Grumixama Phenolic Extract-Loaded Alginate–Chitosan Films for Wound Dressing Applications: Effect of Secondary Crosslinking Time on Mechanical Properties[

Grumixama (Eugenia brasiliensis Lam.) is an underutilized Brazilian fruit rich in bioactive compounds, representing a promising source of phenolic compounds for the development of functional biomaterials. This study investigated the ultrasound-assisted extraction of phenolic compounds from grumixama pulp and peel flour and evaluated the effect of secondary crosslinking time on the mechanical properties of alginate–chitosan films developed as potential materials for wound dressing applications. Grumixama flour (2 g) was extracted with 40 mL of ethanol/water mixtures at different ratios (100:0, 75:25, 50:50, 25:75, and 0:100, v/v) using an ultrasonic processor at 40 °C for 30 min. Extraction yield and total phenolic content were determined, and the extract with the highest phenolic content was incorporated into the alginate–chitosan film-forming matrix. The 50:50 ethanol/water mixture exhibited the highest total phenolic content (30.87 ± 1.54 mg GAE/g), whereas the highest extraction yield was obtained with the 75:25 mixture (42.94 ± 2.67%), indicating that extraction yield was not directly associated with phenolic compound recovery. The phenolic-rich extract was incorporated into the polymeric matrix, and the resulting films were subjected to secondary [GA1] crosslinking for 5, 15, and 25 min. Significant differences in mechanical properties were observed among treatments (p < 0.05). For extract-containing films, tensile strength increased from 9.06 ± 1.28 MPa after 5 min to 18.85 ± 0.79 MPa and 21.47 ± 2.75 MPa after 15 and 25 min, respectively, whereas elongation at break decreased from 3.71 ± 0.67% to 3.66 ± 0.78% and 2.99 ± 0.09%. After 25 min of crosslinking, the extract-containing film exhibited lower tensile strength than the blank film (21.47 ± 2.75 and 28.17 ± 1.06 MPa, respectively), but greater elongation at break (2.99 ± 0.09% versus 1.44 ± 0.35%). These findings indicate that incorporation of the grumixama extract modified the mechanical behavior of the polymeric matrix, while secondary crosslinking time modulated the balance between mechanical strength and extensibility. The combination of an alginate–chitosan matrix with a phenolic-rich grumixama extract represents a promising strategy for developing functional films with potential for wound dressing applications. Further studies addressing physicochemical, antioxidant, antimicrobial, swelling, water vapor permeability, cytocompatibility, and wound-healing performance are warranted to establish their suitability for biomedical applications.