Paul-Georges Rossi, Liliane Berti, Jean Panighi, Anne Luciani,* Jacques Maury, Alain Muselli, Dominique de Rocca Serra, Marcelle Gonny and Jean-Michel Bolla

Abstract: The antimicrobial activity of 28 essential oil samples isolated from local plants or plants cultivated in Corsica was evaluated against a large panel of human pathogenic bacteria, including Campylobacter jejuni which appeared as a good model for this purpose. The chemical composition of the 18 oils selected for their efficiency was determined by GC and GC/MS. Among them, the oils of Cistus ladaniferus, Crithmum maritimum, Daucus carota, Juniperus communis, Mentha aquatica and Santolina corsica showed compositions without components known as active, suggesting the presence of compounds not previously described as antibacterial agents.

Plant material remains an important resource to combat serious diseases over the world. Pharmacognosis investigations of plants are carried out to find novel drugs or templates for the development of new therapeutic agents. Among more than 250,000 species of higher plants, only about 5-10% are chemically investigated. Since many drugs, e.g. quinine and artemisinin (1), taxol and campothecin (2), have been isolated from plants, and because of increased resistance of many microorganisms towards established drugs (3), investigations of the chemical compounds within traditional plants become necessary. It is now well established that bacterial resistance to antibiotics is a serious problem of public health that concerns almost all antibacterial agents and that manifests in all fields of their application. The two factors contributing to this phenomenon are the emergence of resistant bacteria under the selective pressure of the antibiotics, abundantly used in human and veterinary medicine, and the diffusion of resistant bacteria in the different ecosystems (3). The search for new agents has therefore become indispensable. Plant essential oils show antimicrobial activity against a wide range of bacteria including antibiotic resistant species and fungal species (4). They can affect both Gram positive and Gram negative bacteria in addition to yeasts and filamentous fungi (5,6). The essential oils as antimicrobial agents present two main characters: the first, is their natural origin, which means more safety to the people and the environment. The second, is that they have been considered at low risk for resistance development by pathogenic microorganisms (7). In an ongoing project which aims to identify plant derived essential oils products from the island of Corsica for their antimicrobial activities against Gram positive and Gram negative bacterial pathogens, a study of the bactericidal activity of plant essential oils is undertaken. In previous studies characterization of essential oil constituents was carried out in our laboratory (8-10). We have reported that endemic plants from Corsica had specific composition and that several plant species showed a specific composition while growing on the island. This might suggest specific activity of essential oils obtained here. In view of these findings we have hypothesized that Corsican oils contain specific molecules that may act as antimicrobial agents. We further aimed to identify structural feature in the oil constituents that may be responsible for these activities.