From Agri-Food Byproducts to High-Value Bioactive Compounds: A Critical Review Linking Green Recovery and Chemical Profiling to Circular Valorization

Agri-food byproducts are increasingly recognized as sustainable feedstocks for high-value bioactive compounds, but their practical valorization requires integrated evidence on recovery conditions, chemical composition, bioactivity, and application readiness. This review critically examines green recovery strategies and chemical profiling platforms for bioactive compounds recovered from peels, pomace, seed residues, hulls, vegetation waters, and pruning waste. Emphasis is placed on how extraction variables shape chemical profiles, extract quality, and reported biological activities. Ultrasound- and microwave-assisted extraction, enzyme- and fermentation-assisted recovery, supercritical fluid extraction, pressurized liquid extraction, pulsed electric field-assisted pretreatment, and green solvent-based extraction are discussed in terms of target-compound selectivity, solvent and energy demand, process safety, scalability, and sustainability-related evidence. Chromatographic, mass-spectrometric, spectroscopic, and metabolomics-based profiling approaches are evaluated for identification, annotation, quantification, fingerprinting, quality-marker selection, and standardization, with confidence levels distinguished according to authentic-standard matching, tandem mass spectrometry evidence, spectral libraries, or fingerprint-level evidence. Circular valorization pathways in food, nutraceutical, cosmetic, pharmaceutical-oriented, and biopesticide-related applications are further considered with attention to feedstock heterogeneity, process standardization, stability, safety, regulatory feasibility, scalability, and techno-economic feasibility. Overall, this review provides a linkage-oriented framework for developing standardized, application-readiness-oriented bioactive candidates from agri-food byproducts.