Chemical composition, antibiotic promotion and in vivo toxicity of Piper nigrum and Syzygium aromaticum essential oil

Abstract

The antimicrobial activity of spices of human daily diet has been widely demonstrated. Yet, their capacity of promoting antibiotic activity has not been explored adequately. In this work, the chemical composition of essential oils of Piper nigrum and Syzygium aromaticum from Chad were determined and their antimicrobial effect in combination with different antibiotics towards Staphylococcus aureus, Salmonella enteritidis and Salmonella typhi were assessed. Moreover, the in vivo toxicity of the essential oils alone and in combination with antibiotics was performed. Results indicate that the essential oil of P. nigrum was mostly composed of limonene (18.59%), beta-pinene (11.51%), linalool (10.17%), alpha-pinene (9.96%), while for S. aromaticum essential oil, only three compounds represented about 89% of the identified compounds. They were respectively beta caryophyllene (43.63%), eugenol (42.67%) and alpha-humulene (3.73%). Regarding the antimicrobial properties, Syzygium aromaticum essential oil (EO) used alone was more active than P. nigrum EO with a minimum inhibitory concentration (MIC) of 625 ppm towards all the strains. In combination with selected antibiotics, S. aromaticum gave better results with less indifference association, the best being with gentamicin. This association of the different EOs with gentamicin proved not to be acutely toxic to rats after 14 days of observation at doses ten times the MIC. These results indicated that spices used in human diets can be used for the production of hybrid drugs containing antibiotic and natural substances.