The essential oils from the leaves of Lippia oreganoides collected in June 2003 (rainy season) and February 2004 (dry season) were analyzed by GC/MS. Thymol (61.9% and 44.7%, respectively) and carvacrol (7.9% and 16.8%, respectively) proved to be the major constituents of both collections. Linalool (0.4%) was present only in the collection made in June 2003, while carvacryl acetate (0.6% and caryophyllene oxide (1.6%) were only detected in the February 2004 collection.

The essential oil obtained from the leaves of Lantana camara var. moritziana (Otto & Dietr.) López-Palacios collected at Rubio, Táchira State, Venezuela, was obtained by hydrodistillation in a Clevenger trap (0.1% yield). The oil was analyzed by gas chromatography-mass spectrometry (GC/MS) on HP GC-MS System, model 5973, identifying 33 compounds (97.1%) of which the major components were germacrene D (31.0%), followed by β-caryophyllene (14.8%), α-phellandrene (6.7%), limonene (5.7%) and 1,8-cineole (5.2%). Evaluation of the antibacterial activity by agar diffusion method with discs against international reference bacteria (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Salmonella Typhi, Pseudomonas aeruginosa) showed growing inhibition of E. faecalis and S. aureus at MIC of 350 mg/mL and 400 mg/mL, respectively.