Antibacterial potential of non-volatile constituents of Rosmarinus officinalis against 37 clinical isolates of multidrug-resistant bacteria.

ZAMPINI I.C.; ARIAS M.; CUDMANI N.; ORDOÑEZ R; ISLA M.I.; MORENO S.

Boletín Latinoamericano y del Caribe de Plantas Medicinales y Aromáticas

BLACPMA

Año: 2012 vol. 12 p. 201 - 208

0717 7917

In this paper we investigated the antibacterial activity of a methanolic extract of Rosmarinus officinalis L. and their main constituents, carnosic acid and rosmarinic acid, against 37 nosocomial strains of multidrug-resistant bacteria. Results obtained showed that both the rosemary extract and carnosic acid inhibited all clinical isolates of Staphylococcus aureus methicillin-resistant and Enterococcus faecalis gentamicin and streptomycin-resistant bacteria examined (MICs 60 μg/mL vs. 200 μg/mL, respectively). Rosemary extract showed MIC values between 400 and 1600 μg/ml against the Gram-negative multidrug-resistant bacteria: Escherichia coli, Proteus mirabilis, Enterobacter cloacae, Pseudomonas aeruginosa, Morganella morganii and Providencia stuartii, while carnosic acid showed MIC of 120 to 240 μg/mL. Bactericidal effect of carnosic acid against S. aureus and E. faecalis was observed at their MIC value, while 2 x MIC to 4 x MIC were needed to kill Gram-negative bacteria. Rosmarinic acid showed a narrow spectrum of action against a few Gram-negative clinical isolates. Our findings suggest that carnosic acid would be a good lead candidate useful in counteracting drug-resistant infections.