Natural polyphenol-modified cellulose: Adsorption, antibacterial activity, and release behavior

Naturally occurring polyphenols offer a sustainable alternative for functionalizing cellulose-based materials with antibacterial properties. In this study, selected flavonoids (quercetin, myricetin, baicalein) and stilbenes (resveratrol, piceatannol) were employed as model compounds to investigate their adsorption, desorption, and antibacterial performance when immobilized on cellulose paper via physical adsorption. Raman spectroscopy confirmed successful adsorption of all polyphenolic compounds onto the cellulose surface. Antibacterial activity against Staphylococcus aureus ( S. aureus ) and Escherichia coli ( E. coli ) was evaluated using both disk diffusion and agar well diffusion assays, revealing pronounced assay-dependent behavior, with the disk diffusion assay showing false antibacterial results. In contrast, agar well diffusion assay showed antibacterial activity against S. aureus for all compounds, while myricetin and piceatannol showed higher efficacy against E. coli . Desorption studies revealed that stilbenes (resveratrol and piceatannol) were released more readily from the cellulose surface, whereas flavonoids (quercetin, myricetin, baicalein) remained largely bound, reflecting differences in molecular structures and hydrogen-bonding capacity. These results establish a structure–desorption–activity relationship that explains discrepancies commonly reported for polyphenol-based antibacterial cellulose materials and provides mechanistic guidance for the design of cellulose-based surfaces with tunable antibacterial performance.