Superior plants synthetize a great number of chemical substances, defined “secondary metabolites”, which are able to own biocide action that have a great interest in the field of crops protection. Such natural substances are complementary to those compounds produced by chemical synthesis that today are widely utilised and that are a great problem as their impact is negative either for environment or consumers and farmers health. In consideration of the above mentioned issues and also taking into account the significant diffusion on a more and more increasing areas of “biological” cultures, where the use of synthesis molecules having a biocide action is forbidden or, anyway, limited by present rules, the research on new molecules of natural origin holding a valuable biocide action is gaining a great interest. Purpose of this work is: - to select suitable vegetable sources to obtain extracts of natural substances having a biocide action, specifically antifungal, in order to use them in crops protection; - the extraction of these substances with an innovative process, supercritical CO2, without the use of organic solvents. After an deep bibliographical study on phytochemical profile if possible vegetable sources, three Mediterranean plants have been selected: - Olive tree (Olea europaea sativa L.); - Sweet orange tree (Citrus sinensis Osbeck); - Laurel (Laurus nobilis L.). Leaves have been dried and processed with supercritical CO2 (CO2-SC) in order to extracts compounds with antimicrobial properties. For this purpose we utilise: - A laboratory supercritical fluid extractor (“Dionex 703-SFE”); - A supercritical CO2 pilot plant (“Luwar”). On the same leaves steam extractions with a Clevenger have been made in order to compare the antifungal action of the extracts. Extracts undertook biological tests for the in vitro study of their antifungal activity on a collection of phytopathogen fungi isolated from various species of naturally infected plants of agrarian interest. The antifungine efficacy has been compared among the extracts obtained from the same leaves handled with different extraction techniques. The outcomes of our research confirmed the existence of a more antifungine efficacy of the extracts coming from C. sinensis and L. nobilis achieved with supercritical CO2 at operational conditions of 110 bar and 40°C, and also from extracts of O. europea sativa achieved with the same technique at 500 bar and 50°C. The “range” of extracts concentration where a better antifungine activity has been detected is the one from 80 to 800 μg/ml. Experimental tests of extraction with supercritical CO2 both with laboratory extractor and pilot plant and, also, the extraction with Clevanger have been carried out at the laboratories of Casaccia Research Centre of ENEA by the U.T.S. BIOTEC (Biotechnologies, health and ecosystem protection) – BIOTEC-AGRO and BIOTEC-SIS groups. Biological tests on extracts have been carried out at the laboratories of Trisaia Research Centre of ENEA by the U.T.S. BIOTEC Biotechnologies, health and ecosystem protection) – BIOTEC-AGRO group.