Characterization, antioxidant, and antimicrobial activity of melanin extracted from nigerseed hulls

This study aims to characterize and explore the biological effects of melanin derived from nigerseed (Guizotia abyssinica) hulls, which are inedible. Extracted melanin was selectively soluble in alkali and DMSO. The melanin extract demonstrated robust antioxidant and DPPH radical scavenging activities. It exhibited strong antibacterial effects against foodborne pathogens, as indicated by the zone of inhibition (in mm); Salmonella enterica (40.00 ± 0.00), Staphylococcus aureus (37.33 ± 1.15), Micrococcus luteus (31.67 ± 0.58), Klebsiella oxytoca (31.33 ± 1.15), Escherichia coli (30.33 ± 0.58), and Bacillus cereus (28.33 ± 1.15). For antifungal activity, melanin displayed selectivity, suggesting its potential as a targeted antifungal agent. This research highlights nigerseed byproducts as a cost-effective and promising source for melanin production, showcasing its potential in the pharmaceutical sector as a natural alternative to chemically derived drugs. [Display omitted] •FTIR spectral study revealed common signals in synthetic melanin and melanin from nigerseed hulls (NH).•Melanin from Nigerseed hulls exhibited significant antimicrobial activity against various microorganisms.•DPPH scavenging activity of NH melanin indicated a gradual increase in scavenging with higher melanin concentration.