Eco-Friendly Collagen Films: Valorization of Leather Tannery Waste and Bioactive Potential of Hymenaea martiana Extract

The aim of this study was to develop sustainable films based on collagen recovered from tanned leather waste with Hymenaea martiana stem extracts (HMEC) obtained by microextraction, with an emphasis on evaluating their physical and chemical properties. The phytochemical analysis of HMEC revealed a high content of phenolics (396.6 mg of gallic acid equivalents per gram of extract (mg EAG g–1) and flavonoids (296.2 mg of catechin equivalents per gram of extract (mg EC g–1)), with a predominance of flavonoids (74.7%). The liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry (LC-ESI-Q-TOF-MS) characterization evidenced a wide diversity of secondary metabolites, highlighting flavonoids such as fustin, isokaempferide, liquiritigenin, myricitrin, quercitrin, and quercetin derivatives, in addition to compounds such as quinic acid and glycosides. Furthermore, hydrolyzed collagen obtained from leather industry waste was combined with polyvinyl alcohol (PVA), glycerol, and different concentrations of HMEC to produce the films. The films exhibited high tensile strength (3833-4570 mPa), a significant increase in elongation at break (187.5-311.1%), and a swelling rate of up to 624.2% in samples with 3% HMEC, retaining 70% moisture after 18 h. The results highlight the great potential of these films for wound treatment and reinforce the sustainable reuse of leather industry waste.