Enhancement of aminoglycosides and β-lactams antibiotic activity by essential oil of Lippia sidoides Cham. and the Thymol

Abstract

Natural products from plants can alter the effect of antibiotics, by increasing or reducing its activity. Lippia sidoides Cham. (Verbenaceae) is a bush found in the Northeastern region of Brazil. In popular medicine, L. sidoides has been used as antiseptic. In this work we report the chemical composition of the essential oil from L. sidoides and to determine the potentiation of the activity of aminoglycosides and β-lactams. The essential oil of L. sidoides was extracted by hydrodistillation using a Clevenger. The composition of the essential oil was determined by GC/MS. The determination of the Minimum Inhibitory Concentration (MIC) and the modulatory activity was realized using microdiluition method. The essential oil showed as major compounds the thymol (84.9%), Etil-methyl-carvacrol (5.33%) and p-cymene (3.01%). The determination of the Minimum Inhibitory Concentration (MIC) by microdiluition demonstrated no difference in the antimicrobial activity between the essential oil (EOLS) and thymol. There was reduction in the MIC of the amynoglicosides gentamicin and neomycin when associated to EOLS and thymol. When the natural products were associated with the β-lactam Penicillin G and Ceftriaxone, the MIC was reduced against Streptococcus mutans and Enterococcus faecalis. The results demonstrated that the thymol is the compound responsible for the antimicrobial activity and in modifying the antibiotic activity in vitro of the EOLS. More studies are necessary in order to evaluate the behavior of that association alive into verify the biodisponibility and the possible toxic effects.

Keywords

• Lippia sidoides
• Thymol
• Antibacterial activity
• Modifying antibiotic activity