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. Key words: Piper nigrum, Syzygium aromaticum, antibiotic promotion, Staphylococcus aureus, Salmonella, toxicity.
Highlights
Spices are highly used in Chadian diet and many research works indicate that some of them have biological activities (Beuchat, 1994; Shan et al, 2007)
P. nigrum and S. aromaticum fruits were purchased from local market in N’Djamena (Chad) and stored in vacuum sealed bags. They were identified by the National Herbarium of Cameroon in Yaoundé, where specimens for P. nigrum and S. aromaticum fruits were respectively stored under the reference numbers 25818/SFRcam and 28524/HNC
The results obtained in this work suggested that P. nigrum essential oil (EO) has good synergistic activity in combination with gentamicin and ciprofloxacin, while S. aromaticum EO promotes well, the activity of gentamicin
Summary
Spices are highly used in Chadian diet and many research works indicate that some of them have biological activities (Beuchat, 1994; Shan et al, 2007). In the continuous search for natural compounds with antimicrobial properties, a more safety approach is to use substances already belonging to human diet. Bacterial infection is one of the most current causes of illness worldwide (Kuete, 2013) and especially in developing countries (Adwan et al, 2008). According to Havelaar et al (2015), food borne diarrheal disease agents, non-typhoidal Salmonella enterica, cause about 23000 death worldwide, with a high percentage in Africa. Salmonella Typhi was recognized as one of the major cause of food borne diseases. Regarding Staphylococcus aureus, Tong et al (2015) stated that in the industrialized world, the population incidence of S. aureus bacteremia ranges from 10 to 30 per 100,000 person/year
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