COMPOSITION AND ANTIMICROBIAL ACTIVITY OF Lippia origanoides ESSENTIAL OIL UNDER ELICITATION

Lippia origanoides Kunth (Verbenaceae) is a native medicinal herb that produces essential oil with wide antimicrobial activity, but the production of bioactive volatile terpenes would vary depending on the environmental conditions. A way to investigate environmental conditions on secondary metabolism production is to use elicitors: agents that stimulate the plant defense metabolism. Therefore, the aim of this work was to evaluate the effect of elicitors on the essential oil production, composition and antimicrobial activity of L. origanoides against Escherichia coli CCMB261 (sulphonamide-resistant), Candida albicans CCMB286 (fluconazole and amphotericin B resistant) and Staphylococcus aureus CCMB263 (novobiocin-resistant). To this end, field cultivated plants were sprayed with sterile cell material suspensions of Aspergillus niger (AN) and Fusarium oxysporum (FO), hydrogen peroxide solution (SH2O2) and distillated water (CT). The three clinical pathogens were obtained from Microorganisms Culture Collection of Bahia (CCMB/UEFS) and the two phytopathogenic filamentous fungi from the Laboratory of Phytopathology of Federal University of Recôncavo da Bahia (UFRB). The essential oils of dry leaves (LEO) and inflorescence (IEO) were hydrodistillated, and the volume were used to calculate the essential oil percentage (EO%) and yield corresponding to the plant weight. The composition was determined through gas chromatography coupled to mass spectrometry (CG-MS). The antimicrobial activity was determined by broth microdilution method with different oil concentrations (9.5 to 0.074 µL/mL) and the minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and minimal fungicide concentration (MFC) were determined. The treatments did not modify the LEO production and composition. SH2O2 raised the IEO production. FO increased the IEO bicyclogermacrene content. All elicitors tended to increase the antimicrobial activity against Candida albicans and Staphylococcus aureus, and to reduce the activity against Escherichia coli of both essential oils. Although no statistical difference was detected in the concentration of LEO components between the treatments, the small variation was sufficient to determine the change in the efficiency of the antimicrobial activity. These results show that SH2O2, FO and AN spraying could promote the elicitation of antimicrobial volatile terpenoids production of L. origanoides.