Effect of Solvents on Phytoconstituents and Antimicrobial Activities of Ocimum gratissimum and Eugenia caryophyllata Extracts on Listeria monocytogenes

This study examined the effect of different solvents on active ingredients and antimicrobial performance of fresh leaves of Ocimum gratissimum and dried buds of Eugenia caryophyllata. Plant parts were extracted in a soxhlet apparatus using dietyl-ether, ethyl acetate, and ethanol. Phytoconstituents of the plants was determined using gas chromatography-mass spectrometer (GC-MS). The extract with high eugenol concentrations was prepared in seven treatments (160, 80,40, 20, 10, 5, and 0 mg/mL) and tested against Listeria monocytogenes using agar well diffusion methods in triplicates. Minimum inhibitory concentration (MIC) and zone of inhibition were determined using standard technique. The data was subjected to descriptive statistics and one-way analysis of variance (ANOVA) at alpha 0.05. The results showed that the phytochemical concentration of the extract varied significantly (p<0.05) with respect to solvents. Extract of E. caryophyllata using ethyl acetate had highest concentration of eugenol (71.32%) while O. gratissimum had 16.67%. The results revealed anti-L. monocytogenes activities of fresh leaf of O. gratissimum and dried buds of E. caryophyllata capacity with zones of inhibition of 13.33 mm and 19.00 mm respectively and MIC of 80 mg/ml. This establishes the possibility of using fresh leaf of O. gratissimum and dried buds of E. caryophyllata to prevent the growth of food borne bacterias, especially L. monocytogenes.