From Waste to Beauty: Agri-Food By-Products as Sources of Antioxidant Compounds for Cosmeceutical Applications.

Agri-food processing generates large quantities of residues that are increasingly recognized as sustainable sources of bioactive ingredients for high-value applications. This narrative review examines agri-food by-products as sources of antioxidant compounds and provides an integrated mechanistic perspective on their applications in skin, oral, and hair care. By highlighting the shared antioxidant mechanisms of action underlying these applications, the review offers a comprehensive framework for understanding the cosmeceutical potential of agri-food-derived bioactive compounds. Peer-reviewed studies published mainly between 2015 and 2026 were considered, focusing on the chemical composition of by-products, green recovery strategies, biological mechanisms, and evidence from in vitro, ex vivo, in vivo, and clinical studies. Fruit and vegetable peels, seeds, skins, pomaces, and other agro-industrial residues contain polyphenols, flavonoids, phenolic acids, tannins, carotenoids, vitamins, lipids, peptides, and polysaccharides with antioxidant, anti-inflammatory, antimicrobial, photoprotective, anti-aging, moisturizing, and pigmentation-modulating properties. These compounds can reduce oxidative stress, support endogenous antioxidant defences, modulate redox-sensitive signaling pathways, attenuate inflammation, preserve extracellular matrix integrity, and improve skin barrier-related outcomes. Green extraction technologies, including ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, pressurized liquid extraction, and natural deep eutectic solvents, enhance their sustainable recovery. Overall, agri-food by-products represent promising resources for circular cosmeceutical innovation, although extract standardization, safety, stability, skin bioavailability, formulation performance, and controlled clinical validation remain essential for translation.