Abstract

Chemical composition, in vitro antioxidant and antibacterial activities of essential oil of Lippia sidoides (EOLS) and its major constituent was investigated. Chemical composition was analyzed in a gas chromatograph coupled to a mass spectrometer (GC/MS). Antioxidant activity (AA) was obtained using 2,2-diphenylpicrylhydrazyl (DPPH) radical scavenging assay. Antimicrobial activity was tested using disk-diffusion test against Staphylococcus aureus ATCC 25923 and nine S. aureus strains resistant to beta-lactams, tetracycline and quinolone. EOLS chemical composition revealed the presence of 15 components identified as monoterpenes hydrocarbon (1.56%), oxygenated monoterpenes (94.31%) and sesquiterpenes hydrocarbon (4.11%), and the major components were thymol (79.70%). All OELS concentrations analyzed showed AA varying from 19.09 ± 2.088% (100 µg/mL) to 74.32 ± 1.61% (3.200 µg/mL). For thymol, the most efficient AA (70.11 ± 3.43%) was found with higher concentration (6.400 µg/mL). All S. aureus strains (n = 10) were sensitive to OELS and thymol. When OELS was used, the halo size of the ATCC strain was 74.4 mm and for the resistant-strains, it ranged from 29 to 60.4 mm. Thymol bioactive was lower when compared with OELS: the ATCC strain showed a halo of 24.5 mm and a variation of 17.5 to 45 mm was observed between the halo sizes in resistant strains. The results suggest that OELS as compared to thymol has better potential for use as an antimicrobial and antioxidant agent.

Key words: Antimicrobials, Lippia, thymol, essential oil, 2,2-diphenylpicrylhydrazyl (DPPH), Staphylococcus aureus, oxygenated monoterpenes, antioxidant.