Antistaphylococcal and biofilm inhibitory activities of gallic, caffeic, and chlorogenic acids

Abstract

Staphylococcus aureus is a Gram-positive pathogen which is able to form biofilms, exhibiting a more pronounced resistance to antibiotics and disinfectants. The hurdles posed in eradicating biofilms have driven the search for new compounds able to fight these structures. Phenolic compounds constitute one of the most numerous and ubiquitous group of plant secondary metabolites with many biological activities. The aim of the present work was to study the potential antimicrobial and antibiofilm properties of gallic, caffeic, and chlorogenic acids against S. aureus as well to elucidate its mechanism of action. It was concluded that the phenolic acids studied in this work have antistaphylococcal properties. For instance, gallic acid is able to influence the adhesion properties of S. aureus. The phenolic acids tested were also able to inhibit the production of α-hemolysin by this microorganism, with the exception of chlorogenic acid. Regarding its mechanism of action, caffeic acid interferes with the stability of the cell membrane and with the metabolic activity of the cells of S. aureus.

Keywords:

• gallic acid
• caffeic acid
• chlorogenic acid
• S. aureus
• biofilms

Acknowledgments

Ângelo Luís acknowledges a PhD fellowship from Fundação para a Ciência e a Tecnologia (Reference: SFRH/BD/65238/2009), co-funded by the Fundo Social Europeu (POPH – QREN), and by national funds of the Ministério da Educação e Ciência and also Larissa Léa da Silva for the support in part of the experimental work. Filomena Silva acknowledges a postdoctoral fellowship (SFRH/BPD/79250/2011) from Fundação para a Ciência e Tecnologia within the scope of QREN – POPH – Advanced Formation programs co-funded by the Fundo Social Europeu and MEC. The authors also wish to thank Eng. Ana Paula Gomes, from the Centro de Óptica of the Universidade da Beira Interior, for help in SEM image acquisition. This work was partially supported by the project [PEst-C/SAU/UI0709/2011] funded by the Fundação para a Ciência e a Tecnologia through the program COMPETE.