Experimental and theoretical studies on antioxidant and antibacterial properties of chitosan-gelatin functional composite films loaded with flavonoids.

Chitosan-gelatin-flavonoid functional composite films were prepared with chitosan, gelatin, and three flavonoids (Naringenin, Apigenin, and Luteolin). The effect of three flavonoids on physical, antioxidant, and antibacterial properties of functional composite film was investigated from experimental and Density functional theory (DFT) simulations. The tensile strength, thermal stability, water solubility, water vapor permeability, antioxidant activity, and antibacterial activity of chitosan-gelatin-flavonoid functional composite films were improved with flavonoid (Naringenin, Apigenin, and Luteolin) incorporation. The release behavior of Apigenin from functional composite film was much lower than that of Naringenin or Luteolin. ABTS+ radical scavenging ability values of functional composite films followed: Luteolin (69.53 %) > Naringenin (41.39 %) > Apigenin (36.13 %). The antibacterial activities of functional composite films against Staphylococcus aureus followed: Luteolin (52.03 mm) > Apigenin (49.34 mm) > Naringenin (43.15 mm). The total number, location of hydroxyl groups on ring-B, and the unsaturation degree on pyrone ring of flavonoids influenced antioxidant and antibacterial activities of functional composite films. The minimum bond dissociation enthalpy values of flavonoids followed: Luteolin < Apigenin < Naringenin. The interaction energy of Apigenin-chitobiose was stronger than that of Naringenin or Luteolin. These results will shed light on flavonoid selection for functional composite films of food packaging.