Evaluation of Antimicrobial Efficacy of Ethanol Extracts of Fresh Citrus sinensis (Sweet Orange) Seeds against Selected Bacterial Strains

The antibacterial activities of fresh Citrus sinensis seed oil and non-oil extract are investigated in this study. Gram positive (Staphylococcus aureus and Enterococcus faecalis) and Gram negative (Pseudomonas aeruginosa, Escherichia coli and Salmonella spp.) bacterial strains are used in this study and antibacterial activity is estimated using the agar well diffusion method. Zones of inhibition were measured and the minimum inhibitory concentration and minimum bacteriostatic concentrations were determined. The results show that the non-oil extract had better antibacterial activities against Staphylococcus aureus, Enterococcus faecalis and Escherichia coli compared to the oil extract (zones of inhibition at 200 μg/ml of 12 mm, 8 mm and 2 mm respectively for the nonoil extract; 4 mm, 6 mm, 0 mm respectively for the seed oil). The seed oil however had better antibacterial activity compared to the non-oil extract in Salmonella spp. (zones of inhibition at 200 μg/ml of 8 mm for the seed oil compared to 4 mm for the non-oil extract). Pseudomonas aeruginosa showed similar susceptibility to both extracts at both concentrations studied (zones of inhibition of 4 mm and 2 mm for both extracts at 200 μg/ml and 100 200 μg/ml respectively). Minimum inhibitory concentrations ranged from 50 – 100 μg/ml while minimum bacteriostatic concentrations ranged from 100 – 200 μg/ml. We conclude from our findings that both extracts hold promise in the development of antimicrobial therapeutics. Keywords: Citrus sinensis, Antibacterial, minimum inhibitory concentration, minimum bacteriostatic concentration