Investigation of antibacterial and antifungal activities of essential oils of Lippia javanica and Lantana camara (Verbenaceae) harvested in the Haut-Katanga (DR Congo)

Abstract

Background: Essential oils are volatile compounds characterized by a strong odor, and are generally biosynthesized by aromatic plants as secondary metabolites. This paper aims to extract the essential oils of Lippia javanica and Lantana camara, and to evaluate their antibacterial, and antifungal activities. Methods: The aerial parts of Lippia javanica and Lantana camara were subjected to hydrodistillation to produce the essential oil. The antimicrobial potential was characterized against six microorganisms, signifying three Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa), two Gram-positive bacteria (Staphylococcus aureus and Streptococcus pneumoniae) and one fungus(Candida albicans) by the disc diffusion method to determine the inhibition zone (in mm) and dilution method to determine the minimal inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Results: Essential oil extraction was carried out with an average yield of 0.21% for Lippia javanica, and 0.11% for Lantana camara. The evaluation of the antimicrobial activity showed that Lippia javanica essential oil had a moderate inhibitory activity on Klebsiella pneumoniae, and Streptococcus pneumoniae (MIC: 0.76 mg/mL), on Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa (1.50 mg/mL). The Lantana camara essential oil showed weak inhibitory activity against all strains tested. By diffusion disk method, it was found that Klebsiella pneumoniae was the most sensitive on Lippia javanica essential oil with an inhibition diameter, which evolved from 7 mm to 24 mm; followed by Pseudomonas aeruginosa (21 mm), Escherichia coli (19 mm) and Streptococcus pneumoniae (13 mm) at 15 μL. By means of dilution method, the Lantana camara essential oil showed a low activity against Escherichia coli (MIC: 1.64 mg/mL), Klebsiella pneumonia (MIC: 1.64 mg/mL), Staphylococcus aureus (MIC: 3.28 mg/mL), Pseudomonas aeruginosa (MIC: 3.28 mg/mL), and Candida albicans (MIC: 3.28 mg/mL) but by disc diffusion method, this oil was slightly inhibitory activity on Escherichia coli (10 mm at 15 μL). For the antifungal activity, the Lantana camara essential oil, and Germicide were inactive on Candida albicans when tested by the disk method. Conclusion: The essential oil of Lippia javanica showed moderate antibacterial and antifungal activities, while the essential oil of Lantana camara showed low activity. The activities of essential oils studied were less than that of the gentamicin and more than the activity of Germicide, with two positive controls used.