Rosmarinic acid–Modes of antimicrobial and antibiofilm activities of a common plant polyphenol.

• Antimicrobial potential of rosmarinic acid confirmed towards 11 Candida strains and 13 bacterial pathogens. • Antibiofilm properties include inhibition of Candida attachment, eradication of established biofilms, moderate reduction of exopolysaccharide production. • Antimicrobial mechanisms include disturbance in mitochondria activity and cell membrane integrity, moderate reduction in protease production but not binding to ergosterol. Emerging antimicrobial resistance and side effects associated with antibiotics overuse are driving the need for the novel antimicrobial therapeutics with the natural compounds considered as an appealing alternative. Rosmarinic acid is abundantly present in medicinal plants. This study aimed to elucidate its possible role as an inhibitor of planktonic and biofilm microorganism growth, along with its antifungal mechanisms. In this study, rosmarinic acid showed promising anticandidal (MIC 0.1–0.2 mg/mL) and antibacterial (MIC 0.002->0.8 mg/mL) activity. To some extent it was able to prevent cell attachment and eradicate established biofilms. Rosmarinic acid antifungal mechanisms included reduction of mitochondrial activity, alteration in membrane integrity, and slight inhibition of protease production but not binding to ergosterol. Its antibiofilm activity was moderately linked to the reduction in exopolysaccharide production. Considering its wide antimicrobial and antibiofilm spectrum rosmarinic acid could be further explored as an antimicrobial agent along with range of medicinal plants with rosmarinic acid as the dominant compound. Nevertheless, rosmarinic acid could serve as the basis for the development of antimicrobials employing novel mechanisms of activity. [ABSTRACT FROM AUTHOR]