Molecular remodeling of waste-derived polyphenols: engineering tea and grape by-products into high-value functional molecules

The tea and wine industries generate millions of tonnes of polyphenol-rich residues annually, yet conventional valorization relies on solvent extraction of native molecules, inheriting instability and poor bioavailability. We argue that molecular remodeling—applying enzymatic, microbial, chemical, and supramolecular tools to redesign waste-derived polyphenols—is a more productive frame. We organize the literature through a Liberation–Remodeling–Validation framework linking three pathways: oxidative upcycling of catechins to benzotropolone dimers and anthocyanins to polymeric pigments; structural derivatization through acylation, pyranoanthocyanin formation, and depolymerization; and intermolecular assembly via copigmentation and protein–pigment complexes. Natural deep eutectic solvents emerge as green media to liberate, solubilize, and stabilize remodeled products. We contend that molecular remodeling, rather than extraction, unlocks the functional potential of tea and grape by-products, shifting priority from purified-substrate proofs-of-concept to real waste matrices. In vivo toxicology, dose–response validation, and regulatory frameworks for these chemically distinct entities remain largely undeveloped and must be addressed before industrial translation.