Bio-chemical studies on some essential oils as anti – microbial and anti – oxidant agents

The relationship between man and plants has been very close throughout the development of human cultures. At no time in development of mankind, however has there been more rabid and more deeply progress in our understanding of plants and their chemical constituents than during the past quarter of this century. The use of synthetic antimicrobial has severe side effects especially with those tested for antibacterial. Therefore, it is useful to return to the natural products from medicinal and aromatic plants to overcome the side effects of synthetic antimicrobial agents. To achieve this goal eight essential oils were chosen as a source of a natural antimicrobial agents, lemongrass, eucalyptus, peppermint, thyme, clove, oregano, cinnamon and rosemary. The major compound found in lemongrass essential oil, was D-limonene (54.01%). Seventeen compounds were identified in eucalyptus essential oil. The major compound found in peppermint essential oil, were carvone (59.42%). The major compound found in oregano essential oil, was terpinene 4-ol (36.06%). The major compound found in thyme essential oil, was thymol (48.06%). Benzyl Alcohol is the major compound (51.67%) in clove essential oil.  cinnamaldehyde was the major compound (61.87 %) in the cinnamon essential oil. The major compound found in rosemary essential oil, was (1,8-Ccneole 32.5%). The antioxidant potential of lemongrass, eucalyptus, peppermint, oregano, thyme, clove, cinnamon and rosemary essential oils were further highlighted by the quenching of DPPH free radicals. Lemongrass essential oil showed the strongest radical-scavenging effect (69.97%) at 50 g/L, which is lower than those observed for the positive controls, ascorbic acid (92.68 %). The antimicrobial activity of the investigated essential oils was tested against six bacterial (three gram +ve bacteria and three gram -ve bacteria) and two fungal strains including gram positive gram negative and two fungal.