Essential oils are secondary metabolities that are highly concentrated substances extracted from flowers, leaves, stems, roots, seeds, barks, resins, or fruit rinds. Essential oils have been recognized as some of the most promising compounds in the development of novel products particularly in the pharmaceutical, agricultural, food and perfumery industries. Black cumin (Nigella sativa L.) belonging to family Rannunculaceae is an important medicinal plant with worldwide distribution. In Ethiopia, N. sativa occurs in all regions and agro-ecologies at different altitudinal ranges. This research work aimed to extract optimum amount of oil, chemical characterization & determination of the antimicrobial activity of the essential oils from black cumin seeds using Clevenger distillation method. Clevenger distillation extraction process is a popular extraction method and suitable for most plant materials. The Clevenger distillation process is considerably cheap compared to other methods and has potential for commercialization due to its reliability in producing mass oil production. From the results obtained, it was discovered that the black cumin seeds could give the maximum yields of essential oil to be 40.4% w/w can be extracted by steam distillation at the optimum condition of temperature 960C, time 60 min. Furthermore,the volume of essential oil increases with increase in temperature by keeping time of heating as constant and vise versa. The chemical composition of the seed oil was found to be Saponification value (104.9%), Acid value (1.43%),Fatty acid value (1.94%), ioidine (98.16%) and peroxide value (1.56 %) this indicated that it could be used for production of other valuable products in different process industries.All of essential oils were investigated for activity against the microorganisms E. coli, B. cereus,S. aureus, S. typhimurium, L.monocytogenes and E. faecalis,using a disc-diffusion method show a maximal diameter of inhibition zone 19, 10, 12, 12,14, 11 mm respectively.The essential oil from black cumin seed showed the highest antimicrobial activity on all these bacteria. So, the seed oil can be uitilized for industrial and medicinal purpose as well.
Keywords: Essential oils, seeds