Selective fixed-bed fractionation of stilbene subfamilies from grape cane waste using a pyridine-amide adsorbent

The selective separation of structurally analogous polyphenols from complex plant matrices remains a longstanding challenge in bioseparation engineering. This study introduces a custom-designed adsorbent, poly(2,6-bis(acrylamido)pyridine) (poly(BAAPy)), tailored for subfamily-level resolution of stilbenes obtained from crude grape cane extracts. Leveraging dual amide and pyridine functionalities, poly(BAAPy) achieves selective retention of oligomeric stilbenes (e.g., trans-ε-viniferin, miyabenol C) via multivalent hydrogen bonding and π-π stacking interactions. Comparative breakthrough experiments against commercial poly(4-vinylpyridine) (poly(4VP)) demonstrate superior oligomer retention across both ethanol-water and acetonitrile systems. In dynamic closed-loop adsorption mode, poly(BAAPy) enabled polarity-driven elution and achieved up to a 3.4-fold enrichment of stilbene oligomers, with their recovery in fractions containing ≥ 90% oligomeric content in a single desorption cycle. Uptake profiles and adsorption selectivity coefficients confirmed poly(BAAPy)’s preference for oligomers under both ethanol-water and acetonitrile conditions. The total stilbene recovery was 75%. Breakthrough data were fitted using both empirical (Clark, Thomas) and mechanistic models, revealing distinct adsorption dynamics for poly(BAAPy) versus a commercial poly(4VP) resin. This work demonstrates a sustainable valorisation route for grape cane waste, converting viticultural residues into a high-value source of bioactive compounds. The use of green solvents and fixed-bed adsorption aligns with circular economy principles and environmentally conscious separation processes.