Phytochemical Characterization and Antioxidant/Antitumoral Potential of Coffee Silverskin: Comparative Insights with Green and Roasted Coffee.

Coffee is one of the most consumed beverages worldwide, and epidemiological studies suggest it may reduce the incidence of certain cancers. However, the anticancer potential of coffee silverskin (CS), the main by-product of coffee roasting, remains unexplored. This work aimed to valorize this bioresource by characterizing its bioactive composition and assessing its antioxidant and antitumoral potential. CS aqueous extracts were obtained through a fast and eco-friendly ultrasound-assisted extraction method and analyzed regarding caffeine, 5-caffeoylquinic acid, and amino acids (total and free). Their effects on cell growth, proliferation, viability, migration, lipid peroxidation, angiogenic factors, and cell cycle distribution were evaluated in pancreatic, breast, and colorectal cancer cell lines. Results were compared with those of green coffee (GC) and roasted coffee (RC) extracts. Despite presenting lower amounts of the bioactive compounds analyzed than GC and RC, CS extract exhibited a marked anticancer potential, surpassing the effects of GC and RC extracts in most assays. These findings position CS as a sustainable and high-value source of bioactive compounds with antitumoral potential, supporting biowaste valorization, circular economy, and sustainable production while contributing to health and well-being goals aligned with United Nations SDGs 12 and 3. Further studies are needed to clarify its mechanisms and in vivo efficacy.