Antibiofilm, cellular antioxidant, anti-inflammatory, immunomodulatory, cytotoxic, and antimutagenic activities of soluble melanins from Randia echinocarpa fruit

Melanins are widely distributed biopolymers that exhibit important biological activities. However, fruit melanins have been scarcely studied. In this work, the antibiofilm, cellular antioxidant, anti-inflammatory, immunomodulatory, cytotoxic, and antimutagenic activities of soluble melanins (SMs) isolated from the Randia echinocarpa fruit (papache) were evaluated. The SMs inhibited biofilm formation in Staphylococcus aureus MDR and ATCC 43300 up to 60% at 1000 µg/mL; they presented a cellular antioxidant activity (60.02%) at 50 µg/mL, were immunomodulatory by increasing the peripheral blood mononuclear cells (PBMC) proliferation index (1.09 at 50 μg/mL), and inhibited HeLa cell proliferation by 77.39% (IC₅₀ = 9.34 µg/mL). SMs were neither toxic nor mutagenic in the Salmonella Typhimurium YG1024 strain and inhibited the 1-nitropyrene mutagenicity by 30.2%. The biological activities of papache SMs support their potential to be used in nutraceutical and pharmaceutical formulations.