Composition and antioxidant and antifungal activities of the essential oil from Lippia gracilis Schauer

In this study, the oil constituents of Lippia gracilis were identified by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The antioxidant and antifungal activities were also evaluated. The leaf oil showed a yield of 3.7% and its main constituents were thymol (70.3%), p-cymene (9.2%), thymol methyl ether (5.4%) and p-methoxythymol (2.7%). The thin stem oil showed a yield of 0.4% and its major components were thymol (70.1%), thymol methyl ether (4.4%), p-methoxythymol (4.0%), p-cymene (3.8%), α-humulene (2.4%) and (E)-caryophyllene (2.1%). The aromatic monoterpenes found in the oils showed an average of 88%. The scavenging activity of the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) for the leaf oil, expressed as half maximal effective concentration (EC50), was 35.7±3.3 µg/ml, indicating high antioxidant activity. The evaluation of fungicide activity for the leaf oil, using direct bioautography, showed also a significant value for lethal concentration (LC50 5.0 μg/ml) against Cladosporium sphaerospermum and C. cladosporioides fungi.   Key words: Essential oil composition, thymol and carvacrol, DPPH radical scavenging and bioautography