Antimicrobial activity of Monascus purpureus-derived red pigments against Salmonella typhimurium, Escherichia coli, and Enterococcus faecalis

The rise of antimicrobial-resistant microorganisms (AMR) poses a significant global challenge to human health and economic stability. In response, various scientific communities are seeking safe alternatives to antibiotics. This study comprehensively investigates the antibacterial effects of red dye derived from Monascus purpureus against three bacterial pathogens: Salmonella typhimurium ATCC14028, Escherichia coli ATCC8739, and Enterococcus faecalis ATCC25923. The dye was extracted from the Monascus purpureus ATCC16436 strain, using 1 mg of red dye in 1 ml of DMSO to achieve a concentration of 1000 µg/ml. The chemical profile of the red dye extract was analyzed using GC-MS analysis, confirming the presence of several bioactive antimicrobial compounds, including aspidospermidin-17-ol, 1-acetyl-16-methoxy, octanoic acid, and hexadecanoic acid methyl ester. The extract was tested against the bacterial strains at varying concentrations to determine the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC). The results demonstrated significant antibacterial activity, with the highest MIC and MBC values of 6.25/12.5 µg/ml against S. typhimurium. The antibacterial activity of the red dye was compared to five conventional antibiotics using the disc diffusion method, revealing superior effectiveness, particularly against S. typhimurium, with an inhibition zone measuring 20 ± 0.22 mm. Scanning electron microscopy was employed to explore the mechanism of action of the red dye extract, highlighting its impact on bacterial plasma membrane permeability and its interference with cellular energy production. These findings suggest that the Monascus purpureus-derived red dye extract represents a promising natural alternative to conventional antibiotics, demonstrating potent antibacterial activity and potential as a novel therapeutic agent in combating antimicrobial resistance.