Primarily synthesized for chelating metal ions from the surrounding media, the pyomelanin plays an important role in bacterial virulence where it is needed for infection and biofilm formation as well as protection from host immune response. In this study, two out of three phenolic acids, gallic acid, and propyl gallate induced pyomelanin in two clinical isolates of Pseudomonas aeruginosa and inhibited biofilm formation. Ascorbic acid treatment reversed the gallic acid and propyl gallate mediated pyomelanin synthesis without reversing the inhibition of the biofilm formation. mRNA expression study revealed the upregulation of homogentisic acid oxidase enzyme by ascorbic acid treatment, possibly contributing towards the inhibition of pyomelanin synthesis. Tannic acid did not show any antibacterial or pyomelanin-induction activities. The synergistic effect of gallates and ascorbic acid in the inhibition of biofilm formation and associated pyomelanin synthesis was evidenced which needs further studies to establish their antibacterial efficacies, especially against the clinical isolates of Pseudomonas sp.

主要合成用于从周围介质中螯合金属离子，脓黑色素在细菌毒力中起着重要作用，感染和生物膜形成以及防止宿主免疫反应需要它。在这项研究中，三分之二的酚酸、没食子酸和没食子酸丙酯在两种铜绿假单胞菌临床分离株中诱导了脓黑色素并抑制生物膜的形成。抗坏血酸处理逆转了没食子酸和没食子酸丙酯介导的脓黑色素合成，而没有逆转对生物膜形成的抑制。mRNA 表达研究揭示了抗坏血酸处理可上调 homogentisic 酸氧化酶，这可能有助于抑制脓黑色素合成。单宁酸没有表现出任何抗菌或诱导脓黑色素的活性。证明了没食子酸酯和抗坏血酸在抑制生物膜形成和相关的脓黑色素合成方面的协同作用，需要进一步研究以确定它们的抗菌功效，特别是对假单胞菌的临床分离株。