Lippia sidoides Cham. (Verbenaceae) is used in the folk medicine as topical antiseptic in skin and mucous membranes and its therapeutic effect is attributed to the thymol presence. The objective of this work was to verify the chemical composition and antibiotic modifying activity of the essential oil extracted from the leaves of L. sidoides and its major component thymol. The essential oil was obtained by hydrodistillation and analyzed by GC/MS. The synergistic activity was evaluated using gaseous contact method. The essential oil was obtained (yield of 1.06%) and the GC/MS analysis identified the main constituents: thymol (84.9%) and p-cymene (5.33%). The antibiotic modifying activity was verified using the minimal inhibitory dose method and gaseous contact. It verified the interference of essential oil and thymol against all tested aminoglycosides. There were no statistical differences between the activity of the essential oil and thymol against Pseudomonas aeruginosa, indicating this to be the responsible composition for such activity. However, the oil was shown more effective when compared to the thymol against Staphylococcus aureus. The essential oil of L. sidoides and its major component thymol influence the activity of aminoglycosides and may be used as adjuvant in antibiotic therapy against respiratory tract bacterial pathogens.

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This work reports the chemical composition of the essential oil of Lippia sidoides (EOLS) and evaluation of the topical effect of EOLS and thymol against different irritant agents in vivo. The essential oil was obtained by hydrodistillation, and gas chromatography/mass spectrometry analysis identified the main constituents: thymol (84.9%) and p-cymene (5.33%). The antiinflammatory activity was evaluated using the mouse models of acute ear inflammation induced by croton oil, arachidonic acid, phenol or histamine, and chronic inflammation induced by croton oil. The topical application of EOLS or thymol at a dose of 2 mg/ear significantly reduced (p < 0.001) ear edema induced with arachidonic acid by 45.1% and 47.4% and reduced ear edema induced with phenol by 33.2% (p < 0.05) and 54.7% (p < 0.01) in acute ear edema. However, a proinflammatory effect of EOLS and thymol was evidenced when it was applied for more than 1 day. There were no statistical differences in antiedematogenic activity between EOLS and thymol. In conclusion, the results indicate that thymol is the constituent responsible for the topical antiinflammatory activity of EOLS. Thus, these findings could justify the popular use of L. sidoides by alternative medicine, but chronic use has an inflammatory effect.

The species Lippia sidoides Cham. (Verbenaceae) is utilized in popular medicine as a local antiseptic on the skin and mucosal tissues. Enterococcus faecalis is the bacterium isolated from root canals of teeth with persistent periapical lesions and has the ability to form biofilm, where it is responsible for the failure of endodontic treatments. Essential oil of L. sidoides (EOLS) and its major component, thymol, were evaluated for reducing the CFU in biofilms of E. faecalis in vitro. The essential oil was obtained by hydrodistillation and examined with respect to the chemical composition, by gas chromatography-mass spectrometry (GC-MS). The GC-MS analysis has led to the identification of thymol (84.9%) and p-cymene (5.33%). EOLS and thymol reduced CFU in biofilms of E. faecalis in vitro (time of maturation, 72 h), with an exposure time of 30 and 60 min at concentrations of 2.5 and 10%. There was no statistical difference in effect between EOLS and thymol, demonstrating that this phenolic monoterpene was the possible compound responsible for the antimicrobial activity of EOLS. This study provides a basis for the possible utilization of EOLS as an adjuvant in the treatment of root canals that show colonization by E. faecalis.