combination providing the highest efficiency regarding total phenolic content (TPC) was determined. Homogenizer-assisted extraction method (HAE) was applied with this selected DES. Extraction conditions were optimized with a Box-Behnken experimental design depending on three parameters. The highest TPC (48.10 mg GAE/g DM) and DPPH inhibition (42.31%) values were obtained under the conditions of 0.1 g biomass, 30% water (v/v), and 55 s time. The best extract was added to three moisturizing cosmetic products. The oxidative stability, total phenolic substance amount, and antioxidant activity in the formulations with the DES-based extract were significantly increased. These improvements were further validated by principal component analysis (PCA). This study presents a multidisciplinary approach for the conversion of biowaste into high-value ingredients by combining solvent design, statistical optimization, and cosmetic product application.