Extracting bioactive compounds from fruit peel waste: Techniques for extraction, purification, characterization, and applications.
Global fruit production reached 953.8 million tonnes in 2024, generating peel residues of 15%-50% of fruit weight that are largely discarded despite containing polyphenols, carotenoids, dietary fiber, and enzymes of commercial value. Existing reviews address this in fragments, covering extraction, green solvents, or food applications alone, but none traces the full pipeline from raw peel to finished product. This review provides an integrated, critically evaluated assessment of the entire valorization chain: extraction, purification, characterization, biological evaluation, and application. Rather than cataloguing methods, we compare them against yield, solvent use, energy demand, environmental impact, and scalability. Ultrasound- and microwave-assisted extraction cut processing time by 70%-95% and solvent use by 50%-90%, while supercritical CO2 extraction offers selectivity for non-polar compounds at high cost. Purification is the least standardized step, with resin adsorption and membrane separation most scalable. Characterization suffers from inconsistent validation, with detection limits, recovery, and matrix effects often unreported. Peel bioactives act through defined pathways (NF-κB, PI3K/AKT/mTOR, apoptosis, Nrf2, AMPK/GLUT4), yet efficacy is often shown at concentrations exceeding achievable plasma levels, making bioavailability the principal translational barrier. This review will be valuable to researchers in food science, analytical chemistry, and pharmaceutical sciences by integrating these traditionally different stages and identifying the key challenges that limit industrial and clinical translation.