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This study aims to produce a biodegradable active packaging film that is pH sensitive, and has a good antioxidant and antimicrobial activity. To do this, a novel phenolic extract was interfacially assembled onto a cellulose film, resulting in a film with a pH-triggered release mechanism of the active polyphenol agent. First, an aqueous extraction of cashew nut testa (CTE) was performed and subsequently, the CTE was characterized. The disc diffusion assay showed that CTE exhibited antimicrobial activity towards the food pathogens Escherichia coli (6 mm) and Staphylcoccus aureus (12 mm). CTE was also cytotoxic against cancer HepG2 and HEK293 cells, reducing the viability to 52% and 47%, respectively. It was incorporated into a cellulose-based packaging film, prepared from the by-product, sugarcane bagasse (SC) through interfacial assembly. The incorporation of CTE resulted in a film with good antimicrobial activity, excellent antioxidant content (91%), and has extremely high thermal stability (290 °C). FTIR indicated the formation of hydrogen bond between the SC cellulose-based film and CTE. The hydrogen bonds formed between the cellulose film and CTE became the driving force behind the pH-triggered release mechanism. It was found that the active agent, tannic acid, could be controllably released from the film, depending on the pH of the environment. Our strategy to produce a cellulose-based film impregnated with a phenolic extract, using interfacial assembly, resulted in an active packaging film with pH-triggered release mechanism. This film could be useful to extend the shelf life of perishable food items. [ABSTRACT FROM AUTHOR]