Storage Properties of Double-Layer Films Enriched with <i>Phytolacca americana</i> L. Extract as Active Packaging for African Catfish, with a New Approach to Antioxidant Film Assay and Additional Analysis of <i>P. americana</i> Extract Toxicity on Human Cell Lines

Novel double-layer films based on furcellaran (FUR) and gelatin (GEL) with the addition of <i>Phytolacca americana</i> L. (PA) extract were used as active packaging for African catfish fillets. Films with PA extract have been shown to minimize the catfish spoilage effects, expressed as odor reduction compared to control samples; however, neither the films nor the PA extract exhibited antimicrobial activity against tested groups of microorganisms (fungi, lactic acid bacteria, <i>Enterobacterales</i> and psychrotrops) or specified microorganisms (<i>E. coli</i>, <i>S. aureus</i>, <i>S. cerevisiae</i>). The tested films demonstrated antioxidant activity determined by the DPPH, ABTS, FRAP, CUPRAC and Folin–Ciocâlteu methods. Cytotoxicity analysis showed that the PA extract affected tested cell lines (PNT2—prostate epithelial cells, HepG2—human liver cells, HaCaT—normal human keratinocytes and Nty-hori 3-1) only to a small extent—the calculated IC₅₀ values exceeded the maximal tested concentration of 500 µg/mL.