Evaluation of antibacterial and antioxidant effects of cinnamon and clove essential oils from Madagascar

Africa is one of the richest continents in floral biodiversity in the world because of its geographical spread. It's estimated to contain almost 40 000 - 45 000 plant species. Cinnamomum zeylanicum (cinnamon) and Eugenia caryophyllus (clove) are two plants imported by Morocco and have a wide range of application, especially in traditional cuisine. The purpose of this study was to determine the antioxidant and the antibacterial properties of C. zeylanicum and E. caryophyllus essential oils. The bacterial inhibiting activity was evaluated against 3 bacterial strains isolated from foods and 4 bacteria referenced ATCC using agar-disc diffusion and broth macrodilution methods, while the antioxidant effect was assessed by DPPH assay. The results of the cinnamon essential oil prove that the disc diffusion method shows an important antibacterial activity against all tested bacteria with inhibition zones at 29.66 +/- 1.7mm for Pseudomonas putida isolated from food and 77.66 +/- 3.8 mm for Pseudomonas aeruginosa ATCC. The Minimum Inhibitory Concentration (MIC) was equal to 1.25 mu L/ml for all bacteria and the Minimum Bactericidal Concentrations (MBC) were between 1.25 mu L/ml and higher than 80 mu L/ml. Regarding the clove results, the inhibition zones were between 14.6 +/- 1.7mm and 35.6 +/- 2.7mm for pseudomonas putida and Pseudomonas aeruginosa ATCC, respectively. The MICs were between 1.25 and 10 mu L/ml and the MBCs between 5 mu L/ml and higher than 80 mu L/ml. Free radical scavenging potentials showed values for IC50 in the order of 1.1 and 1.8 mu L/ml for cinnamon and clove essential oils respectively, which are close to the synthetic antioxidant (BHA) with an IC50 of 0.7 mu L/ml.